Fertilizer preparation method of special fertilizer for winter rape-middle-season rice rotation system crops under straw returning

Abstract

The invention discloses a method for preparing a special fertilizer for winter rape-middle-season rice crop rotation system crops under straw returning, and belongs to the technical field of rape-rice 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 winter rape-middle-season rice 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 rape-rice rotation, and particularly relates to a method for preparing a special fertilizer for crops in a winter rape-mid-season rice rotation system under straw field returning. BACKGROUND

[0002] Straw contains a large amount of nitrogen, phosphorus and potassium elements, and is a valuable resource. As a byproduct of agricultural production, straw field returning is currently a common practice, which has a significant positive effect on soil physical and chemical properties and crop yield. Straw field returning is an important source of soil organic carbon, which can not only fertilize the soil and increase crop productivity, but also improve soil structure and increase soil aggregate stability. After straw is returned as an organic matter, it can provide high-carbon molecular compounds for microorganisms. The carbon in the straw is decomposed by soil microorganisms to form humus, which ultimately increases soil organic carbon and plays a role in fertilizing the soil. At the same time, straw field returning can promote the transformation of microaggregates to macroaggregates and improve soil porosity, thereby enhancing the water infiltration and retention capacity of the soil. However, in production, straw is often randomly piled up in the field or burned, which produces a large amount of greenhouse gases or smoke, affecting air quality and even urban environment. Therefore, straw field returning is of great significance to improving the environment and effective utilization of crop resources.

[0003] After crop straw is returned to the field, it can slowly release nutrients during the decomposition process, which not only balances the soil pH, but also increases the soil available nutrient content, improves the soil microbial community structure, and improves the soil microecological environment. However, the nutrients in the straw cannot be directly absorbed and utilized by crops, and must be decomposed by microorganisms, which takes a long time. In addition, the release rate of nutrients in straw varies in different growth environments, and the proportion of nitrogen, phosphorus and potassium elements in different straws also varies. Therefore, in the actual nutrient management process, it is necessary to use different amounts of chemical fertilizers in combination with straw field returning in different crop rotation systems.

[0004] Winter rape-middle rice rotation system is the main planting system in the Yangtze River Basin, and the specific improvement of multiple cropping index. Winter rape has deep root system, which can improve soil structure, and its fallen leaves and straw returned to field can increase organic matter and reduce the dependence on chemical fertilizer for rice planting. Winter rape mulching can reduce soil exposure and inhibit greenhouse gas emission, and winter rape-rice rotation can improve unit area output value. However, the winter rape-middle rice rotation system also faces the problem of excessive application, which leads to resource waste and environmental pollution. Straw contains rich nitrogen, phosphorus and potassium elements, and has high substitution potential for fertilizer. If the part of nutrients is fully utilized, the efficiency of reducing and increasing fertilizer will be further improved. At present, in the winter rape-middle rice rotation system, the nutrient amount and release rate of straw returned to field in the process of nutrient management are not fully considered, and the optimal nutrient allocation ratio at different growth stages after straw returned to field is lacked, so it is necessary to prepare crop special fertilizer for winter rape-middle rice rotation system under the condition of straw returned to field, so as to improve crop yield and fertilizer utilization efficiency. SUMMARY

[0005] The purpose of the present application is to provide a method for preparing crop special fertilizer for winter rape-middle rice rotation system under the condition of straw returned to field. That is, under the condition of considering the nutrient amount and release rate of straw of the previous crop, by optimizing the key parameters such as nutrient absorption, soil nutrient supply and fertilizer utilization rate, a method for calculating the ratio of nitrogen, phosphorus and potassium nutrient demand of special fertilizer at different growth stages of winter rape-middle rice rotation system is proposed. The method is a technology for effectively improving crop yield and soil fertility of winter rape-middle rice rotation system under the condition of straw returned to field, and realizing the reduction and increase of chemical fertilizer, which can provide technical support for fertilizer manufacturers to provide formula of crop special fertilizer for winter rape-middle rice 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 provides a method for preparing crop special fertilizer for winter rape-middle rice rotation system under the condition of straw returned to field, which comprises the following steps:

