Fertilizer preparation method of special fertilizer for spring corn-soybean crop rotation system crops under straw returning

Abstract

The invention discloses a method for preparing a special fertilizer for crops of a spring corn-soybean crop rotation system under straw returning, and belongs to the technical field of spring corn-soybean crop rotation. According to the method, soil nutrient testing and the yield increasing effect of fertilization on crops are combined, and the nutrient supply level of soil is truly reflected; the habitual fertilization of farmers is optimized under the condition of comprehensively considering the nutrients brought in by the straws of previous crops, the nutrient release rate and the nutrient effectiveness of the straws, the relatively high carbon-nitrogen ratio under straw returning, and the apparent balance of phosphorus and potassium in the soil of a producing area. Compared with traditional farmer habitual fertilization, the optimized recommended fertilization formula provided by the invention not only contains previous crop straw nutrients, but also provides a special fertilizer formula for a main growth stage. The formula of the special fertilizer for the spring corn-soybean crop rotation system crops under straw returning not only can improve the yield of the crops, but also can improve the utilization efficiency of nutrients.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spring maize-soybean rotation, and particularly relates to a method for fertilizing a special fertilizer for crops in a spring maize-soybean rotation system under straw returning. BACKGROUND

[0002] Straw contains rich carbon, nitrogen, phosphorus and potassium elements, and is a valuable resource. Straw returning can not only increase the soil fertility and nutrient content, but also promote crop growth and improve crop yield and quality. At present, straw returning has become a routine operation in agricultural production, and its positive effects on improving soil fertility and soil structure are self-evident. For example, straw contains rich carbon sources, and after straw returning, the carbon in the straw is decomposed by soil microorganisms to form a large amount of organic carbon stored in the soil, thereby increasing the content of soil organic matter and fertilizing the soil. Straw returning increases the soil granular structure and the number of soil aggregates, and improves the soil porosity, thereby enhancing the water infiltration capacity and water retention capacity of the soil. In addition, straw returning also avoids the air pollution caused by straw burning and protects the environment. Straw burning produces a large amount of smoke, which affects air quality and even urban environment. Therefore, it is of great significance to fully utilize straw resources to improve the environment and effective utilization of crop resources.

[0003] However, the nutrients in the straw cannot be directly absorbed and utilized by crops, and must be decomposed by microorganisms, which requires a long process and involves the release rate of straw nutrients after returning. Although straw returning can improve the soil organic matter content, improve the soil structure and water retention capacity to a certain extent, it still faces many challenges in actual operation, such as how the nutrients of the straw after direct returning affect the fertilizer application rate, how to avoid the phenomenon of nitrogen competition between microorganisms and crops caused by the high soil carbon-nitrogen ratio after straw returning, and the like. Therefore, it is necessary to determine a reasonable fertilizer amount under straw returning.

[0004] Long-term high-intensity use plus straw non-return field leads to continuous decline of soil quality in northern areas, while farmers' extensive management such as "one shot" fertilization mode also causes crops to grow too long in early stage and lack nitrogen in late stage, resulting in low fertilizer utilization rate. Planting soybean has a positive impact on the sustainable development of agriculture. On the one hand, soybean has a protective effect on soil, which can promote the accumulation of soil organic matter and the improvement of soil quality. Soybean root system has strong nitrogen fixation capacity, which can reduce the dependence on chemical fertilizer, and can reduce the dependence of agriculture on chemical fertilizer and the environmental pollution caused by chemical fertilizer. With the change of people's dietary structure, the demand for soybean is increasing, but the yield of soybean is low, and the continuous planting also causes continuous cropping obstacles, so it is very important to study the combination of soybean rotation and crop diversity for improving the stability of farmland ecosystem. The spring corn and soybean rotation is one of the main planting modes in northeast China. However, the yield of spring corn is high, and the straw biomass is also large, which can significantly improve the soil nutrient content, but farmers do not pay attention to it, and the random fertilization on soybean also leads to the failure to exert the yield potential of soybean. If the straw nutrients in the corn-soybean rotation system are fully utilized, the soil nutrient balance and the overall quality of the soil can be improved, and part of the chemical fertilizer nutrients can be replaced, which can reduce the amount of fertilizer and increase the efficiency. However, when the straw is returned to the field, the difference in fertilizer requirement of crops in the rotation system, as well as the content of nutrients in the straw and the release rate of nutrients in the straw, will affect the amount of chemical fertilizer. Therefore, it is necessary to formulate a special fertilizer for spring corn-soybean rotation system under the condition of straw returning to field, so as to improve the yield of crops and the utilization efficiency of fertilizer. SUMMARY

[0005] The purpose of the present application is to provide a special fertilizer for spring corn-soybean rotation system under the condition of straw returning to field. That is, considering the amount of straw nutrient brought in by the previous crop and the release rate, combining the key parameters such as nutrient absorption, soil nutrient supply and fertilizer utilization rate, a calculation method of the nitrogen, phosphorus and potassium nutrient requirement ratio of special fertilizer at different growth stages of spring corn-soybean rotation system is proposed. This method is a technology for effectively improving the yield of spring corn-soybean rotation system, soil fertility and realizing the reduction of chemical fertilizer under the condition of straw returning to field, which can provide technical support for fertilizer manufacturers to provide special fertilizer formula for spring corn-soybean rotation system.

