Optimized fertilization method for straw returning to field

Abstract

The invention relates to the technical field of agricultural planting, in particular to a straw returning optimized fertilization method. The method comprises the following steps: cutting corn straws into small sections, and carrying out air drying treatment; then, the air-dried corn straw is flatly laid at the 20-30 cm position of the planting field; after straw returning to the field, base fertilizer is applied in combination with ploughing operation. The corn straw is cut into sections and air-dried, so that the contact area between the straw and microorganisms is increased, attachment and decomposition of the microorganisms are facilitated, and a proper living environment is created for the microorganisms. Base fertilizer is applied in combination with cultivated land after straw returning, on one hand, mass propagation of microorganisms is promoted, and the straw decomposition capacity of the microorganisms is enhanced; on the other hand, the straw, the soil and the base fertilizer are fully mixed, nutrients generated by straw decomposition are evenly distributed in the soil and absorbed and utilized by corn roots in time, the problems that straw decomposition is slow and the corn competes for nutrients and water are solved, normal growth of the corn is guaranteed, effective utilization of the straw is achieved, and good promotion of corn growth is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural planting, and in particular to a method for optimizing fertilization by returning straw to fields. Background Art

[0002] With the rapid development of agriculture in my country, ensuring the stable growth of grain production is crucial to national food security. As one of the important grain crops in my country, the increase of corn production has always been the focus of research in the agricultural field.

[0003] In the current corn planting process, there are many challenges that affect yield. On the one hand, the traditional fertilization method is irrational. In the past, fertilization often lacked precision and failed to fully consider the soil fertility and the nutrient demand characteristics of crops at different growth stages. For example, excessive fertilization not only causes waste of resources and increases production costs, but may also cause soil environmental pollution and affect the ecological balance of the soil; while insufficient fertilization cannot meet the nutrients required for corn growth and development, which directly restricts the increase in corn yield.

[0004] On the other hand, soil quality issues are becoming increasingly prominent. Long-term unreasonable farming and planting patterns have destroyed soil structure, reduced fertility, and weakened water and fertilizer retention capabilities. This makes it difficult for corn roots to grow and develop in a good soil environment, which in turn affects the overall growth of the plant and the final yield.

[0005] At the same time, corn stalks are a large amount of waste from agricultural production. If they are not handled properly, it will not only cause a waste of resources, but also have a negative impact on the environment. The traditional method of burning stalks will produce a lot of smoke and dust, pollute the air environment, and destroy the surface structure of the soil, reducing soil fertility. If the simple method of returning stalks to the field is not handled scientifically and reasonably, the stalks will decompose slowly in the soil and it will be difficult to quickly provide effective nutrients for corn growth. It may even compete with corn for nutrients and water in the soil during the decomposition process, affecting the normal growth of corn.

[0006] Under the existing technology, although there are some methods for corn planting and fertilization, these methods fail to effectively integrate various factors and comprehensively solve the above-mentioned problems, making it difficult to achieve further substantial increases in corn yields.

[0007] Therefore, there is an urgent need for a scientific, reasonable, comprehensive and effective planting method that can improve soil quality, rationally utilize straw resources, optimize fertilization strategies, improve fertilizer utilization, and thus increase corn yields. Summary of the invention

[0008] 1. Technical issues to be resolved In view of the existing technology, how to overcome the technical problem that straw decomposes slowly in the soil, is difficult to quickly provide effective nutrients for corn growth, competes with corn for nutrients and water in the soil during the decomposition process, and affects the normal growth of corn.

[0009] (II) Technical solution To this end, the present invention relates to a method for optimizing fertilization by returning straw to fields, comprising: Cut corn stalks into small pieces and air-dry them; In October and November of the same year, spread the air-dried corn stalks flat on the planting site at a depth of 20-30 cm; After returning the straw to the fields, apply base fertilizer in combination with tillage operations.

[0010] Furthermore, the nylon mesh bag method is used to return the straw to the field. The straw is put into a 200-300 mesh nylon mesh bag, which is sealed and spread flat on the planting site at a depth of 20-30 cm, with the bags separated by soil.

[0011] Furthermore, when the straw is returned to the field for 1-2 years, the nitrogen application rate is 188.8-213.9 kg / hm 2 In the case of returning straw to the field for 3-4 years, the nitrogen application rate is 163-194.4 kg / hm 2 between.

[0012] Furthermore, when straw is returned to the field for 1-2 years, the phosphorus application rate is 95-107 kg / hm2. 2 In the case of returning straw to the field for 3-4 years, the phosphorus application rate is 90-100 kg / hm2. 2 between.

[0013] Furthermore, when straw is returned to the field for 1-2 years, the range of potassium fertilizer application is 94.7-110.8 kg / hm 2 In the case of returning straw to the field for 3-4 years, the application range of potassium fertilizer is 78.3-91.4 kg / hm 2 .

[0014] Furthermore, in terms of mass percentage, the ratio of the total amount of quick-acting nitrogen fertilizer to the total amount of slow-release nitrogen fertilizer is (60-63):(37-40).

[0015] Furthermore, the nitrogen fertilizer application method is one of basic fertilization, 40% basic fertilization + 60% topdressing during the jointing period, N40% basic fertilization + 40% topdressing + 20% topdressing during the flowering period, or N40% basic fertilization + 30% topdressing + 15% topdressing during the flowering period + 15% topdressing during the filling period.

[0016] Furthermore, 1-2 weeks before sowing, a bacterial agent solution is prepared according to the ratio of air-dried corn stalks, cellulose-decomposing bacterial agent and nitrogen-fixing bacterial agent of 100: (0.5-1): (0.3-0.5) by mass percentage, and the bacterial agent solution is sprayed on the corn stalks. The treated corn stalks are covered with plastic film and fermented in a pile for 7-10 days.

[0017] Furthermore, after returning the straw to the field and applying the base fertilizer, the surrounding plant residues are collected, crushed and spread on the soil surface; Use a sprayer to spray the fermentation liquid prepared by mixing brown sugar, yeast and water in a mass ratio of 1:1:(8-10) on the laid plant residues.

[0018] Furthermore, after spraying on the soil surface, shallow tillage is performed, and the tillage depth is controlled at 5-10 cm.

[0019] (III) Beneficial effects The beneficial effects of the present invention are as follows: the present invention mentions a method for optimizing fertilization by returning corn stalks to the fields, comprising: cutting corn stalks into small sections and air-drying them; in October-November of the same year, spreading the air-dried corn stalks flat at a depth of 20-30 cm in the planting site; and applying base fertilizer in combination with tillage operations after returning the straw to the fields.

[0020] The method mentioned in this application effectively overcomes the problems that arise during the process of returning straw to the field through multi-step synergy. First, the corn stalks are cut into small sections and air-dried to increase the contact area between the stalks and soil microorganisms, making the stalks easier to be attached and decomposed by microorganisms. In October-November of the same year, the air-dried corn stalks are spread flat at a depth of 20-30cm in the planting area, so that the stalks are in a relatively stable and suitable soil environment for microbial activity. Soil microorganisms grow actively under suitable temperature and humidity conditions, accelerating the decomposition process of the stalks. After the stalks are returned to the field, basal fertilizer is applied in combination with cultivated land operations. On the one hand, basal fertilizer provides rich nutrients for soil microorganisms, which helps microorganisms to multiply in large numbers and further enhances their ability to decompose the stalks; on the other hand, cultivated land operations fully mix the stalks with the soil and basal fertilizer, ensuring that the nutrients produced by the decomposition of the stalks can be evenly distributed in the soil, and promptly absorbed and utilized by the corn root system, avoiding the problem of slow decomposition of the stalks and competing with corn for nutrients and water, thereby ensuring that corn can grow normally in a good soil environment, achieving effective utilization of straw resources and good promotion of corn growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the dynamic changes in corn straw decomposition in Example 1 of a straw return to field optimization fertilization method mentioned in this application, Figure 1 -A represents the schematic diagram of the dynamic changes in corn straw decomposition from 2018 to 2019. Figure 1 -B represents the schematic diagram of the dynamic changes of corn straw decomposition from 2019 to 2020; Figure 2 This is a schematic diagram of the dynamic change process of the carbon release rate of corn straw in Example 1 of a straw return to field optimization fertilization method mentioned in this application, Figure 2 -A represents the schematic diagram of the dynamic change process of corn straw carbon release rate from 2018 to 2019. Figure 2 -B represents the schematic diagram of the dynamic change process of corn straw carbon release rate from 2019 to 2020; Figure 3 This is a schematic diagram of the dynamic change process of the nitrogen release rate of corn straw in Example 1 of a straw return to field optimization fertilization method mentioned in this application, Figure 3 -A represents the schematic diagram of the dynamic change process of nitrogen release rate of corn straw from 2018 to 2019. Figure 3 -B represents the schematic diagram of the dynamic change process of nitrogen release rate of corn straw from 2019 to 2020; Figure 4 This is a schematic diagram of the dynamic change process of the phosphorus release rate of corn straw in Example 1 of a straw return to field optimization fertilization method mentioned in this application, Figure 4 -A represents the schematic diagram of the dynamic change process of corn straw phosphorus release rate from 2018 to 2019. Figure 4 -B represents the schematic diagram of the dynamic change process of phosphorus release rate of corn straw from 2019 to 2020; Figure 5 This is a schematic diagram of the dynamic change process of the potassium release rate of corn straw in Example 1 of a straw return to field optimization fertilization method mentioned in this application, Figure 5 -A represents the schematic diagram of the dynamic change process of potassium release rate of corn straw from 2018 to 2019. Figure 5 -B represents the schematic diagram of the dynamic change process of potassium release rate of corn straw from 2019 to 2020; Figure 6 This is a schematic diagram of corn yields under different nitrogen application treatments in Example 2 of a straw return to field optimization fertilization method mentioned in this application. Figure 6 -A represents the schematic diagram of corn yield under different nitrogen application treatments in 2017. Figure 6 -B represents the schematic diagram of corn yield under different nitrogen application treatments in 2018. Figure 6 -C represents the schematic diagram of corn yield under different nitrogen application treatments in 2019. Figure 6 -D represents the schematic diagram of corn yield under different nitrogen application treatments in 2020; Figure 7 This is a schematic diagram of corn yields with different amounts of phosphorus fertilizer in Example 3 of a straw return to field optimization fertilization method mentioned in this application, Figure 7 -A is a diagram showing corn yields at different phosphate fertilizer dosages in 2017. Figure 7 -B represents the diagram of corn yield with different amounts of phosphorus fertilizer in 2018. Figure 7 -C represents the diagram of corn yield with different amounts of phosphorus fertilizer in 2019. Figure 7 -D represents the schematic diagram of corn yield with different amounts of phosphorus fertilizer in 2020; Figure 8 This is a schematic diagram of corn yields with different potassium fertilizer dosages in Example 4 of a straw return to field optimization fertilization method mentioned in this application. Figure 8 -A is a diagram showing corn yields at different potassium fertilizer dosages in 2017. Figure 8 -B represents the diagram of corn yield with different potassium fertilizer dosages in 2018. Figure 8 -C represents the diagram of corn yield with different potassium fertilizer dosages in 2019. Figure 8 -D represents the schematic diagram of corn yield with different potassium fertilizer dosages in 2020; Fig. 9 This is a schematic diagram of potassium accumulation in corn with different potassium fertilizer dosages in Example 4 of a straw return to field optimization fertilization method mentioned in this application, Fig. 9 -A is a schematic diagram showing potassium accumulation in corn at different potassium fertilizer dosages in 2017. Fig. 9 -B is a schematic diagram of potassium accumulation in corn with different potassium fertilizer dosages in 2018. Fig. 9 -C represents the schematic diagram of potassium accumulation in corn with different potassium fertilizer dosages in 2019. Fig. 9 -D represents the schematic diagram of potassium accumulation in corn with different potassium fertilizer dosages in 2020; Fig.10 This is a process flow chart of a method for optimizing fertilization by returning straw to fields mentioned in this application. DETAILED DESCRIPTION

