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

Abstract

The invention discloses a method for preparing a special fertilizer for winter wheat-middle-season rice crop rotation system crops under straw returning, and belongs to the technical field of wheat-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 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 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 wheat-middle-season rice crop rotation system crops under straw returning not only can improve the yield of crops, but also can improve the utilization efficiency of nutrients.

Description

Technical Field

[0001] The invention belongs to the technical field of wheat-rice rotation, and particularly relates to a method for allocating special fertilizers for crops in a winter wheat-mid-season rice rotation system under straw return. Background Art

[0002] As a byproduct of agricultural production, large quantities of straw are produced annually. Returning straw to fields is now a common practice, with significant positive effects on soil physical and chemical properties and crop yields. Returning straw to fields is a significant source of soil organic carbon, not only improving soil fertility and increasing crop yield, but also improving soil structure and increasing soil aggregate stability. As an organic matter, returning straw to fields provides microorganisms with high-carbon molecular compounds. The carbon in straw, decomposed by soil microorganisms, forms humus, ultimately increasing soil organic carbon and further improving soil fertility. Returning straw to fields also promotes the conversion of microaggregates into macroaggregates, increasing soil porosity and thereby enhancing soil water infiltration and retention. If straw is randomly piled or burned in fields, it can produce large amounts of greenhouse gases and smog, affecting air quality and even the urban environment. Therefore, returning straw to fields is of great significance for improving the environment and effectively utilizing crop resources.

[0003] After crop straw is returned to the fields, it slowly releases nutrients during the decomposition process, which not only balances soil pH but also increases the content of available nutrients in the soil, improves the structure of soil microbial communities, and enhances the soil microecological environment. However, the nutrients in straw cannot be directly absorbed and utilized by crops and must undergo microbial decomposition, which takes a long time. In addition, the nutrient release rate of straw varies in different growing environments, and the proportions of nitrogen, phosphorus, and potassium in different straws also vary. Therefore, in actual nutrient management, it is necessary to use different amounts of chemical fertilizers after returning straw to the fields in different crop rotation systems.

[0004] Long-term high-intensity planting will lead to a continuous decline in soil fertility. Excessive fertilization and water-land rotation will also lead to fertilizer loss and low fertilizer utilization rate. As an important support for the sustainable development of modern agriculture, chemical fertilizers play a significant role in improving crop yields, but they also face the problem of excessive application leading to resource waste and environmental pollution. Straw is rich in nitrogen, phosphorus and potassium elements and has a high potential to replace fertilizers. If this part of nutrients is fully utilized, it will further improve the efficiency of reducing the use of chemical fertilizers. Therefore, it is very necessary to formulate crop-specific fertilizers for the winter wheat-mid-season rice rotation system under the condition of straw return to the field to improve crop yield and fertilizer utilization efficiency. Summary of the Invention

[0005] The present invention aims to provide a method for formulating fertilizers specifically for crops in a winter wheat-mid-season rice rotation system using straw return. Specifically, by optimizing key parameters such as nutrient uptake, soil nutrient supply, and fertilizer utilization efficiency, while taking into account the nutrient intake and release rate of the previous crop straw, a method for calculating the nitrogen, phosphorus, and potassium nutrient requirements for fertilizers specifically for different growth stages in a winter wheat-mid-season rice rotation system is proposed. This method effectively improves crop yield and soil fertility in a winter wheat-mid-season rice rotation system using straw return, achieving reduced fertilizer application and increased efficiency. The method can provide technical support for fertilizer manufacturers in formulating fertilizers specifically for crops in this system.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a method for preparing fertilizers for crops in a winter wheat-mid-season rice rotation system with straw return to the field, comprising the following steps:

[0008] (1) Determine the soil nutrient supply level based on the soil nutrient test value before sowing:

[0009] 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;

[0010] 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 "low" is upgraded to the test level "medium"; when the hydrolyzable nitrogen is ≤100mg / kg, the organic matter test level "high" is downgraded to the test level "medium";

[0011] When the available phosphorus content is less than 10 mg / kg, the available phosphorus test level is "low", when the available phosphorus content is between 10 and 25 mg / kg, the available phosphorus test level is "medium", and when the available phosphorus content is greater than 25 mg / kg, the available phosphorus test level is "high". The "low", "medium" and "high" available phosphorus test levels correspond to the "low", "medium" and "high" soil phosphorus supply levels, respectively.