[0008] (1) determining soil nutrient supply grade according to pre-sowing soil nutrient test value:

[0009] The soil test indexes include organic matter, hydrolyzable nitrogen, available phosphorus and available potassium; the soil nitrogen nutrient supply grade is determined according to the content of soil organic matter and hydrolyzable nitrogen, the soil phosphorus nutrient supply grade is determined according to the content of soil available phosphorus, and the soil potassium nutrient supply grade is determined according to the content of soil 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 hydrolyzable nitrogen is ≥150 mg / kg, the organic matter test level "low" is upgraded to the test level "medium"; and when the hydrolyzable 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 applying all the fertilizers;

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

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

[0017] Potassium relative yield = yield of applying only nitrogen and phosphorus ÷ yield of applying all the 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 winter rape and medium rice in the crop rotation system:

[0020] According to the QUEFTS model, the relationships between grain yield and aboveground nutrient uptake of each crop in the crop rotation system, and the relationships between grain yield and grain nutrient uptake are simulated, the aboveground nutrient uptake per unit yield and the grain nutrient uptake per unit yield are obtained, and the straw nutrient uptake per unit yield is calculated;

[0021] The straw nitrogen uptake per unit yield = the aboveground nitrogen uptake per unit yield - the grain nitrogen uptake per unit yield;

[0022] The straw phosphorus uptake per unit yield = the aboveground phosphorus uptake per unit yield - the grain phosphorus uptake per unit yield;

[0023] The straw potassium uptake per unit yield = the aboveground potassium uptake per unit yield - the grain potassium uptake per unit yield;

[0024] (4) Determining the fertilizer amount:

[0025] The fertilizer amount is determined in combination with the target yield of winter rape and medium rice, 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 yield of the full application of nitrogen, phosphorus and potassium - the yield of the application of only phosphorus and potassium = the target yield × (1 - the nitrogen supply level parameter), the nitrogen agronomic efficiency = (the yield of the full application of nitrogen, phosphorus and potassium - 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] Amount of phosphorus application = target yield x (1 - relative yield of phosphorus) x unit yield of phosphorus absorption of above-ground part ÷ utilization rate of phosphorus fertilizer + target yield x unit yield of phosphorus absorption of grain x coefficient of phosphorus balance;

[0030] Wherein, the utilization rate of phosphorus fertilizer is calculated according to the seasonal utilization rate: 20% to 40% for winter rape, and 20% to 40% for medium rice; the coefficient of phosphorus balance determined according to the principle of nutrient balance is 0.1 to 1.0 for winter rape, and 0.1 to 1.0 for medium rice;

[0031] In order to take into account the apparent balance result of soil phosphorus, the coefficient of balance is proposed to maintain the gain and loss of soil phosphorus within the range of ±15% of the absorption of above-ground part phosphorus.

[0032] Amount of potassium application = target yield x (1 - relative yield of potassium) x unit yield of potassium absorption of above-ground part ÷ utilization rate of potassium fertilizer + target yield x unit potassium absorption of grain + target yield x unit potassium absorption of straw x coefficient of potassium balance;

[0033] Wherein, the utilization rate of potassium fertilizer is calculated according to the seasonal utilization rate: 30% to 70% for winter rape, and 30% to 70% for medium rice; the coefficient of potassium balance determined according to the principle of nutrient balance is 0.1 to 0.5 for winter rape, and 0.1 to 0.5 for medium rice;

[0034] In order to take into account the apparent balance result of soil potassium, the coefficient of balance is proposed to maintain the gain and loss of soil potassium within the range of ±15% of the absorption of above-ground part potassium.