[0022] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0023] refer to Fig.10 This application mentions a method for optimizing fertilization by returning straw to fields, comprising: Step S100: Cut the corn stalks into small pieces and air-dry them; cutting them into small pieces increases the contact area between the stalks and the air, soil, and fertilizers in the subsequent processing process, which is conducive to accelerating the subsequent decomposition speed. The air-drying process reduces the moisture content of the stalks, making it easier to store and operate them, while also inhibiting the excessive growth of microorganisms under unsuitable conditions, avoiding unnecessary deterioration or damage of the stalks before returning them to the fields, and creating good conditions for their subsequent return to the fields.

[0024] Step S200: In October to November of the current year, the air-dried corn stalks are spread flat at a depth of 20 to 30 cm in the planting site; The soil temperature and humidity in October and November are conducive to the decomposition and transformation of straw in the soil. Spreading the straw at a depth of 20-30cm can better mix the straw with the soil, contact the microbial community in the soil, accelerate the decomposition process of the straw, and provide a stable environment for the growth of crop roots, avoiding the accumulation of straw on the soil surface that affects sowing or crop growth.

[0025] Step S300: Return the straw to the field using the nylon mesh bag method, put the straw into a 200-300 mesh nylon mesh bag, seal it and lay it flat at a depth of 20-30 cm in the planting field, and separate the bags with soil. The nylon mesh bag can limit the dispersion of the straw, which is convenient for subsequent observation and research on the decomposition of the straw. The mesh bag can be taken out regularly to analyze the decomposition degree of the straw, the release of nutrients, etc., to provide data support for scientific fertilization and field management.

[0026] The 200-300 mesh bags can ensure that the moisture, air and microorganisms in the soil enter the bags and contact with the straw, promote the decomposition of the straw, and prevent the straw fragments from being lost too quickly. The bags are separated by soil, which can make the straw distribution more even, which is conducive to the uniform decomposition of the straw by microorganisms in the soil. At the same time, it ensures the stability of the soil structure and avoids problems such as air permeability and water permeability caused by the concentration of straw in the local soil.

[0027] In this technical solution, when the straw is returned to the field for 1-2 years, the nitrogen application rate is between 188.8-213.9 kg / hm², and when the straw is returned to the field for 3-4 years, the nitrogen application rate is between 163-194.4 kg / hm². The effects of straw on soil nutrients are different at different years of returning to the field. In the early stage of returning straw to the field, such as 1-2 years, the straw decomposes relatively quickly, and a large amount of nitrogen supply is required to meet the demand for nitrogen when microorganisms decompose the straw, ensure the smooth decomposition of the straw, and provide sufficient nutrients for crop growth. As the number of years of returning straw to the field increases, such as after 3-4 years, a certain amount of nitrogen accumulates in the soil. At this time, appropriately reducing the amount of nitrogen application can avoid problems such as waste of resources, environmental pollution, and leggy crops caused by excessive nitrogen fertilizers, while maintaining the balance of soil nutrients and achieving sustainable fertilization management.

[0028] 40% basic fertilizer + 60% topdressing during the jointing stage: The jointing stage is a period of vigorous crop growth and a sharp increase in fertilizer demand. The early basic fertilization ensures the normal growth of the crop seedling stage, and the topdressing of 60% nitrogen fertilizer during the jointing stage can accurately meet the large demand for nitrogen in this critical growth stage of the crop, promote the rapid elongation of the stems, increase the size of the leaves, enhance photosynthesis, increase the biomass accumulation of the crop, and help form a strong plant, providing sufficient material basis for the later booting, flowering and fruiting, and improving the yield and quality of the crop.

[0029] 40% basic fertilization + 40% topdressing + 20% topdressing during flowering: The basic fertilization in the early stage and the topdressing in the middle stage ensure the normal development of the crop's vegetative growth stage, while the topdressing of 20% nitrogen fertilizer during the flowering stage helps promote flower bud differentiation, improve pollen vitality and fertilization rate, and increase fruit setting rate or fruiting rate. Reasonable nitrogen supply can coordinate the balance between crop vegetative growth and reproductive growth, so that crops can smoothly complete the reproductive growth process while ensuring sufficient nutrients, thereby increasing crop yield and fruit quality.

[0030] 40% basic fertilization + 30% topdressing + 15% topdressing during flowering + 15% topdressing during grain filling: The grain filling period is a critical period for crop grains to be full and accumulate dry matter. At this time, topdressing 15% nitrogen fertilizer can promote the transportation and accumulation of photosynthesis products to the grains and increase grain weight. Gradually provide appropriate amounts of nitrogen at different growth stages so that crops can obtain appropriate nutrient support at each growth stage, maximize nitrogen utilization, reduce nitrogen loss, comprehensively promote crop growth and development, and achieve high-yield and high-quality production goals.

[0031] After returning the straw to the field and applying the base fertilizer, collect the surrounding plant residues, crush them and spread them on the soil surface; use a sprayer to spray the fermentation liquid made of brown sugar, yeast and water in a mass ratio of 1:1:(8-10) on the laid plant residues, collect the surrounding plant residues, crush them and spread them on the soil surface, increasing the organic matter cover layer on the soil surface. This layer of cover can effectively reduce soil moisture evaporation, play a role in moisture conservation, maintain soil moisture, and reduce irrigation frequency; it can reduce soil temperature fluctuations and create a relatively stable growth environment for crop roots; it can also inhibit weed growth to a certain extent and reduce weeds from competing with crops for nutrients, water and light.

[0032] In this technical solution, when the straw is returned to the field for 1-2 years, the phosphorus application rate is between 95-107kg / hm², and when the straw is returned to the field for 3-4 years, the phosphorus application rate is between 90-100kg / hm². By adjusting the phosphorus application rate at different return years, it is possible to accurately apply fertilizers according to the actual changes in phosphorus in the soil, improve the utilization efficiency of phosphorus fertilizers, promote the healthy growth of crops, and enhance the stress resistance of crops.

[0033] In this technical solution, when the straw is returned to the field for 1-2 years, the application range of potassium fertilizer is 94.7-110.8kg / hm², and when the straw is returned to the field for 3-4 years, the application range of potassium fertilizer is 78.3-91.4kg / hm. In the early stage of returning to the field, the demand for potassium for crop growth and straw decomposition is high, and applying more potassium fertilizer appropriately helps to meet the demand; as the years of returning to the field increase, the accumulation and supply of potassium in the soil change, and adjusting the application amount of potassium fertilizer can maintain the balance of soil potassium, ensure the normal growth of crops, and improve the yield and quality of crops.

[0034] 1-2 weeks before sowing, the air-dried corn stalks, cellulose decomposing bacteria and nitrogen-fixing bacteria are mixed in a ratio of 100: (0.5-1): (0.3-0.5) by mass percentage to prepare a bacterial solution containing cellulose decomposing bacteria and nitrogen-fixing bacteria, spray the bacterial solution on the corn stalks, cover the treated corn stalks with plastic film, and compost and ferment for 7-10 days at 25-30°C. A specific ratio of cellulose decomposing bacteria can quickly and efficiently decompose the cellulose in the corn stalks, convert it into small molecular sugars and other substances, accelerate the decomposition process of the stalks, and shorten the time for the stalks to decompose naturally in the soil. Nitrogen-fixing bacteria can fix nitrogen in the air, increase the nitrogen content in the composting process, provide sufficient nitrogen sources for the growth of microorganisms and the decomposition of the stalks, and at the same time increase the nitrogen content of the stalk fermentation products, thereby enhancing the effect of improving soil fertility after returning to the field.

[0035] After spraying on the soil surface, shallow tillage is carried out, and the tillage depth is controlled at 5-10cm. Plastic film covering creates a relatively closed, warm and humid environment. The temperature range of 25-30℃ is the suitable temperature for the growth and reproduction of these microorganisms, which is conducive to the large-scale reproduction and active metabolism of microorganisms, accelerates the fermentation speed and improves the fermentation effect. After 7-10 days of composting and fermentation, the straw is partially decomposed, the texture becomes looser, and the nutrients are easier to be absorbed and utilized by soil microorganisms and crops. After returning to the field, it can release nutrients faster, improve soil structure, and increase soil fertility.

[0036] The technical solution of the present application will be further described below by way of embodiments in combination with the accompanying drawings.

[0037] The test soil was collected from Dafangshen Village, Chaoyangpo Town, Gongzhuling City, Jilin Province, and the soil type was black soil. Soil samples were collected after corn harvest in 2018, with a sampling depth of 0-20cm. The collected soil was air-dried, and the stones and corn roots were removed. The basic physical and chemical properties of the test soil were as follows: pH value was 5.23, organic matter was 34.15g / kg, total nitrogen was 1.92g / kg, total phosphorus was 0.54g / kg, available phosphorus was 6.68mg / kg, total potassium was 21.73g / kg, and available potassium was 86.14mg / kg.

[0038] The test straw was collected from corn harvest in 2018. The collected straw was cut into 5-8 cm, air-dried, and stored for later use. The nutrient mass fractions of the test straw were measured before the experiment: corn straw C: 36.74%, N: 0.763%, P: 0.12%, K: 1.17%; C / N ratio: 48.2:1.

[0039] Experimental method: The nylon mesh bag method was used to simulate the corn planting pattern and study the decomposition and potassium release of corn straw. The cultivation experiment was carried out at the Dafangshen Village Experimental Base in Chaoyangpo, Gongzhuling. 40g of straw was selected according to the area of ​​the nylon mesh bag, and the amount of straw was converted according to the straw yield per unit area in 2018. It was put into a 20×20cm 200-mesh nylon mesh bag, sealed, and laid flat at 25cm in the experimental site, with each nylon mesh bag separated by soil. After completing the straw return to the field and applying base fertilizer, the surrounding plant residues were collected, crushed and sprinkled on the soil surface; the fermentation liquid prepared by brown sugar, yeast and water in a mass ratio of 1:1:9 was sprayed on the laid plant residues with a sprayer. According to the deep plowing and returning of straw to the field method in Northeast China, the simulated cultivation time was from October 2018 to October 2019, a total of 360 days.