[0012] 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.

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

[0014] 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;

[0015] Relative nitrogen yield = yield of phosphorus and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined;

[0016] Relative phosphorus yield = yield of nitrogen and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined;

[0017] Relative potassium yield = yield of nitrogen and phosphorus alone ÷ yield of nitrogen, phosphorus and potassium combined;

[0018] N groups of experiments were conducted to obtain N nitrogen relative yields, N phosphorus relative yields, and N potassium relative yields; among them, the 25% quantile, 50% quantile, and 75% quantile of the N nitrogen relative yields were determined as parameters for the "low", "medium", and "high" levels of nitrogen supply; the 25% quantile, 50% quantile, and 75% quantile of the N phosphorus relative yields were determined as parameters for the "low", "medium", and "high" levels of phosphorus supply; and the 25% quantile, 50% quantile, and 75% quantile of the N potassium relative yields were determined as parameters for the "low", "medium", and "high" levels of potassium supply.

[0019] (3) Determine the nutrient requirements per unit yield of the winter wheat and mid-season rice rotation system:

[0020] 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.

[0021] Nitrogen absorption of straw per unit yield = nitrogen absorption of aboveground parts per unit yield - nitrogen absorption of grain per unit yield;

[0022] Phosphorus absorption of straw per unit yield = phosphorus absorption of aboveground part per unit yield - phosphorus absorption of grain per unit yield;

[0023] Potassium absorption of straw per unit yield = potassium absorption of aboveground part per unit yield - potassium absorption of grain per unit yield;

[0024] (4) Determine the amount of fertilizer:

[0025] The amount of fertilizer should be determined based on the target yield of winter wheat 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;

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

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

[0028] 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.

[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 yield of grain;

[0030] Among them, the utilization rate of phosphorus fertilizer is calculated according to the utilization rate in the current season: 10% to 30% for winter wheat and 10% to 30% for mid-season rice;

[0031] 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;

[0032] Among them, the utilization rate of potassium fertilizer is calculated according to the utilization rate of the season: 30% to 70% for winter wheat and 30% to 70% for mid-season rice; the potassium balance coefficient determined according to the principle of nutrient balance is 0.1 to 0.5 for winter wheat and 0.1 to 0.5 for mid-season rice;

[0033] In order to take into account the apparent balance of soil potassium, a balance coefficient was proposed to maintain the surplus or deficit of soil potassium within the range of ±15% of the aboveground potassium uptake.

[0034] (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;

[0035] Amount of nitrogen brought in by the previous crop straw = nitrogen absorption by the previous crop straw × straw nitrogen release rate × nitrogen effectiveness;

[0036] Phosphorus amount brought in by the previous crop straw = phosphorus absorption amount of the previous crop straw × phosphorus release rate of straw × phosphorus availability;

[0037] Potassium amount brought in by the previous crop straw = potassium absorption amount of the previous crop straw × straw potassium release rate × potassium effectiveness;

[0038] 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 wheat straw are 42.1%, 50.0%, and 98.0%, respectively. The nitrogen, phosphorus, and potassium nutrient availability of winter wheat straw to the mid-season rice season is 40%, 30%, and 40%, respectively;

[0039] 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 wheat was 30%, 20% and 30% respectively;

[0040] (6) Determine the final nitrogen, phosphorus, and potassium fertilizer application rates for winter wheat and mid-season rice based on steps (4) and (5);

[0041] Final nitrogen application amount = nitrogen application amount - nitrogen amount brought in by the previous crop straw;

[0042] Final phosphorus application amount = phosphorus application amount - phosphorus amount brought in by the previous crop straw;

[0043] Final potassium application amount = potassium application amount - potassium amount brought in by the previous crop straw.