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

[0036] The amount of nitrogen brought in by the straw of the previous crop = the amount of nitrogen absorbed by the straw of the previous crop x the release rate of nitrogen in the straw x the availability of nitrogen;

[0037] The amount of phosphorus brought in by the straw of the previous crop = the amount of phosphorus absorbed by the straw of the previous crop x the release rate of phosphorus in the straw x the availability of phosphorus;

[0038] The amount of potassium brought in by the straw of the previous crop = the amount of potassium absorbed by the straw of the previous crop x the release rate of potassium in the straw x the availability of potassium;

[0039] Wherein, the nutrient absorption of the straw of the previous crop = yield x unit yield of nutrient absorption of straw; the release rates of nitrogen, phosphorus and potassium in the straw of winter rape are 61.1%, 61.6% and 96.1% respectively, and the availability of nitrogen, phosphorus and potassium in the straw of winter rape for the medium rice season is 40%, 30% and 40% respectively;

[0040] The release rates of nitrogen, phosphorus and potassium in the straw of medium rice are 43.5%, 63.6% and 95.0% respectively, and the availability of nitrogen, phosphorus and potassium in the straw of medium rice for the winter rape season is 30%, 20% and 30% respectively;

[0041] (6) According to step (4) and step (5), the final fertilizer nitrogen, phosphorus and potassium application amounts of winter rape and middle rice are determined;

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

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

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

[0045] Preferably, the nitrogen, phosphorus and potassium in the winter rape special fertilizer are applied in several times, and are divided into winter rape base fertilizer special fertilizer, winter rape overwintering special fertilizer and winter rape budding special fertilizer; wherein, the winter rape base fertilizer special fertilizer accounts for 60% of the final nitrogen application amount, the winter rape overwintering special fertilizer accounts for 20% of the final nitrogen application amount, and the winter rape budding special fertilizer accounts for 20% of the final nitrogen application amount; the winter rape base fertilizer special fertilizer accounts for 100% of the final phosphorus application amount; the winter rape base fertilizer special fertilizer accounts for 50% of the final potassium application amount, the winter rape overwintering special fertilizer accounts for 20% of the final potassium application amount, and the winter rape budding special fertilizer accounts for 30% of the final potassium application amount;

[0046] The nitrogen, phosphorus and potassium in the middle rice special fertilizer are applied in several times, and are divided into middle rice base fertilizer special fertilizer, middle rice tillering special fertilizer and middle rice booting special fertilizer; wherein, the middle rice base fertilizer special fertilizer accounts for 40% of the final nitrogen application amount, the middle rice tillering special fertilizer accounts for 25% of the final nitrogen application amount, and the middle rice booting special fertilizer accounts for 35% of the final nitrogen application amount; the middle rice base fertilizer special fertilizer accounts for 100% of the final phosphorus application amount; the middle rice base fertilizer special fertilizer, the middle rice tillering special fertilizer and the middle rice booting special fertilizer each accounts for 1 / 3 of the final potassium application amount.

[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 nutrient brought in by stalks of previous crop, 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 nutrients of stalks of previous crop, but also gives the special fertilizer formula of main growth stages. The special fertilizer formula for crops in the winter rape-middle rice 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 the winter rape-middle rice rotation system under stalks returning to field in Example 1 of the present application. DETAILED DESCRIPTION

[0050] The following detailed description is presented to enable any person skilled in the art to make and use the application. Descriptions of specific embodiments are included for purposes of description and explanation, and not for limitation.

[0051] It should be noted that the present application does not describe in detail the conventional operation means in the art, and is not the focus of the present application.

[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. Each smaller range between any stated value or intermediate value in the stated range, and any other stated value or intermediate value in the stated range, is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All publications mentioned herein are incorporated by reference for the purposes of describing and disclosing the materials and methodologies that are described in the publication and which might be used in the practice or testing of the present application.

[0054] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended terms that are intended to mean "including but not limited to".

[0055] The schematic diagram of the fertilization method of the crop special fertilizer in the winter rape-rice rotation system with straw incorporated into the field in Example 1 of the present application is shown in Figure 1 .

[0056] Example 1

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

[0058] The pre-sowing soil test value is: organic matter 19.7 g / kg, hydrolyzable nitrogen 108 mg / kg, available phosphorus 14.5 mg / kg, and available potassium 120.0 mg / kg.