[0040] Determination items and methods: After the bagged straw is returned to the field, a sample is taken every 30 days, and 3 bags are taken each time for 3 repetitions, and a total of 15 samples are taken during the corn growth period. After sampling, the samples are washed and placed in an oven to dry at 70°C to constant weight. The total carbon content of the straw is determined by the potassium dichromate volumetric method-external heating method; the total nitrogen content is determined by the fully automatic Kjeldahl nitrogen analyzer (FOSS) after the straw is digested with concentrated sulfuric acid-hydrogen peroxide; the total phosphorus content is determined by the molybdenum antimony colorimetric method; and the total potassium content is determined by the flame photometer method.

[0041] Results and analysis; (1) Corn straw decomposition rate; The dynamic changes of corn straw decomposition process Figure 1 As shown, Figure 1 -A represents the schematic diagram of the dynamic changes in corn straw decomposition from 2018 to 2019. Figure 1 -B represents a schematic diagram of the dynamic changes in corn straw decomposition between 2019 and 2020. The test straw decomposed slowly between 0 and 180 days (freezing period) in the early stage of cultivation, with decomposition rates of 9.5% (2018-2019) and 12.6% (2019-2020), respectively. Starting from 180 days, the decomposition process of the straw was mainly divided into three periods: rapid decomposition period, decomposition slowdown period, and decomposition stagnation period. The 180th to 300th day was a rapid decomposition period, with an average decomposition rate of 0.26 g / d (2018-2019) and 0.23 g / d (2019-2020), 300th to 330th day was a decomposition slowdown period, with an average decomposition rate of 0.04 g / day (2018-2019) and 0.08 g / day (2019-2020), and 330th to 360th day was a decomposition stagnation period, with an average decomposition rate of 0.01 g / day (2018-2019) and 0.02 g / day (2019-2020). The final decomposition rates of the year were 91.4% (2018-2019) and 92.7% (2019-2020).

[0042] (2) Corn straw carbon release rate; The dynamic change process of corn straw carbon release rate is as follows Figure 2 shown. Figure 2 -A represents the schematic diagram of the dynamic change process of corn straw carbon release rate from 2018 to 2019. Figure 2 -B is a schematic diagram of the dynamic changes in the carbon release rate of corn straw between 2019 and 2020; the carbon release of the test straw was slow between 0 and 180 days (freezing period) in the early stage of cultivation, with carbon release rates of 13.5% (2018-2019) and 16.2% (2019-2020), respectively. Starting from 180 days, the carbon release of the straw was mainly divided into three periods: rapid release period, release slowdown period, and release stagnation period. The 180th to 270th day was a rapid release period, with an average carbon release rate of 0.27g / d (2018-2019) and 0.20g / d (2019-2020), 270th to 300th day was a slow-release period, with an average release rate of 0.07g / day (2018-2019) and 0.10g / day (2019-2020), and 300th to 360th day was a stagnant release period, with an average release rate of 0.01g / day. The final carbon release rates of the year were 80.2% (2018-2019) and 81.4% (2019-2020).

[0043] (3) Nitrogen release rate of corn straw; The dynamic change process of nitrogen release rate of corn straw is as follows Figure 3 As shown, Figure 3 -A represents the schematic diagram of the dynamic change process of nitrogen release rate of corn straw from 2018 to 2019. Figure 3 -B represents a schematic diagram of the dynamic changes in the nitrogen release rate of corn straw between 2019 and 2020. The nitrogen release rate of the test straw was slow during the early stage of cultivation (0-180 days) (freezing period), and the nitrogen release rates were 21.3% (2018-2019) and 18.8% (2019-2020). Starting from 180 days, the nitrogen release process of the straw was mainly divided into three periods: rapid release period, release slowdown period, and release stagnation period. The 180th to 240th day was a rapid release period, with an average nitrogen release rate of 0.33g / d (2018-2019) and 0.34g / d (2019-2020), the 240th to 270th day was a decomposition slowdown period, with an average release rate of 0.06g / day (2018-2019) and 0.05g / day (2019-2020), and the 270th to 360th day was a decomposition stagnation period, with an average decomposition rate of 0.01g / day. The final nitrogen release rates of the year were 78.2% (2018-2019) and 74.5% (2019-2020).

[0044] (4) Phosphorus release rate of corn straw; The dynamic change process of phosphorus release rate of corn straw Figure 4 As shown, Figure 4 -A represents the schematic diagram of the dynamic change process of corn straw phosphorus release rate from 2018 to 2019. Figure 4 -B is a schematic diagram of the dynamic changes in the phosphorus release rate of corn straw between 2019 and 2020. The phosphorus release rate of the test straw was slow during the early stage of cultivation (0-180 days) (freezing period), and the phosphorus release rates were 18.5% (2018-2019) and 23.6% (2019-2020). Starting from 180 days, the phosphorus release process of the straw was mainly divided into three periods: rapid release period, release slowdown period, and release stagnation period. The 180th to 240th day was a rapid release period, with an average phosphorus release rate of 0.39 g / d (2018-2019) and 0.38 g / d (2019-2020), the 240th to 270th day was a decomposition slowdown period, with an average release rate of 0.05 g / day (2018-2019) and 0.06 g / day (2019-2020), and the 270th to 360th day was a decomposition stagnation period, with an average decomposition rate of 0.02 g / day. The final phosphorus release rates of the year were 85.1% (2018-2019) and 88.4% (2019-2020).

[0045] (5) Potassium release rate of corn straw; The dynamic change process of potassium release rate of corn straw is as follows Figure 5 As shown, Figure 5 -A represents the schematic diagram of the dynamic change process of potassium release rate of corn straw from 2018 to 2019. Figure 5 -B represents the schematic diagram of the dynamic change process of potassium release rate of corn straw from 2019 to 2020. The potassium release of the test straw was slow between 0-180 days (freezing period) in the early stage of cultivation, and the potassium release rate was 14.9% (2018-2019) and 23.6% (2019-2020), respectively. From 180 days on, the potassium process of the straw was mainly divided into two periods: rapid release period and release stagnation period. Among them, the 180th to 240th day was the rapid release period, with an average potassium release rate of 0.52g / d (2018-2019) and 0.49g / d (2019-2020), and 240th to 365th day was the release stagnation period, with an average release rate of 0.01g / day. The final potassium release rates in the year were 96.3% (2018-2019) and 97.1% (2019-2020).

[0046] Based on the decomposition rate of corn straw and the release rates of carbon, nitrogen, phosphorus and potassium, it can be seen that returning straw to the field plays an important role in providing carbon, nitrogen, phosphorus and potassium sources for the soil. In the cultivation experiment of the year, the final carbon release rate reached 80.2% in 2018-2019 and 81.4% in 2019-2020. Returning straw to the field can return a large amount of carbon to the soil in a natural and environmentally friendly way, partially replacing the need to supplement soil carbon sources through chemical synthesis, and reducing the environmental pressure caused by the production of inputs such as chemical fertilizers. The gradual release of carbon after returning straw to the field helps to maintain the carbon cycle balance of farmland ecosystems. In the soil, the carbon released during the decomposition of straw can be used by soil microorganisms, and the activities of microorganisms can further improve the soil structure and function, forming a benign ecological cycle. In contrast, the use of chemical fertilizers often breaks this natural carbon cycle balance. Excessive chemical nutrient input may lead to changes in the structure of soil microbial communities and reduce the stability of soil ecosystems. Returning straw to the fields makes the soil ecosystem healthier and more stable through the natural carbon release process, reduces damage to the environment, and reflects its green and environmentally friendly characteristics.

[0047] With the continuous release of straw carbon, the carbon content in the soil increases and the soil fertility is improved to a certain extent. This reduces the reliance on chemical fertilizers in agricultural production. Since straw slowly releases carbon and other nutrients in the soil, it can meet the demand for some nutrients for corn growth to a certain extent, and farmers can reduce the purchase of chemical fertilizers accordingly. Taking nitrogen fertilizer as an example, after understanding the release rules of nitrogen and carbon in straw, precise fertilization is carried out according to crop needs, avoiding excessive application of nitrogen fertilizers, thereby saving fertilizer costs. In the long run, it saves farmers a considerable amount of expenses.

[0048] The method of optimizing fertilization based on returning straw to the field mentioned in this application can also help improve soil structure and increase the soil's ability to retain water and fertilizer. Good soil structure can reduce the risk of soil erosion and compaction, and reduce the cost of soil improvement required due to deterioration in soil quality. In traditional agriculture, excessive reliance on chemical fertilizers may lead to soil compaction, requiring additional manpower and material resources for soil improvement. Returning straw to the field improves the soil in a natural way, reducing this part of potential cost expenditures.

[0049] The dynamic change process of corn straw carbon release, from slow release in the early stage to changes in different stages in the later stage, provides a relatively stable nutrient supply process for corn growth. In the early stage of corn growth, although the carbon release of corn straw is slow, the demand for nutrients of corn is relatively small at this time; as corn enters the rapid growth period, the carbon release of corn straw also enters a rapid period. For example, in 2018-2019, the 180th to 270th day was a rapid release period, and the average carbon release rate reached 0.27g / d, which can meet the large demand for nutrients for the rapid growth of corn.

[0050] Example 2: Experiment on nitrogen fertilizer dosage under the condition of returning straw to the field.

[0051] Materials and methods; Experimental design: The experiment was a positioning experiment (starting date: 2017) with a two-factor design. The main treatments were straw return to the field (all corn straw was crushed in the field, deep plowing and buried in the field) and straw removal from the field (all corn straw was removed from the field after harvest and deep plowing). The secondary treatments were 6 nitrogen application rates, namely 0 (denoted as N0), 70 (denoted as N 70 )、140(denoted as N 140 )、210(denoted as N 210 )、280(denoted as N 280 ) and 350 (denoted as N 350 )kg / hm 2 There were 12 treatments in total, and the amount of phosphorus and potassium fertilizers in each treatment was the same, both at 90 kg / hm 2 The fertilization method was to apply 40% nitrogen fertilizer and all phosphorus and potassium fertilizers as basal fertilizer before sowing, and 60% nitrogen fertilizer was applied as topdressing at the jointing stage. The tested corn variety was Fumin 985, and the planting density was 70,000 plants / hm2. 2 The sowing dates were May 4 (2017), May 14 (2018), May 9 (2019) and April 30 (2020), and the harvest periods were September 30 (2017), October 7 (2018), October 4 (2019) and October 6 (2020). The plot area was 40m 2 , repeated 3 times, and the plots were arranged randomly.