[0006] In order to achieve the above purpose, the present application provides the following technical scheme:

[0007] One of the technical schemes of the present application: a special fertilizer for spring corn-soybean rotation system under the condition of straw returning to field is provided, which comprises the following steps:

[0008] (1) Determine the soil nutrient supply grade according to the test value of soil nutrient in the plough layer before sowing:

[0009] The soil test indexes include organic matter, hydrolytic nitrogen, available phosphorus and available potassium; the soil nitrogen nutrient supply level is determined according to the content of soil organic matter and hydrolytic nitrogen, the soil phosphorus nutrient supply level is determined according to the content of available phosphorus, and the soil potassium nutrient supply level is determined according to the content of available potassium;

[0010] When the organic matter content is < 10 g / kg, the organic matter test level is "low"; when the organic matter content is 10-30 g / kg, the organic matter test level is "medium"; and when the organic matter content is > 30 g / kg, the organic matter test level is "high"; the "low", "medium" and "high" of the organic matter test level correspond to the "low", "medium" and "high" of the soil nitrogen supply level respectively; but when the soil hydrolytic nitrogen is ≥ 180 mg / kg, the organic matter test level "low" is upgraded to the test level "medium"; and when the hydrolytic nitrogen is ≤ 100 mg / kg, the organic matter test level "high" is downgraded to the test level "medium";

[0011] When the available phosphorus content is < 10 mg / kg, the available phosphorus test level is "low"; when the available phosphorus content is 10-25 mg / kg, the available phosphorus test level is "medium"; and when the available phosphorus content is > 25 mg / kg, the available phosphorus test level is "high"; the "low", "medium" and "high" of the available phosphorus test level correspond to the "low", "medium" and "high" of the soil phosphorus supply level respectively;

[0012] When the available potassium content is < 80 mg / kg, the available potassium test level is "low"; when the available potassium content is 80-150 mg / kg, the available potassium test level is "medium"; and when the available potassium content is > 150 mg / kg, the available potassium test level is "high"; the "low", "medium" and "high" of the available potassium test level correspond to the "low", "medium" and "high" of the soil potassium supply level respectively;

[0013] (2) Parameters for determining the "low", "medium" and "high" levels of soil nitrogen, phosphorus and potassium supply:

[0014] The nitrogen relative yield, phosphorus relative yield and potassium relative yield are calculated based on the yield of applying only two kinds of nitrogen, phosphorus and potassium fertilizers and the yield of full application of fertilizers;

[0015] Nitrogen relative yield = yield of applying only phosphorus and potassium ÷ yield of full application of nitrogen, phosphorus and potassium;

[0016] Phosphorus relative yield = yield of applying only nitrogen and potassium ÷ yield of full application of nitrogen, phosphorus and potassium;

[0017] Potassium relative yield = yield of applying only nitrogen and phosphorus ÷ yield of full application of nitrogen, phosphorus and potassium;

[0018] N groups of experiments are respectively performed to obtain N relative nitrogen yields, N relative phosphorus yields and N relative potassium yields; wherein the 25th percentile, the 50th percentile and the 75th percentile of the N relative nitrogen yields are determined as parameters of the nitrogen supply at the levels of "low", "medium" and "high"; the 25th percentile, the 50th percentile and the 75th percentile of the N relative phosphorus yields are determined as parameters of the phosphorus supply at the levels of "low", "medium" and "high"; and the 25th percentile, the 50th percentile and the 75th percentile of the N relative potassium yields are determined as parameters of the potassium supply at the levels of "low", "medium" and "high";

[0019] (3) Determining the nutrient demand per unit yield of the spring maize and soybean rotation system:

[0020] According to the QUEFTS model, the relationship between the grain yield and the above-ground nutrient absorption of each crop in the rotation system, and the relationship between the grain yield and the grain nutrient absorption are simulated, the above-ground nutrient absorption per unit yield and the grain nutrient absorption per unit yield are obtained, and the straw nutrient absorption per unit yield is calculated;

[0021] The straw nitrogen absorption per unit yield = the above-ground nitrogen absorption per unit yield - the grain nitrogen absorption per unit yield;

[0022] The straw phosphorus absorption per unit yield = the above-ground phosphorus absorption per unit yield - the grain phosphorus absorption per unit yield;

[0023] The straw potassium absorption per unit yield = the above-ground potassium absorption per unit yield - the grain potassium absorption per unit yield;

[0024] (4) Determining the fertilizer amount:

[0025] The fertilizer amount is determined in combination with the target yield of the spring maize and soybean, the nutrient demand per unit yield, the straw returning amount, the fertilizer utilization rate and the nutrient balance coefficient;

[0026] The nitrogen application amount = the target yield × (1 - the nitrogen supply level parameter) ÷ the nitrogen agronomic efficiency;

[0027] The nitrogen agronomic efficiency = a × (the target yield × (1 - the nitrogen supply level parameter)) 2 + b × the target yield × (1 - the nitrogen supply level parameter) + c;