[0059] Step A2: Determine the soil nitrogen, phosphorus, and potassium nutrient supply level based on the results of the soil organic matter, available phosphorus, and available potassium tests. The specific relationship between the soil organic matter content and the soil nitrogen supply level is shown in Table 1. However, when the soil hydrolyzable nitrogen is ≥150 mg / kg, the organic matter test level "low" is upgraded to the test level "medium". When the hydrolyzable nitrogen is ≤100 mg / kg, the organic matter test level "high" is downgraded to the test level "medium".

[0060] The pre-sowing soil organic matter is 19.7 g / kg, which is between 10-30 g / kg, and is of medium level. No adjustment is needed for the soil nitrogen supply level, which is also of medium level. The available phosphorus is 14.5 mg / kg, which is between 10-25 mg / kg, and is of medium level. The available potassium is 120.0 mg / kg, which is between 80-150 mg / kg, and is of medium level.

[0061] The final determination of the soil nutrient test values of the recommended fertilization plot is that the soil nitrogen, phosphorus, and potassium supply levels are all of medium level.

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

[0063]

[0064] Step A3: Determine the target yield. Based on the farmer's customary fertilization measures, the winter rape yield is increased by 15%, and the medium rice yield is increased by 10%. Taking the farmer's customary yield of winter rape as 2.5 t / ha and medium rice as 8 t / ha as an example, the target yield is:

[0065] Winter rape: 2.5 + 2.5 x 15% = 2.875 t / ha;

[0066] Medium rice: 8 + 8 x 10% = 8.8 t / ha.

[0067] Step A4: Determine the soil nitrogen, phosphorus, and potassium nutrient supply level parameters:

[0068] Calculate the nitrogen, phosphorus, and potassium relative yields based on the yields of applying only two of nitrogen, phosphorus, and potassium fertilizers and full application of fertilizers.

[0069] Nitrogen relative yield = yield of applying only phosphorus and potassium ÷ yield of applying nitrogen, phosphorus, and potassium;

[0070] Phosphorus relative yield = yield of applying only nitrogen and potassium ÷ yield of applying nitrogen, phosphorus, and potassium;

[0071] Potassium relative yield = yield of applying only nitrogen and phosphorus ÷ yield of applying nitrogen, phosphorus, and potassium;

[0072] The winter rape has 2149, 2151, and 2151 data of nitrogen, phosphorus, and potassium relative yields, respectively.

[0073] There are 1387, 711 and 788 relative yield data of nitrogen, phosphorus and potassium in medium rice soil, respectively;

[0074] The 25th percentile, 50th percentile and 75th percentile of the relative yield of nitrogen, phosphorus and potassium are determined as the parameters of "low", "medium" and "high" levels of nitrogen, phosphorus and potassium supply;

[0075] The obtained nitrogen, phosphorus and potassium soil nutrient supply level parameters of winter rape and medium rice are shown in Table 2.

[0076] Table 2 Corresponding table of nitrogen, phosphorus and potassium soil nutrient supply level parameters of winter rape and medium rice

[0077]

[0078] By determining the soil nitrogen, phosphorus and potassium nutrient supply level through step A2, combined with the obtained supply level parameters in Table 2, the corresponding winter rape soil nitrogen, phosphorus and potassium level parameters are 0.582, 0.786 and 0.862, respectively; the corresponding medium rice soil nitrogen, phosphorus and potassium level parameters are 0.744, 0.917 and 0.909, respectively.

[0079] Step A5: Determining the nutrient demand per unit yield:

[0080] First, collect winter rape and medium rice field test data or arrange field test, which must include grain yield, straw yield and nitrogen, phosphorus and potassium nutrient uptake;

[0081] Further, the QUEFTS model is applied to simulate the quantitative relationship between grain yield and aboveground nutrient uptake;

[0082] Then, the aboveground nutrient demand per unit yield is obtained by using the target yield which can reach 80% of the potential yield as the final aboveground nutrient demand per unit yield;

[0083] The calculated aboveground nitrogen, phosphorus and potassium nutrient demand per unit yield of winter rape is 50.1, 12.7 and 51.9 kg / t, respectively; the aboveground nitrogen, phosphorus and potassium nutrient demand per unit yield of medium rice is 19.5, 3.5 and 23.8 kg / t, respectively;

[0084] Further, the QUEFTS model is applied to simulate the quantitative relationship between grain yield and grain nutrient uptake, and the grain nutrient demand per unit yield is calculated;

[0085] The calculated grain nitrogen, phosphorus and potassium nutrient demand per unit yield of winter rape is 28.3, 5.5 and 8.3 kg / t, respectively; the grain nitrogen, phosphorus and potassium nutrient demand per unit yield of medium rice is 12.3, 2.3 and 2.9 kg / t, respectively.