[0052] Sample collection and determination: After the corn harvest in 2016, basic soil samples were collected. The entire experimental field was used as the sampling unit, and 30 points were evenly distributed. The 0-120cm tillage layer soil was taken, weeds and gravel were picked out, and mixed samples were made according to the "four-part method" and brought back to the laboratory for air drying and preservation. After each season of corn harvest, the tillage layer soil of each plot was collected and processed in the same way as above. The inorganic nitrogen content of the soil was determined for each 20cm layer.

[0053] At the maturity stage of corn each season, six representative plants were selected from each plot, decomposed into stalks and kernels, withered at 105°C for 30 min, dried at 80°C to constant weight, weighed and crushed after dry weight, digested with concentrated H2SO4-H2O2, and the nitrogen content was determined by Kjeldahl method.

[0054] During the corn harvest period, the middle two rows in each plot were harvested and the number of ears in each plot was measured. After harvest, the corn was naturally dried in the drying yard. When the moisture content of the grains was ≤20%, they were manually threshed and the moisture content of the grains was measured with a PM-8188 grain moisture meter. The yield was calculated based on the standard moisture content of 14% and converted into yield per unit area according to the measured yield area.

[0055] Results and analysis; Regarding the corn yield treated with straw return and different nitrogen fertilizer dosages, refer to Figure 6 ,in, Figure 6 -A represents the schematic diagram of corn yield under different nitrogen application treatments in 2017. Figure 6 -B represents the schematic diagram of corn yield under different nitrogen application treatments in 2018. Figure 6 -C represents the schematic diagram of corn yield under different nitrogen application treatments in 2019. Figure 6 -D represents the schematic diagram of corn yield under different nitrogen fertilizer treatments in 2020. Fertilization treatment significantly affects spring corn yield. Compared with the treatment without nitrogen fertilizer (N0), nitrogen fertilizer treatment under the conditions of straw return to the field and straw leaving the field had a significant yield-increasing effect ( P <0.05), among which the increases under the straw return condition were 13.9%-55.9% (2017), 17.1%-42.8% (2018), 28.4%-75.7% (2019) and 75.3%-155.0% (2020), respectively; the increases under the straw removal condition were 6.5%-36.6% (2017), 16.4%-47.0% (2018), 76.5%-190.3% (2019) and 106.5%-258.2% (2020), respectively. In different nitrogen application treatments, corn yield increased with nitrogen application of 70-210 kg / hm 2 The range of nitrogen application increases with the increase of nitrogen application rate. When the nitrogen application rate exceeds this range, corn yield no longer increases or shows a downward trend. 70 、N 140 ) The corn yield was lower than that of the straw-off-field treatment. When the nitrogen application rate increased to 210 kg / hm 2 After that, the corn yield of the straw return treatment was slightly higher than that of the straw off-field treatment. From 2018 to 2020, the corn yield of the straw return treatment was higher than that of the straw off-field treatment. In 2019 and 2020, the N0 and N 70 and N 140 treatment was significantly higher than the straw-off-field treatment ( P <0.05), Figure 6 In the data, ns and * respectively indicate that there is no significant difference and significant difference at the 0.05 level between the treatments of returning straw to the field and removing straw from the field under the same nitrogen application rate; different lowercase letters respectively indicate that there is significant difference at the 0.05 level between different fertilization treatments under the conditions of returning straw to the field and removing straw from the field.

[0056] The nitrogen application rate required for the highest corn yield under the condition of straw leaving the field is 209.7 kg / hm 2、204.9kg / hm 2 、203.5kg / hm 2 and 200.1kg / hm 2 Compared with the straw-off-field treatment, the nitrogen application amount required for the maximum corn yield in 2017, 2018, 2019 and 2020 decreased in the straw-returned-to-field treatment, and the decline increased with the extension of the straw-returned-to-field period, with the decline rates being 2.9%, 3.5%, 9.0% and 14.3%, respectively. Taking 95% of the theoretical maximum yield nitrogen fertilizer dosage as the confidence interval, it was calculated that in the early stage of straw-returned-to-field (1-2 years), straw nitrogen can replace 2.9%-3.5% of chemical nitrogen fertilizer, and the appropriate dosage is 188.8-213.9 kg / hm 2 After 3-4 years of straw return, nitrogen from straw can replace 9.0%-14.3% of nitrogen fertilizer, and the appropriate nitrogen application rate is 163-194.4 kg / hm2. 2 between.

[0057] Regarding the nitrogen fertilizer utilization efficiency of corn treated with straw return and different nitrogen fertilizer application rates, fertilization treatment significantly affected the nitrogen absorption and utilization rate, agronomic utilization rate and partial productivity of spring corn. Under different nitrogen application conditions, except for 2017, the nitrogen absorption and utilization rate, agronomic utilization rate and partial productivity of corn showed a downward trend with the increase of nitrogen application rate. Under the same nitrogen fertilizer application rate, except for 2017, the nitrogen absorption and utilization rate, agronomic utilization rate and partial productivity of the straw return treatment in other years were higher than those of the straw removal treatment. The cumulative increase in the four years was 3.8%-21.7%, 4.7%-65.7% and 1.9%-9.6%, respectively, among which N 70 and N 140 There were significant differences in the nitrogen agronomic utilization efficiency among the treatments ( P <0.05).

[0058] Regarding the changes in soil inorganic nitrogen content after returning straw to the field and different nitrogen fertilizer application rates: the inorganic nitrogen content of the soil in the 0-20cm tillage layer is the highest, and with the increase in soil depth, the inorganic nitrogen content of the soil in the 0-120cm layer shows a downward trend; compared with the treatment without nitrogen fertilizer, nitrogen application significantly increased the inorganic nitrogen content of the soil in the 0-120cm layer. In the different nitrogen application treatments, the inorganic nitrogen content of the soil in the 0-120cm layer increased significantly with the increase in nitrogen application rate. Under the same nitrogen application rate, compared with the straw removal treatment, the straw return treatment increased the inorganic nitrogen content of the soil in the 0-20cm and 20-40cm layers, with increases of 6.5%-35.5% and 5.3%-30.2%, respectively. At the same time, the inorganic nitrogen content of the soil in the 40-120cm layer was reduced.

[0059] Effects of straw return and nitrogen application level on nitrogen balance of maize. The significant results showed that, except for the crop carry-out, fertilization and straw treatments significantly or extremely significantly affected the residual inorganic nitrogen and the apparent nitrogen loss, and there was a significant interaction between the two. 2 The range increased significantly when the nitrogen application rate increased to 280 kg / hm 2 After the crop was fertilized, the amount of nitrogen carried out by the crop showed a downward trend, while the residual inorganic nitrogen and the apparent nitrogen loss increased significantly with the increase of nitrogen application rate. It can be seen that excessive nitrogen application not only cannot significantly increase the nitrogen absorption of corn, but also significantly increases the residual and loss of inorganic nitrogen in the soil profile. 70 Processing and N 140 Although the residual inorganic nitrogen and apparent loss were low in the treatment, the nitrogen supply was insufficient, so the nitrogen carried out by the crop was greater than the nitrogen application rate, resulting in the residual inorganic nitrogen being significantly lower than the initial inorganic nitrogen. 210 Since the crop nitrogen outflow and total nitrogen input were similar, the residual inorganic nitrogen was similar to the initial inorganic nitrogen. In addition, under the same nitrogen application rate, the apparent nitrogen loss of the straw return treatment was significantly lower than that of the straw removal treatment ( P <0.05), with a decrease of 26.0%-87.0%.

[0060] Under the conditions of returning straw to the field and leaving straw from the field, nitrogen fertilizer application could significantly increase corn yield. When the nitrogen application rate was increased to 210 kg / hm 2 , the grain yield is the highest, and increasing the amount of nitrogen fertilizer will not increase or even reduce the corn yield to a certain extent. Under the same nitrogen fertilizer application level, the corn yield of the straw return treatment is slightly higher than that of the straw removal treatment; according to the linear plus platform regression equation, the nitrogen fertilizer application amount for the highest yield of straw return in the four years is 203.7kg / hm 2 、197.7kg / hm 2 、185.1kg / hm 2 and 171.5kg / hm 2 Compared with leaving the straw in the field, returning the straw to the field can reduce the amount of nitrogen fertilizer used, and the reduction rate increases with the extension of the returning period, with the four-year reduction rate being 2.9%, 3.5%, 9.0% and 14.3% respectively. Under the same nitrogen application rate, returning the straw to the field can increase the inorganic nitrogen content of the soil in the tillage layer and sub-tillage layer (0-40cm) while reducing the inorganic nitrogen content in the deep soil (40-120cm). The results of soil nitrogen budget balance show that under the conditions of returning the straw to the field and leaving the field, the annual nitrogen application rate of 210kg / hm 2 , the soil nitrogen balance showed a surplus state, and the apparent nitrogen loss rate of straw leaving the field was significantly higher than that of straw returning to the field.

[0061] In summary, in the early stage of straw return (1-2 years), straw nitrogen can replace chemical nitrogen fertilizer by 2.9%-3.5%, and the appropriate dosage is 188.8-213.9 kg / hm2. 2 After 3-4 years of straw return, nitrogen from straw can replace 9.0%-14.3% of nitrogen fertilizer, and the appropriate nitrogen application rate is 163kg / hm 2 -194.4kg / hm 2 between.

[0062] From the perspective of the effect of fertilization treatment, the effect of fertilization on spring corn yield is very significant. Compared with the N0 treatment without nitrogen fertilizer, the nitrogen treatment under both straw return and straw removal conditions brought significant yield increases. During 2017-2020, under the condition of straw return, the increase in yield was between 13.9% and 155.0%. This shows that through reasonable fertilization, corn yield can be greatly improved under the condition of straw return. Similarly, under the condition of straw removal, the increase in yield during the same period was between 6.5% and 258.2%, which also fully illustrates the positive effect of fertilization on yield. The effect of different nitrogen application rates on yield is also worthy of attention. When the nitrogen application rate is in the range of 70-210kg / hm², corn yield will increase with the increase in nitrogen application rate. This shows that in this range, increasing nitrogen fertilizer input can provide sufficient nutrients for corn growth and promote yield increase. Comparing the treatment of returning straw to the field and leaving the field with straw, the corn yield of the treatment of returning straw to the field was higher than that of the treatment of leaving the field with straw during 2018-2020. Especially in 2019 and 2020, some treatments showed significant differences, which directly reflected the advantages of returning straw to the field in increasing corn yield. In addition, in the treatment of returning straw to the field, the amount of nitrogen required for the maximum corn yield decreased with the extension of the years. This shows that as the years of returning straw to the field increase, the soil's own fertility is improved, and the dependence on chemical nitrogen fertilizers is reduced, but the corn yield can still be guaranteed.

[0063] Example 3: Test on the suitable amount of phosphate fertilizer under the condition of returning straw to the field.

