Fertilizer preparation method of special fertilizer for next season of rice crops after straw returning to field

Abstract

The invention discloses a method for preparing a special fertilizer for next season rice crops after straw returning, and belongs to the technical field of rice planting. 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 crop fertilizer for the next-season rice planting system for 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 rice planting, and in particular relates to a method for preparing special fertilizer for the next rice crop after returning straw to the field. 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 thus 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. However, in production, straw is often randomly piled or burned in fields, generating significant amounts of greenhouse gases and smog, impacting 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] Straw contains a large amount of nitrogen, phosphorus and potassium, and is a valuable resource. After crop straw is returned to the field, it can slowly release nutrients during the decomposition process, which not only balances the pH of the soil, but also increases the content of available nutrients in the soil, improves the structure of the soil microbial community, and enhances the soil microecological environment. However, the nutrients in straw cannot be directly absorbed and utilized by crops and must be decomposed by microorganisms, which takes a long time. In addition, the nutrient release rate of straw varies in different growth environments, and the proportion of nitrogen, phosphorus and potassium in different straws also varies. Therefore, in the actual nutrient management process, it is very necessary to use different amounts of chemical fertilizers after returning straw to the field in different crop rotation systems.

[0004] During rice cultivation, long-term, high-intensity cultivation coupled with inappropriate nutrient management practices leads to a continuous decrease in soil organic matter, a decline in soil quality, accelerated soil acidification, and increased greenhouse gas emissions. Fertilizers, as a key support for the sustainable development of modern agriculture, significantly contribute to crop yields, but they also face the problem of excessive application, leading to resource waste and environmental pollution. As rice yields continue to rise, large quantities of straw are produced. Due to its slow decomposition, farmers often resort to burning it, which has a significant negative impact on the environment. Straw, rich in nitrogen, phosphorus, and potassium, has a high potential to replace fertilizers. Fully utilizing this nutrient content can further reduce the use of chemical fertilizers and increase their efficiency. However, when combining straw return with fertilization, it is important to note that the nutrient content and nutrient release rate of straw will affect the amount of chemical fertilizer applied. This is the fundamental reason why fertilizers specifically formulated for single-season rice cultivation systems must be selected based on straw return. Summary of the Invention

[0005] The present invention aims to provide a method for formulating fertilizer specifically for the next rice crop season after 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 specific fertilizers at different growth stages in a single-season rice cropping system is proposed. This method effectively improves crop yield and soil fertility in single-season rice cropping systems by returning straw to the field, achieving reduced fertilizer application and increased efficiency. It can provide technical support for fertilizer manufacturers in formulating specific fertilizers for single-season rice cropping systems.

[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 fertilizer specifically for the next rice crop after returning straw 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 requirement per unit yield of a single-season rice planting system:

[0020] The relationship between grain yield and aboveground nutrient absorption of crops in different cropping systems, as well as the relationship between grain yield and grain nutrient absorption, was simulated using the QUEFTS model. The aboveground nutrient absorption per unit yield and the 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 part 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 rice yield, nutrient requirement per unit yield, amount of straw returned to the field, fertilizer utilization rate, and 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 grain yield × phosphorus balance coefficient;

[0030] Among them, the utilization rate of phosphorus fertilizer is calculated according to the utilization rate of the season, which is 10% to 30%; the phosphorus balance coefficient determined according to the nutrient balance principle is 0.5 to 1.0;

[0031] In order to take into account the apparent balance of soil phosphorus, a balance coefficient was proposed to maintain the soil phosphorus surplus or deficit within the range of ±15% of aboveground phosphorus uptake.

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

[0033] Among them, the utilization rate of potassium fertilizer is calculated according to the utilization rate of the season, which is 30% to 70%; the potassium balance coefficient determined according to the nutrient balance principle is 0.1 to 0.5;

[0034] 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.

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

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

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

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

[0039] Among them, the nutrient absorption of the previous crop straw = yield × nutrient absorption of straw per unit yield; the nitrogen, phosphorus and potassium nutrient release rates of rice straw in a single season are 55.3%, 62.7% and 83.1% respectively, and the effectiveness is 30%, 20% and 30% respectively;

[0040] (6) determining the final application amounts of nitrogen, phosphorus, and potassium fertilizers for a rice crop according to 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 single-season rice are applied in batches, and are divided into special fertilizer for base fertilizer, special fertilizer for tillering and special fertilizer for heading; wherein, the special fertilizer for base fertilizer accounts for 40% of the final nitrogen application amount, the special fertilizer for tillering accounts for 25% of the final nitrogen application amount, and the special fertilizer for heading accounts for 35% of the final nitrogen application amount; the special fertilizer for base fertilizer accounts for 100% of the final phosphorus application amount; and the special fertilizer for base fertilizer, special fertilizer for tillering and special fertilizer for heading each account for 1 / 3 of the final potassium application amount.

[0045] The beneficial technical effects of the present invention are as follows:

[0046] 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 balance of phosphorus and potassium 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 rice planting system after straw return to the field provided by the present invention can not only increase crop yields, but also improve the utilization efficiency of nutrients. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of a method for preparing crop-specific fertilizers in a rice planting system for returning straw to the field in the next season in Example 1 of the present invention. DETAILED DESCRIPTION

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0053] The schematic diagram of the method for preparing special fertilizer for crops in the rice planting system of returning straw to the field in the next season in Example 1 of the present invention is shown in FIG. Figure 1 .