[0086] Step A6: Determine the unit yield of straw nutrient absorption:

[0087] Winter rape straw nitrogen absorption = 50.1-28.3 = 21.8 kg / t;

[0088] Winter rape straw nitrogen absorption = 12.7-5.5 = 7.2 kg / t;

[0089] Winter rape straw nitrogen absorption = 51.9-8.3 = 43.6 kg / t;

[0090] Medium rice straw nitrogen absorption = 19.5-12.3 = 7.2 kg / t;

[0091] Medium rice straw nitrogen absorption = 3.5-2.3 = 1.2 kg / t;

[0092] Medium rice straw nitrogen absorption = 23.8-2.9 = 20.9 kg / t;

[0093] Step A7: Determine the recommended amount of nitrogen, phosphorus and potassium nutrients:

[0094] Combined with the target yield of winter rape-medium rice, the nutrient requirement per unit yield, straw return amount, fertilizer utilization rate and nutrient balance coefficient to determine the fertilizer nutrient requirement.

[0095] Adjust the fertilizer recycling rate in the season, among them, the phosphorus and potassium recycling rates of winter rape are adjusted to 25% and 50% respectively; the phosphorus and potassium recycling rates of medium rice are adjusted to 30% and 50% respectively;

[0096] Determine the nutrient balance coefficient, among them, the phosphorus and potassium nutrient balance coefficients of winter rape seed are determined to be 0.1 and 0.3 respectively; the phosphorus and potassium nutrient balance coefficients of medium rice seed are determined to be 1.0 and 0.1 respectively;

[0097] Calculate the amount of nitrogen, phosphorus and potassium:

[0098] Winter rape:

[0099] According to a large number of field tests in the past, it is determined that the nitrogen agronomic efficiency calculation formula of winter rape in the main production area of winter rape-medium rice in the middle and lower reaches of the Yangtze River is a =-0.5561, b = 6.1658, c = 0.2039; medium rice:

[0100] The amount of nitrogen applied = (2.875 x (1-0.582) x 1000) ÷ [-0.5561 x (2.875 x (1-0.582) 2 + 6.1658 x 2.875 x (1-0.582) + 0.2039] = 176.5 kg / ha;

[0101] The amount of phosphorus applied = 2.875 x (1-0.786) x 12.7 ÷ 25% + 2.875 x 5.5 x 0.1 = 32.8 kg / ha;

[0102] The amount of potassium applied = 2.875 x (1-0.862) x 51.9 ÷ 50% + 2.875 x 8.3 + 2.875 x 43.6 x 0.3 = 102.7 kg / ha;

[0103] Medium rice:

[0104] According to a large number of field tests in the past, it is determined that the nitrogen agricultural efficiency calculation formula of medium rice in the main production area of winter rape-medium rice in the middle and lower reaches of the Yangtze River is a =-0.4096, b = 6.1548, c = 0.0725;

[0105] The amount of nitrogen applied = (8.8 x (1-0.744) x 1000) ÷ [-0.4096 x (8.8 x (1-0.744) 2 + 6.1548 x 8.8 x (1-0.744) + 0.0725] = 190.0 kg / ha;

[0106] The amount of phosphorus applied = 8.8 x (1-0.917) x 3.5 ÷ 30% + 8.8 x 2.3 = 28.8 kg / ha;

[0107] The amount of potassium applied = 8.8 x (1-0.909) x 23.8 ÷ 50% + 8.8 x 2.9 + 8.8 x 20.9 x 0.1 = 82.0 kg / ha.