[0044] Preferably, the nitrogen, phosphorus and potassium in the special fertilizer for winter wheat are applied in stages, and are divided into special fertilizer for winter wheat base fertilizer, special fertilizer for winter wheat greening and special fertilizer for winter wheat heading; wherein the special fertilizer for winter wheat base fertilizer accounts for 35% of the final nitrogen application amount, the special fertilizer for winter wheat greening accounts for 35% of the final nitrogen application amount, and the special fertilizer for winter wheat heading accounts for 30% of the final nitrogen application amount; the special fertilizer for winter wheat base fertilizer accounts for 100% of the final phosphorus application amount; the special fertilizer for winter wheat base fertilizer, the special fertilizer for winter wheat greening and the special fertilizer for winter wheat heading each account for 1 / 3 of the final potassium application amount;

[0045] 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.

[0046] The beneficial technical effects of the present invention are as follows:

[0047] The present invention truly reflects the nutrient supply level of the soil by combining soil nutrient testing with the yield-increasing effect of fertilization on crops; it optimizes farmers' customary fertilization while comprehensively considering the nutrients brought in by the straw of the previous crop, the nutrient release rate and nutrient effectiveness of the straw, the higher carbon-nitrogen ratio under straw return to the field, and the apparent potassium balance in the soil of the production area. Compared with traditional farmers' customary fertilization, the optimized recommended fertilizer formula of the present invention not only includes the nutrients of the straw of the previous crop, but also provides special fertilizer formulas for the main growth stages. The special fertilizer formula for crops in the winter wheat-mid-season rice rotation system under straw return to the field provided by the present invention can not only increase crop yields, but also improve nutrient utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of a method for allocating crop-specific fertilizers in a winter wheat-mid-season rice rotation system with straw return in Example 1 of the present invention. DETAILED DESCRIPTION

[0049] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0050] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0051] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0052] 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 the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0053] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0054] The schematic diagram of the method for dispensing special fertilizer for crops in the winter wheat-mid-season rice rotation system under straw return in Example 1 of the present invention is shown in FIG. Figure 1 .

[0055] Example 1

[0056] Step A1: Before planting, collect soil samples evenly distributed throughout the experimental plot. Collect soil samples from the topsoil layer (5-8 drill holes from 0-20 cm) and mix thoroughly. After sampling, air-dry the soil samples in a cool, shady place. After sieving, analyze them for organic matter, hydrolyzable nitrogen, available phosphorus, and readily available potassium to determine the soil nutrient status of the plots for recommended fertilization.

[0057] The soil test values ​​before sowing were: organic matter 23.5g / kg, hydrolyzable nitrogen 95.7mg / kg, available phosphorus 8.3mg / kg, and available potassium 103.5mg / kg.

[0058] Step A2: Based on step A1, the soil nitrogen, phosphorus, and potassium nutrient supply levels are determined; wherein, the soil nitrogen, phosphorus, and potassium nutrient supply levels are related to the test results of organic matter, available phosphorus, and available potassium in the soil. The specific relationship is shown in Table 1. In Table 1, the organic matter content corresponds to the soil nitrogen supply level. However, when the soil hydrolyzable nitrogen is ≥180 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";

[0059] Before sowing, the soil organic matter content was 13.5 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 8.3 mg / kg, which was less than 10 mg / kg, and was considered low. The available potassium content was 103.5 mg / kg, which was between 80 and 150 mg / kg, and was considered medium.

[0060] It was finally determined that the soil nitrogen and potassium supply levels corresponding to the soil nutrient test values ​​of the recommended fertilization plots were both medium; the phosphorus supply level was low.

[0061] Table 1 Soil nitrogen, phosphorus and potassium nutrient supply levels

[0062]

[0063] Step A3: Determine the target yield. Based on the farmer's customary fertilization yield, increase the yield of winter wheat and mid-season rice by 10%. For example, if the farmer's customary yield of winter wheat is 6 t / ha and mid-season rice is 9 t / ha, the target yield is:

[0064] Winter wheat: 6+6×10%=6.6t / ha;

[0065] Medium rice: 9+9×10%=9.9t / ha.