[0064] The experiment adopted a two-factor design. The main plot was straw return to the field (all corn straw in the field was crushed, deep plowed and buried in the field) and straw removal from the field (all corn straw was removed from the plot after corn harvest and deep plowed). The sub-plot was 6 phosphorus application levels, namely 0 (denoted as P0), 30 (denoted as P 30 ), 60 (denoted as P 60 ), 90 (denoted as P 90 ), 120 (denoted as P 120 ) and 150 (denoted as P 150 )kg / hm 2 There were 12 treatments in total, and the amount of nitrogen fertilizer and potassium fertilizer in each treatment was the same, 210 kg / hm 2 and 90kg / hm 2The fertilization method is to apply 30% nitrogen fertilizer and all phosphorus and potassium fertilizers as basal fertilizer before sowing, and 70% nitrogen fertilizer is applied as topdressing at the jointing stage. The tested corn variety is Fumin 985, and the planting density is 70,000 plants / hm2. 2 The sowing dates were May 4 (2017), May 14 (2018), May 9 (2019) and April 30 (2020), and the harvest periods were September 30 (2017), October 7 (2018), October 4 (2019) and October 6 (2020). The plot area was 40m 2 , repeated 3 times, and the plots were arranged randomly.

[0065] After the corn harvest in 2016, basic soil samples were collected. The entire experimental field was used as the sampling unit, and 30 points were evenly distributed. The 0-120cm tillage layer soil was taken, weeds and gravel were picked out, and mixed samples were made according to the "four-part method" and brought back to the laboratory for air drying and preservation. After each season of corn harvest, the tillage layer soil of each plot was collected and processed in the same way as above. Each 20cm layer was used to measure the soil available phosphorus and total phosphorus content.

[0066] At the maturity stage of corn each season, six representative plants were selected from each plot, decomposed into stalks and kernels, withered at 105°C for 30 min, dried at 80°C to constant weight, weighed and crushed after dry weight, digested with concentrated H2SO4-H2O2, and the phosphorus content of the plants was determined by the molybdenum antimony colorimetric method.

[0067] During the corn harvest period, the middle two rows in each plot were harvested and the number of ears in each plot was measured. After harvest, the corn was naturally dried in the drying yard. When the moisture content of the grains was ≤20%, they were manually threshed and the moisture content of the grains was measured with a PM-8188 grain moisture meter. The yield was calculated based on the standard moisture content of 14% and converted into yield per unit area according to the measured yield area.

[0068] Regarding the treatment of corn yield with straw return and different phosphate fertilizer application rates, refer to Figure 7 , Figure 7 -A is a diagram showing corn yields at different phosphate fertilizer dosages in 2017. Figure 7 -B represents the diagram of corn yield with different amounts of phosphorus fertilizer in 2018. Figure 7 -C represents the diagram of corn yield with different amounts of phosphorus fertilizer in 2019. Figure 7 -D represents the schematic diagram of corn yield with different phosphorus fertilizer application in 2020. Fertilization treatment significantly affects spring corn yield. Compared with the treatment without phosphorus fertilizer (P0), phosphorus application under the conditions of straw return to the field and straw leaving the field had a significant yield-increasing effect ( P<0.05), among which the increases under the straw return condition were 6.9%-20.4% (2017), 9.7%-20.5% (2018), 6.6%-19.4% (2019) and 5.7%-12.3% (2020), respectively; the increases under the straw removal condition were 8.2%-22.8% (2017), 9.3%-19.9% ​​(2018), 8.4%-21.8% (2019) and 2.3%-14.1% (2020), respectively. In different phosphorus application treatments, corn yield increased at phosphorus application rates of 30-90 kg / hm 2 The corn yield increased with the increase of phosphorus application within this range. When the phosphorus application exceeded this range, the corn yield showed a downward trend. Compared with the straw-off-field treatment, under the same amount of phosphorus fertilizer, except for 2017, the corn yield of the straw-on-field treatment was slightly higher than that of the straw-off-field treatment, with the increase of 1.6%-5.6% (2018), 1.9%-4.1% (2019) and 0.5%-6.3% (2020). Figure 7 In the data, ns and * respectively indicate that there is no significant difference and significant difference at the 0.05 level between the treatments of returning straw to the field and removing straw from the field under the same nitrogen application rate; different lowercase letters respectively indicate that there is significant difference at the 0.05 level between different fertilization treatments under the conditions of returning straw to the field and removing straw from the field.

[0069] The phosphorus application rate required for the highest corn yield under the straw return condition in 2017, 2018, 2019 and 2020 was 102.1 kg / hm 2 、99.8kg / hm 2 、95.3kg / hm 2 and 94.1kg / hm 2 , the phosphorus application rate required for the highest corn yield under the condition of straw leaving the field is 109.8kg / hm 2 、106.7kg / hm 2 、106.6kg / hm 2 and 108.7kg / hm 2 Compared with the straw-off-field treatment, the phosphorus application amount required for the highest corn yield in 2017, 2018 and 2019 decreased in the straw-return-to-field treatment, with a decrease of 7.0%, 6.5%, 10.6% and 13.4% respectively. Taking 95% of the theoretical maximum yield phosphorus fertilizer application amount as the confidence interval, it was calculated that under the condition of returning straw to the field for 1-2 years, the appropriate amount of phosphorus fertilizer is 95-107 kg / hm 2 Under the condition of returning straw to the field for 3-4 years, the appropriate phosphorus application rate is 90-100 kg / hm 2 between.

[0070] Fertilization treatment significantly affected the phosphorus absorption and utilization rate, agronomic utilization rate and partial productivity of spring maize. Under different phosphorus application conditions, the phosphorus absorption and utilization rate, agronomic utilization rate and partial productivity of maize all showed a downward trend with the increase of phosphorus application. Under the same phosphorus fertilizer application rate, the phosphorus absorption and utilization rate, agronomic utilization rate and partial productivity of the straw return treatment were higher than those of the straw removal treatment, and the increase range was 5.1%-29.1%, 5.3%-28.7% and 0.8%-3.5%, respectively. Among them, P 30 and P 60 The differences in phosphorus absorption and utilization rates and agronomic utilization rates among the treatments were significant ( P <0.05).

[0071] Regarding the changes in soil available phosphorus content during the maize maturity period after returning straw to the field and different phosphorus application treatments, except for 2017, the amount of phosphorus fertilizer used had a significant effect on soil available phosphorus content, but had no significant effect on soil total phosphorus content. In the same year, soil available phosphorus content increased with the increase in phosphorus fertilizer application. Under the same amount of phosphorus fertilizer, the soil available phosphorus content in the straw return treatment was higher than that in the straw removal treatment, but the difference did not reach a significant level ( P >0.05); while there was no significant difference in total phosphorus content. Compared with the beginning of the experiment, the performance was the same under straw return and straw removal, P0, P 30 and P 60 The effective phosphorus content of the treatment decreased, and the amount of phosphorus fertilizer increased to 90kg / hm 2 , the available phosphorus content in soil was close to the initial value; while the total phosphorus content in different phosphorus application treatments was close to that at the beginning of the experiment.

[0072] The apparent balance results of straw return and different phosphorus application treatments showed that, except for the crop carry-out, fertilization and straw treatments significantly or extremely significantly affected the apparent profit and loss, balance coefficient and actual balance rate, and there was a significant interaction between the two. The crop carry-out performance of straw return and straw removal treatments was consistent, increasing with the increase of phosphorus application within the range of 0-90cm. When the phosphorus application rate increased to 120kg / hm 2 , the amount of crop carried out showed a downward trend. In the soil phosphorus surplus and deficit, the phosphorus deficit decreased with the increase of phosphorus application, among which the phosphorus application rate of straw return treatment was 30-60kg / hm 2 Within this range, soil phosphorus is in a state of deficiency. When the phosphorus application rate is increased to 90 kg / hm 2 After the straw is removed from the field, phosphorus is in a state of abundance; while the straw treatment is 30-90 kg / hm 2 Within this range, soil phosphorus is in a state of deficiency. When the phosphorus application rate is increased to 120 kg / hm 2 , the soil phosphorus is in a sufficient state.

[0073] The results of Example 3 show that compared with the treatment without phosphate fertilizer (P0), the phosphate treatment under the conditions of returning straw to the field and leaving the field with straw both brought about significant yield-increasing effects. During the period 2017-2020, the yield increase under the condition of returning straw to the field was 5.7%-20.4%, and the yield increase under the condition of leaving the field with straw was 2.3%-22.8%. This shows that the application of phosphate fertilizer can effectively increase corn yield. In terms of the effect of different phosphorus application rates on yield, corn yield increases with the increase in phosphorus application within the range of 30-90kg / hm², and when the phosphorus application rate exceeds this range, the yield shows a downward trend. The fertilization strategy involved in this application can achieve a good level of corn yield by accurately controlling the amount of phosphorus applied, providing a scientific basis for increasing yield.

[0074] Comparing the treatment of returning straw to the field and leaving straw off the field, under the same amount of phosphorus fertilizer, except for 2017, the corn yield of returning straw to the field was slightly higher than that of leaving straw off the field, and the increase was 0.5%-6.3% from 2018 to 2020. From the perspective of the amount of phosphorus required for the maximum corn yield in different years, the amount of phosphorus required for the maximum corn yield under the condition of returning straw to the field was lower than that of leaving straw off the field, and the decrease was 6.5%-13.4% from 2017 to 2020. Taking 95% of the theoretical maximum yield phosphorus fertilizer dosage as the confidence interval, it is concluded that the appropriate amount of phosphorus fertilizer for returning straw to the field for 1-2 years is between 95-107kg / hm², and between 90-100kg / hm² for 3-4 years. This application can achieve an increase in corn yield through returning straw to the field and reasonable planning of phosphorus fertilizer dosage.

[0075] The experiment was a positioning experiment with a start and end date of 2017-2020. A two-factor design was used. The main treatments were straw return to the field (all corn straw in the field was crushed, deep plowing and buried in the field) and straw removal from the field (all corn straw was removed from the plot after corn harvest and deep plowing). The secondary treatments were 6 potassium fertilizer application rates, namely 0 (denoted as K0), 30 (denoted as K 30 ), 60 (denoted as K 60 ), 90 (denoted as K 90 ), 120 (denoted as K 120 ) and 150 (denoted as K 150 )kg / hm 2 There were 12 treatments in total, and the amount of nitrogen and phosphorus fertilizers in each treatment was the same, 210 kg / hm 2 and 90kg / hm 2 The fertilization method is to apply 30% nitrogen fertilizer and all phosphorus and potassium fertilizers as basal fertilizer before sowing, and 70% nitrogen fertilizer is applied as topdressing at the jointing stage. The tested corn variety is Fumin 985, and the planting density is 70,000 plants / hm2. 2The sowing dates were May 4 (2017), May 14 (2018), May 9 (2019) and April 30 (2020), and the harvest periods were September 30 (2017), October 7 (2018), October 4 (2019) and October 6 (2020). The plot area was 40m 2 , repeated 3 times, and the plots were arranged randomly.