[0108] Step A8: Determine the amount of nutrients brought in by the previous crop straw, where the winter rape previous crop is medium rice, and the farmer's yield is 8 t / ha, and the medium rice previous crop is winter rape, and the farmer's yield is 2.5 t / ha;

[0109] The nitrogen, phosphorus, and potassium nutrient release rates of winter rape straw in the medium rice planting season are 61.1%, 61.6%, and 96.1%, respectively, and the nitrogen, phosphorus, and potassium nutrient availability of winter rape straw for the medium rice season is 40%, 30%, and 40%, respectively;

[0110] The nitrogen, phosphorus, and potassium nutrient release rates of medium rice straw in the winter rape planting season are 43.5%, 63.6%, and 95.0%, respectively, and the nitrogen, phosphorus, and potassium nutrient availability of medium rice straw for the winter rape season is 30%, 20%, and 30%, respectively;

[0111] The amount of nutrients brought in by the previous crop medium rice straw before winter rape planting:

[0112] The amount of nitrogen brought in by the previous crop medium rice straw = 8 x 7.2 x 43.5% x 30% = 7.5 kg / ha;

[0113] The amount of phosphorus brought in by rice straw in the previous crop = 8 x 1.2 x 63.6% x 20% = 1.2 kg / ha;

[0114] The amount of potassium brought in by rice straw in the previous crop = 8 x 20.9 x 95.0% x 30% = 47.7 kg / ha;

[0115] The amount of nutrients brought in by winter rape straw in the previous crop before mid-season rice planting:

[0116] The amount of nitrogen brought in by winter rape straw in the previous crop = 2.5 x 21.8 x 61.1% x 40% = 13.3 kg / ha;

[0117] The amount of phosphorus brought in by winter rape straw in the previous crop = 2.5 x 7.2 x 61.6% x 30% = 3.3 kg / ha;

[0118] The amount of potassium brought in by winter rape straw in the previous crop = 2.5 x 43.6 x 96.1% x 40% = 41.9 kg / ha.

[0119] Step A9: Determine the final fertilizer N, P, and K amounts for the winter rape-mid-season rice rotation system:

[0120] Winter rape:

[0121] Final N application amount = 176.5 - 7.5 = 169.0 kg / ha;

[0122] Final P application amount = 32.8 - 1.2 = 31.6 kg / ha;

[0123] Final K application amount = 102.7 - 47.7 = 55.0 kg / ha;

[0124] Mid-season rice:

[0125] Final N application amount = 190.0 - 13.3 = 176.7 kg / ha;

[0126] Final P application amount = 28.8 - 3.3 = 25.5 kg / ha;

[0127] Final K application amount = 82.0 - 41.9 = 40.1 kg / ha.

[0128] Step A10: Determine the N, P2O5, and K2O ratios for special-purpose fertilizers for the main growth stages during the growth period of the winter rape-mid-season rice rotation under straw return:

[0129] Winter rape growth period fertilization stages are at the seeding period, overwintering period, and bolting period, corresponding to winter rape special-purpose fertilizers as base fertilizer special-purpose fertilizer, overwintering special-purpose fertilizer, and bolting special-purpose fertilizer; N is calculated according to the base and top-up ratio of 60%-20%-20%, P is all base fertilizer, and K is calculated according to the base and top-up ratio of 50%-20%-30%;

[0130] According to the final nitrogen, phosphorus, potassium application amount and nitrogen, phosphorus, potassium application mode of winter rape, the N, P, K application amount in base fertilizer special fertilizer is determined as 101.4, 31.6, 27.5 kg / ha, which is converted into N, P2O5, K2O as 101.4, 72.4, 33.1 kg / ha;

[0131] According to the final nitrogen, phosphorus, potassium application amount and nitrogen, phosphorus, potassium application mode of winter rape, the N, P, K application amount in overwintering special fertilizer is determined as 33.8, 0, 11 kg / ha, which is converted into N, P2O5, K2O as 33.8, 0, 13.3 kg / ha;

[0132] According to the final nitrogen, phosphorus, potassium application amount and nitrogen, phosphorus, potassium application mode of winter rape, the N, P, K application amount in overwintering special fertilizer is determined as 33.8, 0, 11 kg / ha, which is converted into N, P2O5, K2O as 33.8, 0, 13.3 kg / ha;