[0066] Step A4: Determine the soil nitrogen, phosphorus and potassium nutrient supply level parameters:

[0067] 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;

[0068] Relative nitrogen yield = yield of phosphorus and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined;

[0069] Relative phosphorus yield = yield of nitrogen and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined;

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

[0071] There are 692, 347, and 490 data on relative nitrogen, phosphorus, and potassium yields for winter wheat, respectively;

[0072] There are 1387, 711, and 788 data on the relative yields of soil nitrogen, phosphorus, and potassium in mid-season rice, respectively;

[0073] 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;

[0074] The obtained nitrogen, phosphorus and potassium soil nutrient supply level parameters for winter wheat and mid-season rice are shown in Table 2.

[0075] Table 2 Corresponding parameters of nitrogen, phosphorus and potassium soil nutrient supply levels for winter wheat and mid-season rice

[0076]

[0077] The soil nitrogen, phosphorus, and potassium nutrient supply levels were determined through step A2. Combined with the supply level parameters obtained in Table 2, the corresponding soil nitrogen, phosphorus, and potassium level parameters for winter wheat were 0.587, 0.795, and 0.900, respectively; the corresponding soil nitrogen, phosphorus, and potassium level parameters for mid-season rice were 0.744, 0.859, and 0.909, respectively.

[0078] Step A5: Determine nutrient requirements per unit of production:

[0079] First, collect field trial data on winter wheat and mid-season rice or arrange field trials. The data must include grain yield, straw yield, and nitrogen, phosphorus, and potassium nutrient absorption;

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

[0081] Then, the target yield can reach 80% of the potential yield to obtain the aboveground nutrient requirement per unit yield as the final aboveground nutrient requirement per unit yield;

[0082] The aboveground nitrogen, phosphorus, and potassium nutrient requirements per unit yield of winter wheat were calculated to be 22.9, 4.3, and 17.9 kg / t, respectively; the aboveground nitrogen, phosphorus, and potassium nutrient requirements per unit yield of mid-season rice were calculated to be 19.5, 3.5, and 23.8 kg / t, respectively.

[0083] Furthermore, the QUEFTS model was applied to simulate the quantitative relationship between grain yield and grain nutrient absorption, and the grain nutrient requirement per unit yield was calculated;

[0084] The calculation shows that the nitrogen, phosphorus and potassium nutrient requirements per unit yield of winter wheat are 17.3, 2.9 and 3.9 kg / t respectively; the nitrogen, phosphorus and potassium nutrient requirements per unit yield of mid-season rice are 12.3, 2.3 and 2.9 kg / t respectively.

[0085] Step A6: Determine the nutrient absorption per unit of straw yield:

[0086] Winter wheat straw nitrogen absorption = 22.9-17.3 = 5.6 kg / t;

[0087] Winter wheat straw nitrogen absorption = 4.3-2.9 = 1.4 kg / t;

[0088] Winter wheat straw nitrogen absorption = 17.9-3.9 = 14.0 kg / t;

[0089] Nitrogen absorption of medium rice straw = 19.5-12.3 = 7.2 kg / t;

[0090] Nitrogen absorption of medium rice straw = 3.5-2.3 = 1.2 kg / t;

[0091] Nitrogen absorption of medium rice straw = 23.8-2.9 = 20.9 kg / t.

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

[0093] The fertilizer nutrient requirement is determined based on the target yield of winter wheat 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.

[0094] Adjust the seasonal fertilizer recovery rate. For winter wheat, the phosphorus and potassium recovery rates are adjusted to 30% and 40% respectively; for mid-season rice, the phosphorus and potassium recovery rates are adjusted to 30% and 50% respectively.