[0076] After the corn harvest in 2016, basic soil samples were collected. The whole experimental field was used as the sampling unit, and 30 points were evenly distributed. The 0-20 cm tillage layer soil was taken, weeds and gravel were picked out, and mixed samples were made according to the "four-part method" and brought back to the laboratory for air drying and preservation. After each season of corn harvest, the tillage layer soil of each plot was collected and processed in the same way as above. The method of Bao Shidan was used to determine the soil available potassium, slow-release potassium and total potassium. After air drying, it was ground with a mallet. 5g of soil sample that passed through a 1mm sieve was taken, and 1mol / L ammonium acetate solution (soil-liquid ratio 1:10) was added for extraction. After shaking for 30 minutes, it was filtered and the soil available potassium content was determined by a flame photometer; 5g of soil sample that passed through a 1mm sieve was taken, and 2mol / L nitric acid solution (soil-liquid ratio 1:4) was added for extraction. The slow-release potassium content was equal to the potassium extracted by nitric acid minus the potassium extracted by ammonium acetate. Take 5g of soil sample passed through a 0.25mm sieve and 2.50g of sodium hydroxide and put them into a nickel-orange pot. Melt them completely at 700℃ and determine the total potassium content with a flame photometer.

[0077] At the maturity stage of corn each season, six representative plants were selected from each plot, decomposed into stalks and kernels, withered at 105°C for 30 min, dried at 80°C to constant weight, weighed and crushed after dry weight, digested with concentrated H2SO4-H2O2, and the potassium content was determined by flame photometry.

[0078] During the corn harvest period, the middle two rows in each plot were harvested and the number of ears in each plot was measured. After harvest, the corn was naturally dried in the drying yard. When the moisture content of the grains was ≤20%, they were manually threshed and the moisture content of the grains was measured with a PM-8188 grain moisture meter. The yield was calculated based on the standard moisture content of 14% and converted into yield per unit area according to the measured yield area.

[0079] Results and analysis; Regarding the treatment of corn yield with straw return and different potassium fertilizer dosages, refer to Figure 8 , Figure 8 -A is a diagram showing corn yields at different potassium fertilizer dosages in 2017. Figure 8 -B represents the diagram of corn yield with different potassium fertilizer dosages in 2018. Figure 8 -C represents the diagram of corn yield with different potassium fertilizer dosages in 2019. Figure 8-D represents the schematic diagram of corn yield with different potassium fertilizer application in 2020. Potassium application treatment significantly affects corn yield, while straw treatment has a significant effect on corn yield in 2020, and the interaction between the two factors reached a significant level in 2020. In the same year, compared with different potassium fertilizer treatments (K0), straw return to the field and potassium application without straw in the field both have a significant yield-increasing effect ( P <0.05), among which the increases under the condition of returning straw to the field were 9.0%-17.0% (2017), 6.0%-15.2% (2018), 7.7%-10.9% (2019) and 8.2%-11.7% (2020), with an average increase of 7.8%-13.7% over the four years; the increases under the condition of leaving the straw from the field were 7.8%-19.5% (2017), 8.1%-18.1% (2018), 5.7%-13.0% (2019) and 5.5%-20.7% (2020), with an average increase of 6.8%-17.8% over the four years. When the amount of potassium applied was the same, the corn yield in the straw return treatment was higher than that in the straw removal treatment, with increases of 0.9%-2.9% (2017), 1.1%-6.6% (2018), 0.3%-5.9% (2019) and 1.1%-14.5% (2020), respectively, with an average increase of 0.9%-6.0% over the four years. In different potassium application treatments, corn yield increased first and then decreased with the increase in potassium application. In the first season of straw return, the yield increased with potassium application. 90 The corn yield of treatment was the highest, and from the second season onwards, the corn yield was K 60 The treatment was the highest. 90 Compared with the straw-off-field treatment, the highest yield potassium application rate treatment under straw-on-field (K 90 and 2018-2020 K 60 ) The corn yield was higher than the highest yield potassium application rate treatment (K 90 ), with an average increase of 2.3%. Figure 8 In the data, ns and * respectively indicate that there is no significant difference and significant difference at the 0.05 level between the treatments of returning straw to the field and removing straw from the field under the same nitrogen application rate; different lowercase letters respectively indicate that there is significant difference at the 0.05 level between different fertilization treatments under the conditions of returning straw to the field and removing straw from the field.

[0080] Regarding the potassium accumulation of corn treated with straw return and different potassium fertilizer dosages, refer to Fig. 9 , Fig. 9 -A is a schematic diagram showing potassium accumulation in corn at different potassium fertilizer dosages in 2017. Fig. 9 -B is a schematic diagram of potassium accumulation in corn with different potassium fertilizer dosages in 2018. Fig. 9-C represents the schematic diagram of potassium accumulation in corn with different potassium fertilizer dosages in 2019. Fig. 9 -D represents the schematic diagram of potassium accumulation in corn with different potassium fertilizer application rates in 2020. Potassium application treatment significantly affected the potassium accumulation of corn, while straw treatment had a significant effect on the potassium accumulation of corn from 2018 to 2020, and the interaction between the two factors reached a significant level between 2019 and 2020. In the same year, compared with different potassium fertilizer treatments (K0), potassium application with straw returned to the field and straw off the field significantly increased the potassium accumulation of corn ( P <0.05). When the potassium application rate was the same, the potassium accumulation in the straw return treatment was higher than that in the straw removal treatment, with increases of 1.2%-5.2% (2017), 2.0%-5.2% (2018), 0.9%-9.3% (2019), and 1.1%-5.1% (2020), respectively. The average increase over the four years was 0.9%-6.0%. In different potassium application treatments, the potassium accumulation of corn increased first and then decreased with the increase of potassium application rate. In the first season of straw return, the potassium accumulation rate was higher than that of straw removal treatment. 90 The corn yield of treatment was the highest, and from the second season onwards, the corn yield was K 60 The treatment was the highest. 90 Compared with straw leaving the field, the treatment with the highest potassium accumulation in straw returning to the field (K 90 and 2018-2020 K 60 ) were higher than the highest potassium application rate treatment (K 90 ), with an average increase of 3.4%. Fig. 9 In the data, ns and * respectively indicate that there is no significant difference and significant difference at the 0.05 level between the treatments of returning straw to the field and removing straw from the field under the same nitrogen application rate; different lowercase letters respectively indicate that there is significant difference at the 0.05 level between different fertilization treatments under the conditions of returning straw to the field and removing straw from the field.

[0081] Regarding the changes in soil available potassium content during the corn maturity period under straw returning and different potassium application treatments, straw returning and potassium fertilizer application rate had significant effects on soil exchangeable potassium content, while the interaction effect between the two factors on soil exchangeable potassium, non-exchangeable potassium and total potassium reached a significant level. In the same year, soil exchangeable potassium and non-exchangeable potassium content increased with the increase in potassium fertilizer application rate. Under the same potassium fertilizer application rate, soil exchangeable potassium and non-exchangeable potassium in the straw returning treatment were higher than those in the straw leaving the field treatment, with increases of 1.6%-4.0% (2017), 1.5%-4.7% (2018), 1.5%-5.8% (2019) and 1.3%-6.3% (2020), respectively; while there was no significant difference in total potassium content. Compared with the beginning of the experiment, under straw returning, K0 and K 30 The exchangeable and non-exchangeable potassium contents decreased, and the potassium fertilizer dosage increased to 60 kg / hm2 , the exchangeable potassium content and non-exchangeable potassium content of the soil were close to the initial values; while under the condition of straw leaving the field, K0, K 30 , K 90 and K 120 The contents of exchangeable potassium and non-exchangeable potassium decreased. When the potassium fertilizer dosage increased to 150 kg / hm 2 , the contents of soil exchangeable potassium and non-exchangeable potassium were close to the initial values, while the total potassium contents of different potassium application treatments were close to those at the beginning of the experiment.

[0082] Regarding the apparent balance of soil potassium under straw return and different potassium application treatments, except for the amount of crop carryout, fertilization and straw treatments significantly or extremely significantly affected the apparent profit and loss, balance coefficient and actual balance rate, and there was a significant interaction between the two. 2 The range increased significantly with the increase of potassium application rate. When the potassium application rate increased to 90 kg / hm 2 There was no significant difference in the amount of crop carried out ( P <0.05), and the amount of potassium applied when the straw is off the field is 0-90kg / hm 2 The range increases with the increase of potassium application rate. When the potassium application rate increases to 120kg / hm 2 There was no significant difference in the amount of crop carried out ( P <0.05). In the soil potassium deficit, the potassium deficit decreased with the increase of phosphorus application, and the potassium application rate of straw return treatment was 0-30kg / hm 2 Within this range, soil potassium is in a state of deficiency. When the potassium application rate is increased to 60 kg / hm 2 After the treatment, potassium was in a surplus state; while under the conditions of different potassium application rates, the straw-off-field treatment showed a deficit.

[0083] Example 4 shows that the present application has a positive effect on increasing corn yield. Potassium application has a very significant effect on yield. Compared with no potassium fertilizer (K0), potassium application under both straw return and off-field conditions significantly increased yield. The increase in straw return from 2017 to 2020 was 9.0%-17.0%, etc., and the average of four years was 7.8%-13.7%. The increase in straw off-field from 2017 to 2020 was 7.8%-19.5%, etc., and the average of four years was 6.8%-17.8%. When the amount of potassium application was the same, the yield of straw return was higher than that of straw off-field, with an increase of 0.9%-2.9% from 2017 to 2020, and an average of 0.9%-6.0% in four years, reflecting that straw return contributed to the increase in yield. In different potassium application treatments, the yield increased first and then decreased with the amount of potassium application. The yield of straw return in the first quarter was K 90 The highest yield, K from the second quarter 60 The highest, straw leaving the field is K 90The highest, clarifying the optimal potassium application amount for different straw treatments, can accurately guide fertilization; compared with straw leaving the field, the average increase in the highest yield potassium application amount under straw return to the field was 2.3%. Multi-dimensional data fully demonstrate that this application can effectively increase corn yields.

[0084] The experiment was a positioning experiment (2018-2019) using a single factor design and a nitrogen application rate of 210 g / hm2. 2 On this basis, six mixing ratios of slow-release nitrogen fertilizer and quick-acting nitrogen fertilizer were set: N: 100% PU (denoted as PU 100% ), N: 80% PU + 20% CRU (referred to as PU 80% ), N: 60% PU + 40% CRU (referred to as PU 60%) 、N:40%PU+60%CRU(denoted as PU 40%) 、N:20%PU+80%CRU(denoted as PU 20% ) and N: 100% CRU (denoted as PU0), and the treatment without nitrogen fertilizer (denoted as N0) was used as the control, for a total of 7 treatments. The amount of phosphorus and potassium fertilizers in each treatment was the same, both at 90 kg / hm 2 The fertilization method was to apply all nitrogen, phosphorus and potassium fertilizers as basal fertilizer before sowing. The tested corn variety was Fumin 985, and the planting density was 70,000 plants / hm2. 2 The sowing date is May 9 and the harvest period is October 4. The plot area is 40m 2 , repeated 3 times, and the plots were arranged randomly.