[0133] The main growth period of middle rice is respectively at the transplanting period, the tillering period and the booting period, and the corresponding middle rice special fertilizer includes base fertilizer special fertilizer, tillering special fertilizer and booting special fertilizer; N is according to the base and the ratio of 40%-25%-35%, P is all as base fertilizer, and K is according to one third respectively;

[0134] According to the final nitrogen, phosphorus, potassium application amount and nitrogen, phosphorus, potassium application mode of middle rice, the N, P, K application amount in base fertilizer special fertilizer is determined as 70.7, 25.5, 13.4 kg / ha, which is converted into N, P2O5, K2O as 70.7, 58.4, 16.1 kg / ha;

[0135] According to the final nitrogen, phosphorus, potassium application amount and nitrogen, phosphorus, potassium application mode of middle rice, the N, P, K application amount in base fertilizer special fertilizer is determined as 70.7, 25.5, 13.4 kg / ha, which is converted into N, P2O5, K2O as 70.7, 58.4, 16.1 kg / ha;

[0136] According to the final nitrogen, phosphorus, potassium application amount and nitrogen, phosphorus, potassium application mode of middle rice, the N, P, K application amount in base fertilizer special fertilizer is determined as 70.7, 25.5, 13.4 kg / ha, which is converted into N, P2O5, K2O as 70.7, 58.4, 16.1 kg / ha;

[0137] Finally, according to GB 15063-2001 standard, the total nutrient content of winter rape-rice special fertilizer and the corresponding N:P205:K20 grade were determined respectively.

[0138] In the main production area of winter rape-rice in the middle and lower reaches of the Yangtze River, the conventional fertilization and the optimized fertilization were set as the control, and both of the two fertilization scenarios were carried out under the condition of straw returning to field. The rationality of optimized fertilization under straw returning to field was verified. The verification parameters included yield, fertilizer amount, and nutrient recovery rate under different fertilization scenarios. The results are shown in Table 3.

[0139] Table 3

[0140]

[0141] Note: The fertilizer amount of optimized fertilization in Table 3 is the recommended amount, which takes into account the amount of straw nutrient brought in by the previous crop.

[0142] Table 3 shows the effect of different fertilization scenarios on the yield and nutrient recovery rate of winter rape and rice. The field test results show that compared with conventional fertilization, optimized fertilization reduces the amount of fertilizer, with a reduction of 17.6% and 15.8% in nitrogen application, 19.6% and 44.4% in phosphorus application, and 22.0% and 53.9% in potassium application for winter rape and rice, respectively. However, the yield increases by 7.4% and 7.2%, respectively. The nitrogen fertilizer recovery rate increases by 6.5 and 6.6 percentage points, the phosphorus fertilizer recovery rate increases by 7.2 and 3.5 percentage points, and the potassium fertilizer recovery rate increases by 20.2 and 48.0 percentage points, respectively.

[0143] The humus formed by the decomposition of straw can improve soil porosity and alleviate the problem of compaction caused by long-term flooding in rice fields. It also enhances the water retention capacity of rape fields. However, if the high carbon and nitrogen of straw are not combined with reasonable fertilizer application, it will lead to competition for nitrogen between microorganisms and crops, resulting in weak seedlings due to nitrogen deficiency. Straw returning to the field provides a carbon source for microorganisms, stimulates their activity, and accelerates nutrient transformation, especially for anaerobic microbial communities in rice soil. After returning the straw of the previous crop to the field, appropriate additional nitrogen fertilizer can be applied at sowing to adjust the carbon-nitrogen ratio of the soil and meet the nitrogen needs of crops and microorganisms. The combination of base fertilizer and special fertilizer for topdressing can ensure the supply of nitrogen throughout the crop growth period. The nutrients in the straw of rape and rice have strong complementarity, and after returning to the field, they can achieve efficient recycling of nutrients. The current optimized fertilization can significantly reduce the amount of fertilizer compared to the current farmer's conventional fertilization, and has a significant effect on yield and fertilizer utilization. At the same time, straw returning to the field plays an important role in improving soil structure, increasing soil organic matter content, and improving soil fertility. Straw returning to the field in the winter rape-rice rotation system is a key measure to achieve soil health, resource efficiency, and sustainable agricultural development, with both ecological and economic values.