[0095] Determine the nutrient balance coefficient, where the potassium nutrient balance coefficient of winter wheat straw is determined to be 0.3; the potassium nutrient balance coefficient of mid-season rice straw is determined to be 0.1;

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

[0097] Winter wheat:

[0098] Based on a large number of previous field experiments, the nitrogen agronomic efficiency calculation formula for winter wheat in the main winter wheat and mid-season rice producing areas in the Yangtze River Basin was determined to be a=-0.4061,b=6.7678,c=0.3494;

[0099] Nitrogen application rate = (6.6 × (1-0.587) × 1000) ÷ [-0.4061 × (6.6 × (1-0.587)) 2 +6.7678×6.6×(1-0.587)+0.3494]=172.7kg / ha;

[0100] Phosphorus application rate = 6.6 × (1-0.795) × 4.3 ÷ 30% + 6.6 × 2.9 = 38.5 kg / ha;

[0101] Potassium application rate = 6.6 × (1-0.900) × 17.9 ÷ 40% + 6.6 × 3.9 + 6.6 × 14.0 × 0.3 = 83.0 kg / ha;

[0102] Medium rice:

[0103] Based on a large number of previous field experiments, the nitrogen agronomic efficiency calculation formula for mid-season rice in the main winter wheat and mid-season rice producing areas in the Yangtze River Basin was determined to be a = -0.4096, b = 6.1548, and c = 0.0725;

[0104] Nitrogen application rate = (9.9 × (1-0.744) × 1000) ÷ [-0.4096 × (9.9 × (1-0.744)) 2 +6.1548×9.9×(1-0.744)+0.0725]=194.4kg / ha;

[0105] Phosphorus application rate = 9.9 × (1 - 0.859) × 3.5 ÷ 30% + 9.9 × 2.3 = 39.1 kg / ha;

[0106] Potassium application rate = 9.9×(1-0.909)×23.8÷50%+9.9×2.9+9.9×20.9×0.1=92.3 kg / ha.

[0107] Step A8: Determine the amount of nutrients introduced by the previous crop straw, where the previous crop of winter wheat is mid-season rice, and the farmer's yield is 9 t / ha; the previous crop of mid-season rice is winter wheat, and the farmer's yield is 6 t / ha;

[0108] The release rates of nitrogen, phosphorus and potassium nutrients from winter wheat straw were 42.1%, 50.0% and 98.0% respectively, and the availability of nitrogen, phosphorus and potassium nutrients from winter wheat straw to mid-season rice was 40%, 30% and 40% respectively.

[0109] 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 wheat was 30%, 20% and 30% respectively;

[0110] Nutrient content of rice straw before winter wheat planting:

[0111] Nitrogen introduced from rice straw of the previous crop = 9 × 7.2 × 43.5% × 30% = 8.5 kg / ha;

[0112] Phosphorus introduced from rice straw in the previous crop = 9 × 1.2 × 63.6% × 20% = 1.4 kg / ha;

[0113] Potassium content from rice straw of the previous crop = 9 × 20.9 × 95.0% × 30% = 53.6 kg / ha;

[0114] Amount of nutrients brought into the straw of winter wheat, the previous crop during the mid-season rice planting season:

[0115] Nitrogen introduced from the previous crop winter wheat straw = 6 × 5.6 × 42.1% × 40% = 5.7 kg / ha;

[0116] Phosphorus introduced from the previous crop winter wheat straw = 6 × 1.4 × 50.0% × 30% = 1.3 kg / ha;

[0117] The amount of potassium brought in by the previous crop winter wheat straw = 6×14.0×98.0%×40%=32.9 kg / ha.

[0118] Step A9: Determine the final fertilizer NPK dosage for the winter wheat-mid-season rice rotation system:

[0119] Winter wheat:

[0120] Final nitrogen application rate = 172.7-8.5 = 164.2 kg / ha;

[0121] Final phosphorus application rate = 38.5-1.4 = 37.1 kg / ha;

[0122] Final potassium application rate = 83.0-53.6 = 29.4 kg / ha;

[0123] Medium rice:

[0124] Final nitrogen application rate = 194.4 - 5.7 = 188.7 kg / ha;

[0125] Final phosphorus application rate = 39.1-1.3 = 37.8 kg / ha;

[0126] Final potassium application rate = 92.3-32.9 = 59.4 kg / ha.