[0028] wherein a, b and c are constant terms, the yield increase and the nitrogen agronomic efficiency of the applied nitrogen fertilizer are obtained according to a large number of previous field tests, the nitrogen fertilizer yield increase = the total yield of the nitrogen, phosphorus and potassium application - the yield of the application of only phosphorus and potassium = the target yield × (1 - the nitrogen supply level parameter), the nitrogen agronomic efficiency = (the total yield of the nitrogen, phosphorus and potassium application - the yield of the application of only phosphorus and potassium) ÷ the nitrogen application amount, the relationship between the nitrogen agronomic efficiency and the nitrogen fertilizer yield increase is fitted by using a quadratic equation, and the values of a, b and c are determined;

[0029] Phosphorus application rate = target yield × (1-relative phosphorus yield) × aboveground phosphorus absorption per unit yield ÷ phosphorus fertilizer utilization rate + target yield × phosphorus absorption per unit grain yield × phosphorus balance coefficient;

[0030] Among them, the phosphorus fertilizer utilization rate is calculated based on the utilization rate of the current season: 20% to 40% for spring corn and 20% to 40% for soybeans; the phosphorus balance coefficient determined based on the nutrient balance principle is 0.4 to 0.6 for spring corn and 0.3 to 0.5 for soybeans;

[0031] In order to take into account the proportion of straw returned to the fields and the apparent balance of soil phosphorus in spring corn and soybean producing areas, a balance coefficient was proposed to maintain the soil phosphorus surplus or deficit within the range of ±15% of aboveground phosphorus uptake.

[0032] Potassium application amount = target yield × (1-relative potassium yield) × potassium absorption per unit yield of aboveground parts ÷ potassium fertilizer utilization rate + target yield × potassium absorption per unit grain + target yield × potassium absorption per unit straw × potassium balance coefficient;

[0033] Among them, the utilization rate of potassium fertilizer is calculated according to the utilization rate of the season: 30% to 50% for spring corn and 30% to 50% for soybeans; the potassium balance coefficient determined according to the principle of nutrient balance is 0.1 to 0.5 for spring corn and 0.1 to 0.5 for soybeans;

[0034] In order to take into account the proportion of straw returned to the fields and the apparent balance of soil potassium in spring corn and soybean producing areas, a balance coefficient was proposed to maintain the surplus or deficit of soil potassium within the range of ±15% of aboveground potassium uptake.

[0035] (5) According to step (3), combined with the straw nutrient release rate and nutrient availability, determine the amount of nutrients brought in by the previous crop straw;

[0036] Amount of nitrogen brought in by the previous crop straw = nitrogen absorption by the previous crop straw × straw nitrogen release rate × nitrogen effectiveness;

[0037] Phosphorus amount brought in by the previous crop straw = phosphorus absorption amount of the previous crop straw × phosphorus release rate of straw × phosphorus availability;

[0038] Potassium amount brought in by the previous crop straw = potassium absorption amount of the previous crop straw × straw potassium release rate × potassium effectiveness;

[0039] Among them, the release rates of nitrogen, phosphorus and potassium nutrients from spring corn straw were 56.1%, 68.1% and 86.9% respectively, and the availability of nitrogen, phosphorus and potassium nutrients from spring corn straw to soybean season was 20%, 10% and 20% respectively;

[0040] The release rates of nitrogen, phosphorus and potassium nutrients from soybean straw were 61.4%, 48.5% and 85.4% respectively, and the availability of nitrogen, phosphorus and potassium nutrients from soybean straw to corn season was 30%, 20% and 30% respectively;

[0041] (6) According to step (4) and step (5), the final fertilizer nitrogen, phosphorus and potassium application amounts of spring maize and soybean are determined;

[0042] Final nitrogen application amount = nitrogen application amount - nitrogen amount brought by stalks of previous crop;

[0043] Final phosphorus application amount = phosphorus application amount - phosphorus amount brought by stalks of previous crop;

[0044] Final potassium application amount = potassium application amount - potassium amount brought by stalks of previous crop.

[0045] Preferably, the nitrogen, phosphorus and potassium in the spring maize special fertilizer are applied in several times, and are divided into spring maize base fertilizer special fertilizer and spring maize jointing special fertilizer, wherein the spring maize base fertilizer special fertilizer accounts for 60% of the final nitrogen application amount, the spring maize jointing special fertilizer accounts for 40% of the final nitrogen application amount; the spring maize base fertilizer special fertilizer accounts for 100% of the final phosphorus application amount; the spring maize base fertilizer special fertilizer and the spring maize jointing special fertilizer each accounts for 50% of the final potassium application amount.

[0046] The nitrogen, phosphorus and potassium in the soybean special fertilizer are applied once, and are soybean base fertilizer special fertilizer.

[0047] The beneficial technical effects of the present application are as follows:

[0048] The present application truly reflects the nutrient supply level of soil by combining soil nutrient testing with the yield-increasing effect of fertilization on crops; the habitual fertilization of farmers is optimized under the comprehensive consideration of the stalk-brought nutrients of previous crops, the nutrient release rate and availability of stalks, the higher carbon-nitrogen ratio under stalks returning to field, and the apparent balance of phosphorus and potassium in the soil of production area. Compared with the traditional habitual fertilization of farmers, the optimized recommended fertilization formula of the present application not only contains the stalk nutrients of previous crops, but also gives special fertilizer formula for main growth stages. The special fertilizer formula for crops in spring maize-soybean rotation system under stalks returning to field provided by the present application can not only improve the yield of crops, but also improve the nutrient use efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is a schematic diagram of the special fertilizer formula fertilization method for crops in spring maize-soybean rotation system under stalks returning to field in Example 1. DETAILED DESCRIPTION

[0050] Now a variety of exemplary embodiments of the present application will be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application. It should be understood that the terms described in the present application are only for describing the particular embodiments, and are not used to limit the present application.