[0144] The above-described embodiments are merely intended to describe the preferred modes of the present application, and are not intended to limit the scope of the present application. Various modifications and improvements of the present application made by those skilled in the art based on the above-described embodiments should fall within the scope of the present application defined by the claims.

Claims

1. A method for preparing fertilizers for crops in a winter rapeseed-mid-season rice rotation system with straw returned to the field, 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 ≥150mg / 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 winter rapeseed and mid-season rice 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 amount of fertilizer should be determined based on the target yield of winter rapeseed and mid-season rice, the nutrient requirement per unit yield, the amount of straw returned to the field, the fertilizer utilization rate, and the 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 in the current season: 20% to 40% for winter rapeseed and 20% to 40% for mid-season rice; the phosphorus balance coefficient determined based on the nutrient balance principle is 0.1 to 1.0 for winter rapeseed and 0.1 to 1.0 for mid-season rice; 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 potassium fertilizer utilization rate is calculated according to the utilization rate in the current season: 30% to 70% for winter rapeseed and 30% to 70% for mid-season rice; the potassium balance coefficient determined according to the nutrient balance principle is 0.1 to 0.5 for winter rapeseed and 0.1 to 0.5 for mid-season rice; (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 nutrient absorption of the previous crop straw = yield × nutrient absorption of straw per unit yield; the nitrogen, phosphorus, and potassium nutrient release rates of winter rapeseed straw are 61.1%, 61.6%, and 96.1%, respectively. The nitrogen, phosphorus, and potassium nutrient availability of winter rapeseed straw to the mid-season rice season is 40%, 30%, and 40%, respectively; The release rates of nitrogen, phosphorus and potassium nutrients from mid-season rice straw were 43.5%, 63.6% and 95.0% respectively, and the availability of nitrogen, phosphorus and potassium nutrients from mid-season rice straw to winter rapeseed was 30%, 20% and 30% respectively; (6) Determine the final nitrogen, phosphorus, and potassium fertilizer application rates for winter rapeseed and mid-season rice 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 fertilizers for crops in the winter rapeseed-mid-season rice rotation system under straw return to the field according to claim 1, characterized in that: The nitrogen, phosphorus and potassium in the special fertilizer for winter rapeseed are applied in stages, and are divided into special fertilizer for winter rapeseed base fertilizer, special fertilizer for winter rapeseed overwintering and special fertilizer for winter rapeseed bolting; wherein, the special fertilizer for winter rapeseed base fertilizer accounts for 60% of the final nitrogen application amount, the special fertilizer for winter rapeseed overwintering accounts for 20% of the final nitrogen application amount, and the special fertilizer for winter rapeseed bolting accounts for 20% of the final nitrogen application amount; the special fertilizer for winter rapeseed base fertilizer accounts for 100% of the final phosphorus application amount; the special fertilizer for winter rapeseed base fertilizer accounts for 50% of the final potassium application amount, the special fertilizer for winter rapeseed overwintering accounts for 20% of the final potassium application amount, and the special fertilizer for winter rapeseed bolting accounts for 30% of the final potassium application amount; The nitrogen, phosphorus and potassium in the special fertilizer for medium rice are applied in batches, and are divided into special fertilizer for medium rice base fertilizer, special fertilizer for medium rice tillering and special fertilizer for medium rice heading; among them, the special fertilizer for medium rice base fertilizer accounts for 40% of the final nitrogen application amount, the special fertilizer for medium rice tillering accounts for 25% of the final nitrogen application amount, and the special fertilizer for medium rice heading accounts for 35% of the final nitrogen application amount; the special fertilizer for medium rice base fertilizer accounts for 100% of the final phosphorus application amount; the special fertilizer for medium rice base fertilizer, special fertilizer for medium rice tillering and special fertilizer for medium rice heading each account for 1 / 3 of the final potassium application amount.

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