[0127] Step A10: Determine the specific fertilizer N, P2O5, and K2O ratios for the main growth stages of the winter wheat-mid-season rice rotation under straw return:

[0128] The fertilization stages during the growth period of winter wheat are the sowing period, the greening period, and the heading period. The corresponding special fertilizers for winter wheat are base fertilizer, greening fertilizer, and heading fertilizer. The nitrogen fertilizer should be used as a base fertilizer at a ratio of 35%-35%-30%, all phosphorus should be used as a base fertilizer, and potassium fertilizer should be calculated at one-third each.

[0129] According to the final nitrogen, phosphorus and potassium application rates and application methods of winter wheat, the application rates of N, P and K in the base fertilizer were determined to be 57.5, 37.1 and 9.8 kg / ha respectively, which were converted to N, P2O5 and K2O, 57.5, 37.1×2.292 and 27.5×1.205, i.e. 57.5, 85.0 and 11.8 kg / ha respectively;

[0130] According to the final nitrogen, phosphorus and potassium application rates and application methods of winter wheat, the application rates of N, P and K in the greening fertilizer were determined to be 57.5, 0 and 9.8 kg / ha respectively, which were converted to N, P2O5 and K2O as 57.5, 0 and 9.8×1.205, i.e. 57.5, 0 and 11.8 kg / ha respectively;

[0131] According to the final nitrogen, phosphorus and potassium application rates and application methods of winter wheat, the application rates of N, P and K in the special fertilizer for heading were determined to be 49.3, 0 and 9.8 kg / ha respectively, which were converted to N, P2O5 and K2O as 49.3, 0 and 9.8×1.205, i.e. 49.3, 0 and 11.8 kg / ha respectively;

[0132] The main fertilization stages during the growth period of mid-season rice are the transplanting stage, the tillering stage, and the heading stage. The corresponding special fertilizers for mid-season rice include base fertilizer, tillering fertilizer, and heading fertilizer. The nitrogen should be used at a base-topdressing ratio of 40%-25%-35%, all phosphorus should be used as base fertilizer, and potassium should be calculated at one-third each.

[0133] According to the final nitrogen, phosphorus and potassium application rates and application methods of mid-season rice, the application rates of N, P and K in the base fertilizer were determined to be 75.5, 37.8 and 19.8 kg / ha respectively, which were converted to 75.5, 37.8×2.292 and 19.8×1.205 for N, P2O5 and K2O, i.e. 75.5, 86.6 and 23.8 kg / ha respectively;

[0134] According to the final nitrogen, phosphorus and potassium application rates and application methods of mid-season rice, the application rates of N, P and K in the tillering fertilizer were determined to be 47.2, 0 and 19.8 kg / ha respectively, which were converted to N, P2O5 and K2O as 47.2, 0 and 19.8×1.205, i.e. 47.2, 0 and 23.8 kg / ha respectively;

[0135] According to the final nitrogen, phosphorus and potassium application rates and application methods of mid-season rice, the application rates of N, P and K in the special fertilizer for heading were determined to be 66.0, 0 and 19.8 kg / ha respectively, which were converted into 66.0, 0 and 19.8×1.205 for N, P2O5 and K2O, i.e. 66.0, 0 and 23.8 kg / ha respectively;

[0136] Finally, the total nutrient content and corresponding N:P2O5:K2O grade of winter wheat-mid-season rice special fertilizer were determined according to GB 15063-2001 standard.

[0137] In the main winter wheat and mid-season rice producing areas of the Yangtze River Basin, two fertilization scenarios—conventional fertilization and optimized fertilization—were established, using conventional fertilization as a control. Both scenarios were conducted under straw return conditions to verify the rationality of optimized fertilizer allocation under straw return. The validation parameters included yield, fertilizer application rate, and nitrogen, phosphorus, and potassium nutrient recovery rates under different fertilization scenarios. The results are shown in Table 3.