[0051] It should be noted that the invention is not detailed in the place, which is the conventional means of operation in the art, and is not the focus of the invention.

[0052] In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. The intermediate value in any stated value or range, and each smaller range between any other stated value or intermediate value in the range, is also included in the present application. The upper limit and lower limit of these smaller ranges can be independently included or excluded from the range.

[0053] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described.

[0054] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" and the like are open-ended terms that are intended to permit but not limit the inclusion of elements or the number of elements not expressly listed.

[0055] The schematic diagram of the method for preparing the crop special fertilizer in the spring corn-soybean rotation system under the straw returning to field in the embodiment 1 of the present application is shown in the following table Figure 1 .

[0056] Embodiment 1

[0057] Step A1: Before the planting of crops, the soil samples are collected uniformly in the test plot, the soil samples in the plough layer, i.e. the soil samples in the 0-20cm are collected 5-8 drills, and are mixed uniformly. After the sampling is completed, the soil samples are air-dried in a cool place, sieved and analyzed for the organic matter, hydrolyzable nitrogen, available phosphorus and available potassium to understand the soil nutrient status of the recommended fertilization plot;

[0058] The test values of the soil before sowing are: organic matter 28.7g / kg, hydrolyzable nitrogen 153.1mg / kg, available phosphorus 23.9mg / kg and available potassium 176.4mg / kg.

[0059] Step A2: On the basis of step A1, the soil nitrogen, phosphorus and potassium nutrient supply grades are distinguished; wherein the soil nitrogen, phosphorus and potassium nutrient supply grades are related to the test results of the organic matter, available phosphorus and available potassium in the soil, and the specific relationship is shown in Table 1, wherein the organic matter content corresponds to the soil nitrogen supply grade, but when the soil hydrolyzable nitrogen is ≥180mg / kg, the test grade "low" of the organic matter is upgraded to the test grade "medium"; when the hydrolyzable nitrogen is ≤100mg / kg, the test grade "high" of the organic matter is downgraded to the test grade "medium";

[0060] Before sowing, the soil organic matter content was 28.7 g / kg, which was between 10 and 30 g / kg, and was considered medium. There was no need to adjust the soil nitrogen supply level, which was also considered medium. The available phosphorus content was 23.9 mg / kg, which was less than 25 mg / kg, and was considered medium. The available potassium content was 176.4 mg / kg, which was greater than 150 mg / kg, and was considered high.

[0061] It was finally determined that the soil nutrient test values ​​of the recommended fertilization plots corresponded to medium soil nitrogen and phosphorus supply levels, and high soil potassium supply levels.

[0062] Table 1 Soil nitrogen, phosphorus and potassium nutrient supply levels

[0063]

[0064] Step A3: Determine target yield:

[0065] Based on the yield of farmers' customary fertilization measures, spring corn and soybeans are both increased by 10%. For example, the farmers' customary yield of spring corn is 12t / ha, and the soybean yield is 3.5t / ha. The target yield is:

[0066] Spring corn: 12 + 12 × 10% = 13.2 t / ha;

[0067] Soybeans: 3.5 + 3.5 × 10% = 3.85 t / ha;

[0068] Step A4: Determine soil nitrogen, phosphorus, and potassium nutrient supply level parameters:

[0069] The relative yields of nitrogen, phosphorus and potassium were calculated based on the yields of applying only two of the nitrogen, phosphorus and potassium fertilizers and the yields of applying all fertilizers;

[0070] Relative nitrogen yield = yield of phosphorus and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined;

[0071] Relative phosphorus yield = yield of nitrogen and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined;

[0072] Relative potassium yield = yield of nitrogen and phosphorus alone ÷ yield of nitrogen, phosphorus and potassium combined;

[0073] There are 1272, 1023, and 1093 data points on the relative yields of nitrogen, phosphorus, and potassium for spring corn, respectively;

[0074] There are 502, 467, and 474 data on the relative yields of nitrogen, phosphorus, and potassium in soybean soils, respectively;

[0075] The 25th, 50th, and 75th percentiles of the relative yields of nitrogen, phosphorus, and potassium were determined as parameters for the “low,” “medium,” and “high” levels of nitrogen, phosphorus, and potassium supply;

[0076] The obtained nitrogen, phosphorus, and potassium soil nutrient supply level parameters of spring maize and soybean are shown in Table 2.

[0077] Table 2 Corresponding table of nitrogen, phosphorus, and potassium soil nutrient supply level parameters of spring maize and soybean The soil nitrogen, phosphorus, and potassium nutrient supply levels are determined by step A2, and the corresponding spring maize soil nitrogen, phosphorus, and potassium level parameters are 0.747, 0.864, and 0.925, respectively, and the corresponding soybean soil nitrogen, phosphorus, and potassium level parameters are 0.858, 0.875, and 0.926, respectively, in combination with the obtained supply level parameters in Table 2.