[0085] The aboveground biomass and nitrogen concentration were measured during the corn maturity stage; the yield, number of ears, number of kernels per ear, and 100-kernel weight were measured during the harvest stage.

[0086] Regarding corn yield and its components under different nitrogen fertilization treatments, fertilization treatments significantly or extremely significantly affected spring corn yield, number of kernels per ear, 100-kernel weight, and harvest index, while the year had no significant effect on corn yield, number of kernels per ear, 100-kernel weight, and harvest index, and there was no significant interaction between the two. Compared with the no nitrogen fertilization treatment (N0), the nitrogen fertilization treatments all had a significant yield-increasing effect ( P <0.05), with increases of 24.4%-40.2% (2018) and 43.6%-73.5% (2019), respectively. The reason for the yield difference is that the number of kernels per ear, 100-kernel weight and harvest index of corn in the nitrogen treatment are higher than those in the no nitrogen fertilizer (N0) treatment. In the different nitrogen treatments, the corn yield increases first and then decreases with the decrease of the proportion of quick-acting nitrogen fertilizer, and the PU60% treatment is the highest in both years.

[0087] In Example 5, the ratios of quick-acting nitrogen fertilizer to slow-release nitrogen fertilizer for obtaining the highest corn yield under the condition of returning straw to the field were 57:43 and 62:38, respectively, and the ratios of quick-acting nitrogen fertilizer to slow-release nitrogen fertilizer for obtaining the highest nitrogen absorption and utilization rate were 60:40 and 63:37, respectively.

[0088] The results of Example 5 show that fertilization treatment significantly affects spring corn yield, ear number, 100-grain weight and harvest index, and the year effect is not significant and there is no significant interaction between the two. Compared with N0, nitrogen treatments all significantly increase production, with an increase of 24.4%-40.2% in 2018 and an increase of 43.6%-73.5% in 2019, because the number of corn ears, 100-grain weight and harvest index treated with nitrogen are higher. In different nitrogen treatments, corn yield increases first and then decreases with the decrease in the proportion of quick-acting nitrogen fertilizer, and PU60% treatment is the highest in both years. In addition, it is also concluded that the ratio of quick-acting nitrogen fertilizer to slow-release nitrogen fertilizer to obtain the highest corn yield under the condition of returning straw to the field is 57:43 and 62:38 respectively. It shows that this application can significantly increase corn yield by rationally regulating the ratio of quick-acting nitrogen fertilizer to slow-release nitrogen fertilizer.

[0089] The experiment was a positioning experiment (2018-2019) using a single factor design and a nitrogen application rate of 210 g / hm2. 2 On this basis, a total of 6 basal application (jointing stage) ratio treatments were set: N100% basal application (denoted as N 10:0 )、N80% basal application + 20% topdressing (recorded as N 8:2 )、N60% basal application + 40% topdressing (recorded as N 6:4 )、N40% basal application + 60% topdressing (recorded as N 4:6 )、N20% basal application + 80% topdressing (recorded as N 2:8 ) and N100% topdressing (denoted as N 0:10 ), and the treatment without nitrogen fertilizer (denoted as N0) was used as the control, for a total of 14 treatments. The amount of phosphorus and potassium fertilizers in each treatment was the same, both at 90 kg / hm 2 The fertilization method was to apply all nitrogen, phosphorus and potassium fertilizers as basal fertilizer before sowing. The tested corn variety was Fumin 985, and the planting density was 70,000 plants / hm2. 2 The sowing date is May 9 and the harvest period is October 4. The plot area is 40m 2 , repeated 3 times, and the plots were arranged randomly.

[0090] The aboveground biomass and nitrogen concentration were measured during the corn maturity stage; the yield, number of ears, number of kernels per ear, and 100-kernel weight were measured during the harvest stage.

[0091] Fertilization treatment significantly affected spring maize yield, number of kernels per ear, and 100-kernel weight, while year had no significant effect on maize yield, number of kernels per ear, and 100-kernel weight, and there was no significant interaction between the two. Compared with the treatment without nitrogen fertilizer (N0), the nitrogen fertilizer treatment had a significant yield-increasing effect ( P <0.05), with increases of 24.4%-42.8% (2018) and 43.6%-70.2% (2019), respectively. The reason for the yield difference is that the number of kernels per ear, 100-kernel weight and harvest index of corn in the nitrogen application treatment were higher than those in the no nitrogen fertilizer (N0) treatment. In different nitrogen application treatments, corn yield increased first and then decreased with the decrease of the ratio of quick-acting nitrogen fertilizer. 4:6 The corn yield was the highest when the straw was returned to the field. The ratios of nitrogen fertilizer to base and topdressing fertilizer to obtain the highest corn yield were 35:65 and 45:55 respectively. The ratios of quick-acting nitrogen fertilizer to slow-release nitrogen fertilizer to obtain the highest nitrogen absorption and utilization rate were 33:67 and 41:59 respectively.

[0092] The positioning test of Example 6 was carried out in 2018-2019, and different base-following ratios of nitrogen fertilizer were studied for the straw return to the field conditions. The results show that fertilization treatment significantly affects spring corn yield, ear number and 100-grain weight, and the year effect is not significant and there is no significant interaction between the two. Compared with N0, nitrogen treatment significantly increased production, with an increase of 24.4%-42.8% in 2018 and an increase of 43.6%-70.2% in 2019, because the number of corn ears, 100-grain weight and harvest index of nitrogen treatment were higher. In different nitrogen treatments, corn yield increased first and then decreased with the decrease of the base application ratio of quick-acting nitrogen fertilizer, and the yield was the highest when the base-following ratio of quick-acting nitrogen fertilizer was N4:6. The base-following ratios of nitrogen fertilizers for obtaining the highest corn yield under the straw return to the field conditions were 35:65 and 45:55 respectively. In addition, the ratio of quick-acting nitrogen fertilizers to slow-release nitrogen fertilizers for obtaining the highest nitrogen absorption and utilization rate was obtained, indicating that this application can effectively increase corn yield by reasonably setting the base-following ratio of nitrogen fertilizers.

[0093] On the basis of clarifying the appropriate ratio of basal application and topdressing, in 2019, at the same nitrogen application rate (210kg / hm 2 ), a total of 4 topdressing treatments were set up, namely N100% basal application (recorded as N1), N40% basal application + 60% topdressing during the jointing period (recorded as N2), N40% basal application + 40% topdressing + 20% topdressing during the flowering period (recorded as N3) and N40% basal application + 30% topdressing + 15% topdressing during the flowering period + 15% topdressing during the filling period (recorded as N4), and the treatment without nitrogen fertilizer (recorded as N0) was used as the control, for a total of 5 treatments. The amount of phosphorus and potassium fertilizers in each treatment was the same, both 90kg / hm 2 The fertilization method was to apply all nitrogen, phosphorus and potassium fertilizers as basal fertilizer before sowing. The tested corn variety was Fumin 985, and the planting density was 70,000 plants / hm2. 2The sowing date is May 9 and the harvest period is October 4. The plot area is 40m 2 , repeated 3 times, and the plots were arranged randomly.

[0094] The aboveground biomass and nitrogen concentration were determined during the corn maturity stage. 0-100 cm soil samples were collected before corn sowing and after harvesting. 0-40 cm soil samples were collected during the corn seedling stage, jointing stage, mouth opening stage, flowering stage and grain filling stage. Every 20 cm was divided into one layer, and the inorganic nitrogen content was determined. The yield, number of ears, number of grains per ear, and 100-grain weight were determined during the harvest period.

[0095] Regarding corn yield and nitrogen use efficiency under different nitrogen fertilizer treatments, compared with the no nitrogen fertilizer treatment (N0), different nitrogen fertilizer treatments significantly increased corn yield ( P <0.05), with an increase of 17.5%-19.7%. Under the same nitrogen application rate, the corn yield of the treatments with delayed nitrogen fertilizer (N2, N3, N4) was significantly higher than that of the treatment with 100% basal fertilizer (N1; P <0.05). Among them, the yield increase of N3 treatment was the highest, which was 27.4% higher than that of 100% basal fertilizer treatment (N1), followed by N4 and N2 treatments.

[0096] Under the same nitrogen application rate, the nitrogen absorption and utilization rate, agronomic utilization rate, partial productivity and physiological utilization rate of the treatments (N2, N3, N4) with delayed nitrogen fertilizer were significantly higher than those of the treatment (N1) with 100% basal fertilizer. P <0.05), with increases of 27.5%-42.3%, 126.4%-182.4%, 18.9%-27.3%, and 11.5%-31.1%, respectively. The N3 treatment had the largest increase, followed by the N4 and N2 treatments. In addition, there was no significant difference in the nitrogen harvest index among the different nitrogen application treatments (P>0.05).

[0097] Regarding the changes in soil inorganic nitrogen content during the growth period of corn under different nitrogen application treatments, the inorganic nitrogen content of 0-20cm and 20-40cm soil during the entire growth period of corn first decreased and then increased with the advancement of the growth process, while under the same nitrogen application conditions, the inorganic nitrogen content of 0-20cm soil was higher than that of 20-40cm soil; compared with the treatment without nitrogen fertilizer application (N0), the nitrogen application treatment significantly increased the inorganic nitrogen content of 0-40cm soil (P<0.05); under the same nitrogen application rate, the inorganic nitrogen content of 0-20cm and 20-40cm soil was highest in the 100% basal fertilizer treatment (N1) from the seedling stage to the large mouth stage of corn, and the highest in the treatments with delayed nitrogen fertilizer (N2, N3, N4) from the flowering stage to the maturity stage, among which the highest was in the N2 treatment from the flowering stage to the flowering stage, the highest was in the N3 treatment during the filling stage, and the highest was in the N4 treatment during the maturity stage.

[0098] Under deep plowing and returning of straw to the field, the straw decomposition rate can reach more than 90% in the season. The decomposition and rapid nutrient release period of corn straw are between April and August. The straw nutrient release rate is potassium>phosphorus>carbon>nitrogen. By the end of the experiment, 78.2%-81.4% of carbon, 74.5%-78.2% of nitrogen, 85.1%-88.4% of phosphorus and 96.3%-97.1% of potassium in the straw were released. This is mainly because the release of nutrients is related to their existence in the straw. Potassium in the straw exists in ionic state and is easy to decompose and release; more than 60% of phosphorus exists in ionic state; carbon and nitrogen mainly exist in insoluble organic state, which decomposes slowly under natural conditions and has a low release rate.