[0138] Table 3

[0139]

[0140] Note: The fertilizer rates for optimized fertilization in Table 3 are recommended rates, taking into account the nutrient input from the previous crop straw.

[0141] Table 3 shows the effects of different fertilization scenarios on winter wheat and mid-season rice yield and nutrient recovery. Field test results showed that, compared with conventional fertilization, optimized fertilization reduced fertilizer application rates: nitrogen application rates for winter wheat and mid-season rice were reduced by 25.5% and 16.0%, phosphorus application rates were reduced by 19.0% and 22.3%, and potassium application rates were reduced by 70.8% and 42.9%, respectively. However, yields increased by 7.0% and 4.6%, respectively. Nitrogen recovery rates increased by 14.9 and 14.2 percentage points, phosphorus recovery rates increased by 12.9 and 13.3 percentage points, and potassium recovery rates increased by 27.7 and 26.9 percentage points, respectively.

[0142] After returning previous crop straw to the field, the nutrients in the straw cannot be directly absorbed and utilized by crops and must undergo microbial decomposition. The ideal carbon-to-nitrogen ratio for microbial decomposition is typically 25:1, but the carbon-to-nitrogen ratio in straw is consistently above 80:1. If the soil nitrogen supply is insufficient, microorganisms and crops will compete for nitrogen, resulting in nitrogen deficiency and weak seedlings. Applying an appropriate amount of nitrogen fertilizer at sowing after returning previous crop straw can adjust the soil carbon-to-nitrogen ratio to meet the nitrogen needs of both crops and microorganisms. Combining basal fertilizer with topdressing with specialized fertilizers ensures a nitrogen supply throughout the crop's growth period. Current optimized fertilization practices can significantly reduce fertilizer application rates compared to current farmer practices. By considering the effectiveness of nutrients introduced from previous crop straw for current crop production, fertilizer application rates can be further reduced, significantly improving both yield and fertilizer utilization efficiency. Furthermore, the role of returning straw to the field in improving soil structure, increasing soil organic matter content, and enhancing soil fertility cannot be underestimated. Therefore, returning straw to the fields in combination with optimized fertilizers can reduce the amount of fertilizer applied and the environmental pollution caused by straw burning, thus achieving green and sustainable agricultural development.

[0143] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing special fertilizers for crops in a winter wheat-mid-season rice rotation system under straw return 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 ≥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 winter wheat 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 wheat 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 yield of grain; Among them, the utilization rate of phosphorus fertilizer is calculated according to the utilization rate in the current season: 10% to 30% for winter wheat and 10% to 30% 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 utilization rate of potassium fertilizer is calculated according to the utilization rate of the season: 30% to 70% for winter wheat and 30% to 70% for mid-season rice; the potassium balance coefficient determined according to the principle of nutrient balance is 0.1 to 0.5 for winter wheat 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 wheat straw are 42.1%, 50.0%, and 98.0%, respectively. The nitrogen, phosphorus, and potassium nutrient availability of winter wheat 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 wheat was 30%, 20% and 30% respectively; (6) Determine the final nitrogen, phosphorus, and potassium fertilizer application rates for winter wheat 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 special fertilizers for crops in the winter wheat-mid-season rice rotation system under straw return to field according to claim 1, characterized in that: The nitrogen, phosphorus and potassium in the special fertilizer for winter wheat are applied in stages, and are divided into special fertilizer for winter wheat base fertilizer, special fertilizer for winter wheat greening and special fertilizer for winter wheat heading; among them, the special fertilizer for winter wheat base fertilizer accounts for 35% of the final nitrogen application amount, the special fertilizer for winter wheat greening accounts for 35% of the final nitrogen application amount, and the special fertilizer for winter wheat heading accounts for 30% of the final nitrogen application amount; the special fertilizer for winter wheat base fertilizer accounts for 100% of the final phosphorus application amount; the special fertilizer for winter wheat base fertilizer, special fertilizer for winter wheat greening and special fertilizer for winter wheat heading each account for 1 / 3 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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