[0078] Step A5: Determining the nutrient requirement per unit yield:

[0079] First, collect field test data of spring maize and soybean or arrange field tests, and the data must include grain yield, straw yield, and nitrogen, phosphorus, and potassium nutrient uptake;

[0080] Further, the QUEFTS model is applied to simulate the quantitative relationship between grain yield and aboveground nutrient uptake;

[0081] Then, the aboveground nutrient requirement per unit yield is obtained by using the target yield of 80% of the potential yield as the final aboveground nutrient requirement per unit yield;

[0082] The calculated aboveground nitrogen, phosphorus, and potassium nutrient requirements per unit yield of spring maize are 18.2, 4.7, and 15.8 kg / t, respectively, and the aboveground nitrogen, phosphorus, and potassium nutrient requirements per unit yield of soybean are 55.4, 7.9, and 20.1 kg / t, respectively;

[0083] Further, the QUEFTS model is applied to simulate the quantitative relationship between grain yield and grain nutrient uptake, and the grain nutrient requirement per unit yield is calculated;

[0084] The calculated grain nitrogen, phosphorus, and potassium nutrient requirements per unit yield of spring maize are 10.7, 2.9, and 3.3 kg / t, respectively, and the grain nitrogen, phosphorus, and potassium nutrient requirements per unit yield of soybean are 48.3, 5.9, and 12.2 kg / t, respectively.

[0085] Step A6: Determining the straw nutrient uptake per unit yield:

[0086] The spring maize straw nitrogen uptake is 18.2-10.7=7.5 kg / t;

[0087] The spring maize straw phosphorus uptake is 4.7-2.9=1.8 kg / t;

[0088] The spring maize straw potassium uptake is 15.8-3.3=12.5 kg / t;

[0089] Soybean straw nitrogen uptake = 55.4-48.3 = 7.1 kg / t;

[0090] Soybean straw phosphorus uptake = 7.9-5.9 = 2.0 kg / t;

[0091] Soybean straw potassium uptake = 20.1-12.2 = 7.9 kg / t.

[0092] Step A7: Determine the recommended amount of nitrogen, phosphorus and potassium nutrients:

[0093] Combined with the spring corn-soybean target yield, unit yield nutrient demand, straw return amount, fertilizer utilization rate, and nutrient balance coefficient to determine the fertilizer nutrient demand;

[0094] Adjust the fertilizer recovery rate in the season, among them, the spring corn phosphorus and potassium recovery rates are adjusted to 30% and 50% respectively; the soybean phosphorus and potassium recovery rates are adjusted to 20% and 40% respectively;

[0095] Determine the nutrient balance coefficient, among them, the spring corn grain phosphorus and straw potassium nutrient balance coefficients are determined to be 0.5 and 0.1 respectively; the soybean grain phosphorus and straw potassium nutrient balance coefficients are determined to be 0.4 and 0.15 respectively;

[0096] Calculate the amount of nitrogen, phosphorus and potassium:

[0097] Spring corn:

[0098] According to a large number of field tests in the past, it is determined that in the main production area of spring corn-soybean in Northeast China, the calculation formula of nitrogen agronomic efficiency of spring corn is a = -0.3451, b = 6.142, and c = 0.0354;

[0099] Nitrogen application amount = (13.2 x (1-0.747) x 1000) ÷ [-0.3451 x (13.2 x (1-0.747)) 2 + 6.142 x 13.2 x (1-0.747) + 0.0354] = 200.0 kg / ha;

[0100] Phosphorus application amount = 13.2 x (1-0.864) x 4.7 ÷ 30% + 13.2 x 2.9 x 0.5 = 47.3 kg / ha;

[0101] Potassium application amount = 13.2 x (1-0.925) x 15.8 ÷ 50% + 13.2 x 3.3 + 13.2 x 12.5 x 0.1 = 91.3 kg K / ha;

[0102] Soybean:

[0103] According to a large number of field tests in the past, it is determined that the nitrogen agricultural efficiency calculation formula of soybean in the main production area of spring maize-soybean in Northeast China is a=-10, b=23.5, and c=-0.05;

[0104] The amount of nitrogen applied is (3.85x(1-0.858)x1000) / [-10.0x(3.85x(1-0.858)) 2 +23.5x3.85x(1-0.858)-0.05]=55.7kg / ha;

[0105] The amount of phosphorus applied is 3.85x(1-0.875)x7.9 / 20%+3.85x5.9x0.4=28.1kg / ha;

[0106] The amount of potassium applied is 3.85x(1-0.926)x20.1 / 40%+3.85x12.2+3.85x7.9x0.15=65.8kg / ha.