[0099] Regarding the effect of returning straw to the field to replace chemical nitrogen, phosphorus and potassium fertilizers, the nitrogen fertilizer dosage required for the maximum corn yield under returning straw to the field and leaving the field in 2017, 2018, 2019 and 2020 was 203.7 kg / hm 2 、197.7kg / hm 2 、185.1kg / hm 2 、171.5kg / hm 2 and 209.7kg / hm 2 、204.9kg / hm 2 、203.5kg / hm 2 , 200.1kg / hm 2 ; Phosphate fertilizer dosages were 102.1kg / hm2 and 99.8kg / hm 2 , 95.3kg / hm2, 94.1kg / hm 2 and 109.8kg / hm 2 、106.7kg / hm 2 、106.6kg / hm 2 、108.7kg / hm 2 ; Potassium fertilizer dosage is 105.5kg / hm 2 、99.7kg / hm 2 、87.0kg / hm 2 、82.5kg / hm 2 and 111.9kg / hm 2 、110.5kg / hm 2 、111.5kg / hm 2 、108.5kg / hm 2 Compared with leaving the straw off the field, returning the straw to the field can reduce the amount of fertilizer used, and the reduction rate increases with the extension of the returning period. After returning the straw to the field for four seasons, the nitrogen, phosphorus and potassium fertilizers can be reduced by 14.3%, 13.4% and 24.0% respectively.

[0100] The different fertilization treatments under the conditions of straw return and straw removal showed the same performance. The absorption and utilization rate of nitrogen, phosphorus and potassium, agronomic utilization rate and partial productivity all showed a decreasing trend with the increase of nitrogen, phosphorus and potassium fertilizer application. Under the same fertilization conditions, the absorption and utilization rate of nitrogen, phosphorus and potassium, agronomic utilization rate and partial productivity of straw return treatment were higher than those of straw removal treatment.

[0101] In this embodiment, the different fertilization treatments under the conditions of returning straw to the field and leaving straw from the field showed the same performance. With the increase of fertilizer application, the inorganic nitrogen content of 0-40 cm soil, the effective phosphorus content of 0-20 cm soil, the exchangeable potassium and non-exchangeable potassium content all showed an increasing trend. Compared with the treatment of leaving straw from the field, at the same nitrogen, phosphorus and potassium levels, the treatment of returning straw to the field can increase the inorganic nitrogen content of 0-40 cm soil and the effective phosphorus, exchangeable potassium and non-exchangeable potassium content of 0-20 cm soil, while having no significant effect on the total phosphorus and total potassium content of the soil.

[0102] In summary, compared with leaving the straw off the field, returning the straw to the field can increase the nitrogen, phosphorus and potassium nutrient content in the soil, promote the absorption and utilization of nitrogen, phosphorus and potassium nutrients by corn, and thus increase corn yield and nitrogen, phosphorus and potassium fertilizer utilization efficiency. Taking 95% of the theoretical maximum yield potassium fertilizer dosage as the confidence interval, it is calculated that the appropriate nitrogen, phosphorus and potassium fertilizer dosages in the first two years of returning the straw to the field are 188.8-213.9 kg / hm 2 、95-107kg / hm 2 、94.7-110.8kg / hm 2 The appropriate amount of nitrogen, phosphorus and potassium fertilizers for returning to the field for three to four years is 163-194.4 kg / hm 2 , 90-100kg / hm 2 and 78.3-91.4kg / hm 2 between.

[0103] Regarding the optimal application ratio of quick-acting nitrogen fertilizer and slow-release nitrogen fertilizer under the condition of returning straw to the field, under the condition of returning straw to the field, corn yield, nitrogen fertilizer absorption and utilization rate, agronomic utilization rate and partial productivity all showed a trend of increasing first and then decreasing with the increase of the proportion of slow-release nitrogen fertilizer, and the highest ratio was 60%:40% for quick-acting nitrogen fertilizer and slow-release nitrogen fertilizer; when the slow-release nitrogen fertilizer exceeded this ratio, corn yield, nitrogen fertilizer absorption and utilization rate, agronomic utilization rate and partial productivity showed a downward trend. This shows that appropriately increasing the application ratio of quick-acting nitrogen fertilizer under the condition of returning straw to the field can reduce the stress of competing for nitrogen due to straw decomposition in the early growth period of corn, which is conducive to coordinating nitrogen absorption and utilization during the whole growth period, and improving corn yield and nitrogen utilization efficiency.

[0104] In this embodiment, the optimal ratios of quick-acting nitrogen fertilizer to slow-release nitrogen fertilizer for the highest corn yield and nitrogen absorption and utilization rate under the condition of returning straw to the field are 57%-62%:38%-43% and 60%-63%:37%-40%, respectively.

[0105] Regarding the different base-topdressing ratios of quick-acting nitrogen fertilizers under the conditions of straw returning to the field, under the conditions of straw returning to the field, corn yield, nitrogen absorption and utilization rate, agronomic utilization rate and partial productivity all showed a trend of first increasing and then decreasing with the increase of the base-topdressing ratio of nitrogen fertilizer. Among them, the corn yield, nitrogen absorption and utilization rate, agronomic utilization rate and partial productivity were the highest when the base-topdressing ratio of nitrogen fertilizer was 40%:60%. When the base-topdressing nitrogen fertilizer exceeded this ratio, the corn yield, nitrogen absorption and utilization rate, agronomic utilization rate and partial productivity showed a downward trend.

[0106] The application ratio of quick-acting nitrogen fertilizer and slow / controlled-release nitrogen fertilizer was fitted with the yield and nitrogen absorption and utilization rate, and the nitrogen fertilizer base and topdressing ratios for the highest corn yield and nitrogen absorption and utilization rate under the condition of straw returning to the field were 35%-45%:55%-65% and 33%-41%:59%-67%, respectively.

[0107] Regarding the determination of the best topdressing frequency of quick-acting nitrogen fertilizer under the condition of returning straw to the field, compared with one-time nitrogen application, the application of nitrogen fertilizer in batches can significantly increase corn yield, number of grains per ear and grain weight. Among them, the nitrogen fertilizer management method of basal fertilizer: jointing stage: flowering stage is 4:4:2, which has the highest yield, and the corresponding nitrogen harvest index and nitrogen utilization efficiency are also the highest. It can be seen that improper fertilizer management and asynchronous nutrient release and absorption are the main reasons for low corn yield.

[0108] Soil inorganic nitrogen is one of the nitrogen forms directly absorbed and utilized by plants, and its abundance and deficiency degree affects corn growth and development, and is the main factor determining yield. In the present embodiment, compared with 100% base fertilizer mode, the nitrogen fertilizer back-shift mode significantly improves 0-20cm and 20-40cm soil inorganic nitrogen content after corn flowering, and significantly reduces 40-100cm deep soil inorganic nitrogen content after corn harvest. Explanation: by back-shifting nitrogen fertilizer and increasing the number of nitrogen fertilizer topdressing, the soil continuous nitrogen supply capacity can be improved, and a good nitrogen nutrition environment is provided for the entire growth period of spring corn. And in the present embodiment, base fertilizer: jointing stage: flowering stage is 4:4:2 nitrogen fertilizer operation mode, and the inorganic nitrogen content of soil in corn flowering stage to filling stage is maintained at a higher level, and the obtained corn yield nitrogen utilization efficiency is also the highest. At the same time, in the nitrogen apparent balance of payments, the nitrogen input of this nitrogen application mode is basically balanced with the input, so that the nitrogen apparent loss rate is the lowest. Therefore, applying nitrogen fertilizer in two times according to 40% base fertilizer + 40% during the jointing stage + 20% during the flowering stage can better synchronize nutrient supply with crop absorption, thereby increasing yield and nitrogen utilization rate while reducing nitrogen loss.

Claims

1. A method for optimizing fertilization by returning straw to fields, characterized in that: include: Cut corn stalks into small pieces and air-dry them; In October and November of the same year, spread the air-dried corn stalks flat on the planting site at a depth of 20-30 cm; After returning the straw to the field, apply base fertilizer in combination with tillage operations; Use the nylon mesh bag method to return the straw to the field. Put the straw into a 200-300 mesh nylon mesh bag, seal it and spread it flat on the planting site at a depth of 20-30 cm, and separate the bags with soil.

2. The method for optimizing fertilization by returning straw to fields according to claim 1, characterized in that: When straw is returned to the field for 1-2 years, the nitrogen application rate is 188.8-213.9 kg / hm 2 In the case of returning straw to the field for 3-4 years, the nitrogen application rate is 163-194.4 kg / hm 2 between.

3. The method for optimizing fertilization by returning straw to fields according to claim 1, characterized in that: When straw is returned to the field for 1-2 years, the phosphorus application rate is 95-107 kg / hm 2 In the case of returning straw to the field for 3-4 years, the phosphorus application rate is 90-100 kg / hm2. 2 between.

4. The method for optimizing fertilization by returning straw to fields according to claim 1, characterized in that: When straw is returned to the field for 1-2 years, the application range of potassium fertilizer is 94.7-110.8 kg / hm 2 When straw is returned to the field for 3-4 years, the application range of potassium fertilizer is 78.3-91.4 kg / hm 2 .

5. The method for optimizing fertilization by returning straw to fields according to claim 2, characterized in that: include: In terms of mass percentage, the ratio of the total amount of quick-acting nitrogen fertilizer to the total amount of slow-release nitrogen fertilizer is (60-63): (37-40).

6. The method for optimizing fertilization by returning straw to fields according to claim 2, characterized in that: include: The nitrogen fertilizer application method is one of the following: basic fertilization, 40% basic fertilization + 60% topdressing during the jointing period, N40% basic fertilization + 40% topdressing + 20% topdressing during the flowering period, or N40% basic fertilization + 30% topdressing + 15% topdressing during the flowering period + 15% topdressing during the filling period.

7. The method for optimizing fertilization by returning straw to fields according to claim 2, characterized in that: include: 1-2 weeks before sowing, prepare a bacterial solution with the ratio of air-dried corn stalks, cellulose-decomposing bacteria and nitrogen-fixing bacteria of 100: (0.5-1): (0.3-0.5) by mass percentage, spray the bacterial solution onto the corn stalks, cover the treated corn stalks with plastic film, and compost and ferment for 7-10 days.

8. The method for optimizing fertilization by returning straw to fields according to claim 1, characterized in that: After returning the straw to the field and applying base fertilizer, collect the surrounding plant residues, crush them and spread them on the soil surface; Use a sprayer to spray the fermentation liquid prepared by mixing brown sugar, yeast and water in a mass ratio of 1:1:(8-10) on the laid plant residues.

9. The method for optimizing fertilization by returning straw to fields according to claim 7, characterized in that: After spraying on the soil surface, shallow tillage is performed, and the tillage depth is controlled at 5-10cm.

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