[0107] Step A8: Determine the amount of nutrients brought in by the previous crop straw, where the previous crop of spring maize is soybean, and the farmer's yield is 3.5t / ha, and the previous crop of soybean is spring maize, and the farmer's yield is 12t / ha;

[0108] The nitrogen, phosphorus, and potassium nutrient release rates of soybean straw in the spring maize planting season are 61.4%, 48.5%, and 85.4%, respectively, and the nitrogen, phosphorus, and potassium nutrient release rates of spring maize straw in the soybean planting season are 56.1%, 68.1%, and 86.9%, respectively;

[0109] The nitrogen, phosphorus, and potassium availability of soybean straw in the spring maize planting season is 30%, 20%, and 30%, respectively, and the nitrogen, phosphorus, and potassium availability of spring maize straw in the soybean planting season is 20%, 10%, and 20%, respectively;

[0110] The amount of nutrients brought in by the previous crop of soybean straw before spring maize planting is:

[0111] The amount of nitrogen brought in by the previous crop of soybean straw is 3.5x7.1x61.4%x30%=4.6kg / ha;

[0112] The amount of phosphorus brought in by the previous crop of soybean straw is 3.5x2.0x48.5%x20%=0.7kg / ha;

[0113] The amount of potassium brought in by the previous crop of soybean straw is 3.5x7.9x85.4%x30%=7.1kg / ha;

[0114] The amount of nutrients brought in by the previous crop of spring maize straw before soybean planting is:

[0115] The amount of nitrogen brought in by the previous crop of spring maize straw is 12x7.5x56.1%x20%=10.1kg / ha;

[0116] The amount of phosphorus brought in by the previous spring corn stalks = 12 x 1.8 x 68.1% x 10% = 1.5 kg / ha;

[0117] The amount of potassium brought in by the previous spring corn stalks = 12 x 12.5 x 86.9% x 20% = 26.1 kg / ha.

[0118] Step A9: Determine the final fertilizer N, P, K amount for spring corn-soybean rotation system:

[0119] Spring corn:

[0120] Final N application amount = 200.0 - 4.6 = 195.4 kg / ha;

[0121] Final P application amount = 47.3 - 0.7 = 46.6 kg / ha;

[0122] Final K application amount = 91.3 - 7.1 = 84.2 kg / ha;

[0123] Soybean:

[0124] Final N application amount = 55.7 - 10.1 = 45.6 kg / ha;

[0125] Final P application amount = 28.1 - 1.5 = 26.6 kg / ha;

[0126] Final K application amount = 65.8 - 26.1 = 39.8 kg / ha.

[0127] Step A10: Determine the N, P2O5, K2O ratio of special fertilizer for main growth stages during the growth period of spring corn-soybean rotation under straw returning:

[0128] Spring corn growth period fertilization stages are at the seeding period and the jointing period, corresponding to spring corn special fertilizer as base fertilizer special fertilizer and jointing special fertilizer; N is calculated according to the base and top-up ratio of 60%:40%, P is all base fertilizer, and K is calculated according to the base and top-up ratio of 50%:50%;

[0129] According to the final N, P, K application amount and the N, P, K application method of spring corn, the N, P, K application amount in base fertilizer special fertilizer is 117.2, 46.6, 42.1 kg / ha, which is converted to N, P2O5, K2O as 117.2, 46.6 x 2.292, 42.1 x 1.205, i.e. 117.2, 106.8, 50.7 kg / ha;

[0130] According to the final nitrogen, phosphorus and potassium application amounts and the nitrogen, phosphorus and potassium application methods of spring maize, the N, P and K application amounts in the jointing special fertilizer are determined as 78.2, 0 and 42.1 kg / ha respectively, which are converted into N, P2O5 and K2O as 78.2, 0 and 50.7 kg / ha respectively;

[0131] The soybean growth period fertilization stages are all base fertilization special fertilizers;

[0132] According to the final nitrogen, phosphorus and potassium application amounts and the nitrogen, phosphorus and potassium application methods of soybean, the N, P and K application amounts in the base special fertilizer are determined as 45.6, 26.6 and 39.8 kg / ha respectively, which are converted into N, P2O5 and K2O as 45.6, 61.0 and 47.9 kg / ha respectively;

[0133] Finally, the total nutrient content and the corresponding N:P2O5:K2O grade of the spring maize-soybean special fertilizer are determined according to the GB 15063-2001 standard respectively.

[0134] In the main production area of spring maize-soybean in Northeast China, the conventional fertilization and the optimized fertilization are set as two scenarios for comparison, and both of the two fertilization scenarios are carried out under the condition of straw returning to field, so as to verify the rationality of the optimized fertilization under the condition of straw returning to field. The verification parameters include the yield, the fertilization amount, the nitrogen, phosphorus and potassium nutrient recovery rate under different fertilization scenarios, and the results are shown in Table 3.

[0135] Table 3

[0136]

[0137] Note: The fertilization amount of the optimized fertilization in Table 3 is the recommended amount, which takes into account the amount of straw nutrient brought in by the previous crop.

[0138] Table 3 shows the effects of different fertilization scenarios on the yield and nutrient recovery rate of the spring maize-soybean rotation system. The field test results show that, for spring maize, compared with the conventional fertilization, the yield of the optimized fertilization is increased by 6.6%; the nitrogen, phosphorus and potassium fertilizer application amounts are reduced by 15.0%, 11.0% and 15.5% respectively; the nitrogen fertilizer recovery rate is increased by 15.5 percentage points, the phosphorus fertilizer recovery rate is increased by 12.5 percentage points, and the potassium fertilizer recovery rate is increased by 18.4 percentage points. For soybean, compared with the conventional fertilization, the yield of the optimized fertilization is increased by 7.4%; the nitrogen, phosphorus and potassium fertilizer application amounts are reduced by 29.8%, 32.2% and 20.2% respectively; the nitrogen fertilizer recovery rate is increased by 20.3 percentage points, the phosphorus fertilizer recovery rate is increased by 8.8 percentage points, and the potassium fertilizer recovery rate is increased by 18.9 percentage points.

[0139] After the previous crop straw is returned to the field, the nutrients in the straw cannot be directly absorbed and utilized by crops, and must be decomposed by microorganisms. The carbon-nitrogen ratio suitable for microbial decomposition is usually 25:1, but the carbon-nitrogen ratio in the straw is more than 80:1. If the nitrogen supply in the soil is insufficient, it will lead to the phenomenon of microorganisms and crops competing for nitrogen, and crops will lack nitrogen and appear weak. Corn straw is rich in carbon, and soybean straw contains high nitrogen. Rotation and matching of straw returning to the field can coordinate the carbon-nitrogen ratio, promote microbial activity, and release phosphorus, potassium and other nutrients. The high nitrogen requirement of corn and the nitrogen fixation of soybean in the rotation system can break the continuous cropping obstacles and balance the utilization of soil nutrients. The current optimization of fertilization can significantly reduce the amount of fertilization compared with the current farmer's habit of fertilization. Through the slow-release effect of straw returning to the field, combined with precise fertilization according to the needs of rotation, the amount of fertilization can be further reduced, and nutrient waste can be avoided, which has a significant effect on yield and fertilizer utilization rate. At the same time, the effect of straw returning to the field on improving soil structure, increasing soil organic matter content and enhancing water and fertilizer retention capacity cannot be ignored. Therefore, straw returning to the field combined with optimized fertilizer can reduce the amount of fertilization, reduce the cost of fertilizer investment for farmers, reduce environmental pollution caused by straw burning, meet the policy guidance of green agriculture, and realize sustainable development of agriculture.

[0140] The above-described embodiments are merely preferred modes of the present application and are not intended to limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design spirit of the present application shall fall within the scope of protection of the present application as defined by the claims.

Claims

1. A method for preparing fertilizers for crops in a spring corn-soybean rotation system under straw return, characterized in that: The following steps are involved: (1) Determine the soil nutrient supply level based on the soil nutrient test value before sowing: The soil test indicators include organic matter, hydrolyzable nitrogen, available phosphorus and available potassium; the soil nitrogen nutrient supply level is determined based on the content of soil organic matter and hydrolyzable nitrogen, the soil phosphorus nutrient supply level is determined based on the content of soil available phosphorus, and the soil potassium nutrient supply level is determined based on the content of soil available potassium; Among them, when the organic matter content is <10g / kg, the organic matter test level is "low", when the organic matter content is 10-30g / kg, the organic matter test level is "medium", and when the organic matter content is >30g / kg, the organic matter test level is "high"; the organic matter test levels of "low", "medium" and "high" correspond to the soil nitrogen supply levels of "low", "medium" and "high" respectively; however, when the soil hydrolyzable nitrogen is ≥180mg / kg, the organic matter test level of "low" is upgraded to the test level of "medium"; when the hydrolyzable nitrogen is ≤100mg / kg, the organic matter test level of "high" is downgraded to the test level of "medium"; When the available phosphorus content is less than 10 mg / kg, the available phosphorus test grade is "low", when the available phosphorus content is between 10 and 25 mg / kg, the available phosphorus test grade is "medium", and when the available phosphorus content is greater than 25 mg / kg, the available phosphorus test grade is "high". The "low", "medium" and "high" available phosphorus test grades correspond to the "low", "medium" and "high" soil phosphorus supply grades, respectively. When the available potassium content is less than 80 mg / kg, the available potassium test level is "low", when the available potassium content is between 80 and 150 mg / kg, the available potassium test level is "medium", and when the available potassium content is greater than 150 mg / kg, the available potassium test level is "high". The "low", "medium" and "high" levels of the available potassium test correspond to the "low", "medium" and "high" levels of soil potassium supply, respectively. (2) Determine the parameters for "low", "medium" and "high" levels of soil nitrogen, phosphorus and potassium supply: The relative yields of nitrogen, phosphorus and potassium were calculated based on the yields of applying only two of the nitrogen, phosphorus and potassium fertilizers and the yields of applying all fertilizers; Relative nitrogen yield = yield of phosphorus and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined; Relative phosphorus yield = yield of nitrogen and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined; Relative potassium yield = yield of nitrogen and phosphorus alone ÷ yield of nitrogen, phosphorus and potassium combined; N groups of experiments were conducted to obtain N nitrogen relative yields, N phosphorus relative yields, and N potassium relative yields; among them, the 25th, 50th, and 75th percentiles of the N nitrogen relative yields were determined as parameters for the "low", "medium", and "high" levels of nitrogen supply; the 25th, 50th, and 75th percentiles of the N phosphorus relative yields were determined as parameters for the "low", "medium", and "high" levels of phosphorus supply; and the 25th, 50th, and 75th percentiles of the N potassium relative yields were determined as parameters for the "low", "medium", and "high" levels of potassium supply. (3) Determine the nutrient requirements per unit yield of the spring corn and soybean rotation system: The relationship between grain yield and aboveground nutrient absorption of each crop in the rotation system, as well as the relationship between grain yield and grain nutrient absorption, was simulated based on the QUEFTS model. The aboveground nutrient absorption and grain nutrient absorption per unit yield were obtained, and the straw nutrient absorption per unit yield was calculated. Nitrogen absorption of straw per unit yield = nitrogen absorption of aboveground part per unit yield - nitrogen absorption of grain per unit yield; Phosphorus absorption of straw per unit yield = phosphorus absorption of aboveground part per unit yield - phosphorus absorption of grain per unit yield; Potassium absorption of straw per unit yield = potassium absorption of aboveground part per unit yield - potassium absorption of grain per unit yield; (4) Determine the amount of fertilizer: The fertilizer dosage is determined based on the target yield of spring corn and soybeans, nutrient requirements per unit yield, straw return amount, fertilizer utilization rate, and nutrient balance coefficient; Nitrogen application rate = target yield × (1-nitrogen supply level parameter) ÷ nitrogen agronomic efficiency; Nitrogen agronomic efficiency = a × (target yield × (1-nitrogen supply level parameter)) 2 + b × target yield × (1-nitrogen supply level parameter) + c; Where a, b, and c are constant terms. Based on a large number of previous field experiments, the yield increase and nitrogen agronomic efficiency of nitrogen fertilizer application were obtained: nitrogen fertilizer yield increase = total nitrogen, phosphorus, and potassium yield - yield of phosphorus and potassium alone = target yield × (1-nitrogen supply level parameter); nitrogen agronomic efficiency = (total nitrogen, phosphorus, and potassium yield - yield of phosphorus and potassium alone) / nitrogen application rate. A quadratic equation was used to fit the relationship between nitrogen agronomic efficiency and nitrogen fertilizer yield increase to determine the values ​​of a, b, and c. Phosphorus application rate = target yield × (1-relative phosphorus yield) × aboveground phosphorus absorption per unit yield ÷ phosphorus fertilizer utilization rate + target yield × phosphorus absorption per unit grain yield × phosphorus balance coefficient; Among them, the phosphorus fertilizer utilization rate is calculated based on the utilization rate of the current season: 20% to 40% for spring corn and 20% to 40% for soybeans; the phosphorus balance coefficient determined based on the nutrient balance principle is 0.4 to 0.6 for spring corn and 0.3 to 0.5 for soybeans; Potassium application amount = target yield × (1-relative potassium yield) × potassium absorption per unit yield of aboveground parts ÷ potassium fertilizer utilization rate + target yield × potassium absorption per unit grain + target yield × potassium absorption per unit straw × potassium balance coefficient; Among them, the utilization rate of potassium fertilizer is calculated according to the utilization rate of the season: 30% to 50% for spring corn and 30% to 50% for soybeans; the potassium balance coefficient determined according to the principle of nutrient balance is 0.1 to 0.5 for spring corn and 0.1 to 0.5 for soybeans; (5) According to step (3), combined with the straw nutrient release rate and nutrient availability, determine the amount of nutrients brought in by the previous crop straw; Amount of nitrogen brought in by the previous crop straw = nitrogen absorption by the previous crop straw × straw nitrogen release rate × nitrogen effectiveness; Phosphorus amount brought in by the previous crop straw = phosphorus absorption amount of the previous crop straw × phosphorus release rate of straw × phosphorus availability; Potassium amount brought in by the previous crop straw = potassium absorption amount of the previous crop straw × straw potassium release rate × potassium effectiveness; Among them, the release rates of nitrogen, phosphorus and potassium nutrients from spring corn straw were 56.1%, 68.1% and 86.9% respectively, and the availability of nitrogen, phosphorus and potassium nutrients from spring corn straw to soybean season was 20%, 10% and 20% respectively; The release rates of nitrogen, phosphorus and potassium nutrients from soybean straw were 61.4%, 48.5% and 85.4% respectively, and the availability of nitrogen, phosphorus and potassium nutrients from soybean straw to corn season was 30%, 20% and 30% respectively; (6) Determine the final nitrogen, phosphorus, and potassium fertilizer application rates for spring corn and soybeans based on steps (4) and (5); Final nitrogen application amount = nitrogen application amount - nitrogen amount brought in by the previous crop straw; Final phosphorus application amount = phosphorus application amount - phosphorus amount brought in by the previous crop straw; Final potassium application amount = potassium application amount - potassium amount brought in by the previous crop straw.

2. The method for preparing fertilizer for crops in the spring corn-soybean rotation system under straw return to field according to claim 1, characterized in that: The nitrogen, phosphorus and potassium in the spring corn special fertilizer are applied in batches, and are divided into a spring corn base fertilizer special fertilizer and a spring corn jointing special fertilizer, wherein the spring corn base fertilizer special fertilizer accounts for 60% of the final nitrogen application amount, and the spring corn jointing special fertilizer accounts for 40% of the final nitrogen application amount; the spring corn base fertilizer special fertilizer accounts for 100% of the final phosphorus application amount; the spring corn base fertilizer special fertilizer and the spring corn jointing special fertilizer each account for 50% of the final potassium application amount; The nitrogen, phosphorus and potassium in the soybean fertilizer are applied at one time, and it is a special fertilizer for soybean base fertilizer.

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