[0054] Example 1

[0055] 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.

[0056] The soil test values ​​before sowing were: organic matter 29.0g / kg, hydrolyzable nitrogen 135.5mg / kg, available phosphorus 33.9mg / kg, and available potassium 163.6mg / kg.

[0057] 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";

[0058] Before sowing, the soil organic matter content was 29.0 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 33.9 mg / kg, which was greater than 25 mg / kg, and was considered high. The available potassium content was 163.6 mg / kg, which was greater than 150 mg / kg, and was considered high.

[0059] It was finally determined that the soil nitrogen supply level corresponding to the soil nutrient test values ​​of the recommended fertilization plots was medium, and the soil phosphorus and potassium supply levels were both high.

[0060] Table 1 Soil nitrogen, phosphorus and potassium nutrient supply levels

[0061]

[0062] Step A3: Determine target yield:

[0063] Based on the yield of farmers' customary fertilization measures, increase it by 10%. Taking farmers' customary yield of 9t / ha as an example, the target yield is: 9+9×10%=9.9t / ha.

[0064] Step A4: Determine soil nitrogen, phosphorus, and potassium nutrient supply level parameters:

[0065] 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;

[0066] Relative nitrogen yield = yield of phosphorus and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined;

[0067] Relative phosphorus yield = yield of nitrogen and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined;

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

[0069] There are 477, 357, and 398 data on the relative yields of nitrogen, phosphorus, and potassium for single-season rice, respectively;

[0070] 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;

[0071] The obtained soil nutrient supply level parameters of nitrogen, phosphorus and potassium for single-season rice are shown in Table 2.

[0072] Table 2 Corresponding parameters of nitrogen, phosphorus and potassium soil nutrient supply levels for single-season rice

[0073]

[0074]

[0075] The soil nitrogen, phosphorus, and potassium nutrient supply levels are determined through step A2. Combined with the supply level parameters obtained in Table 2, the corresponding soil nitrogen, phosphorus, and potassium level parameters for single-season rice are 0.674, 0.951, and 0.944, respectively.

[0076] Step A5: Determine nutrient requirements per unit of production:

[0077] First, collect data from a rice field trial or arrange a field trial. The data must include grain yield, straw yield, and nitrogen, phosphorus, and potassium nutrient absorption;

[0078] Furthermore, the QUEFTS model was applied to simulate the quantitative relationship between grain yield and aboveground nutrient uptake respectively;

[0079] 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;

[0080] The calculated aboveground nitrogen, phosphorus, and potassium nutrient requirements per unit yield of one-season rice are 15.6, 3.9, and 15.6 kg / t, respectively;

[0081] 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;

[0082] The calculated nutrient requirements of nitrogen, phosphorus and potassium per unit yield of one-season rice grain are 9.5, 2.4 and 3.0 kg / t respectively.

[0083] Step A6: Determine the nutrient absorption per unit of straw yield:

[0084] Nitrogen absorption of rice straw in one season = 15.6-9.5 = 6.1 kg / t;

[0085] Nitrogen absorption of rice straw in one season = 3.9-2.4 = 1.5 kg / t;

[0086] The nitrogen absorption of rice straw in one season = 15.6-3.0 = 12.6 kg / t.

[0087] Step A7: Determine the recommended amounts of nitrogen, phosphorus, and potassium:

[0088] The fertilizer nutrient requirement is determined based on the target yield of one rice season, the nutrient requirement per unit yield, the amount of straw returned to the field, the fertilizer utilization rate, and the nutrient balance coefficient;

[0089] Adjust the seasonal fertilizer recycling rate to 30% for phosphorus and 50% for potassium;

[0090] Determine the nutrient balance coefficients, and the phosphorus and straw potassium nutrient balance coefficients are determined to be 1.0 and 0.2 respectively;

[0091] Calculate the amount of nitrogen, phosphorus and potassium:

[0092] Based on a large number of previous field experiments, the nitrogen agronomic efficiency calculation formula for rice in the main single-season rice producing areas of Northeast China is determined to be a=-0.4194,b=7.4719,c=-0.9699;

[0093] Nitrogen application rate = (9.9 × (1-0.674) × 1000) ÷ [-0.4194 × (9.9 × (1-0.674)) 2+7.4719×9.9×(1-0.674)-0.9699]=171.9kg / ha;

[0094] Phosphorus application rate = 9.9 × (1 - 0.951) × 3.9 ÷ 30% + 9.9 × 2.4 × 1.0 = 30.1 kg / ha;

[0095] Potassium application rate = 9.9×(1-0.944)×15.6÷50%+9.9×3.0+9.9×12.6×0.2=71.9 kg / ha.

[0096] Step A8: Determine the amount of nutrients introduced by the straw of the previous crop, where the previous crop is still single-season rice and the farmer's yield is 9 t / ha;

[0097] The release rates of nitrogen, phosphorus and potassium nutrients from rice straw in one season were 55.3%, 62.7% and 83.1% respectively, and their availability was 30%, 20% and 30% respectively;

[0098] Amount of nutrients brought in by the previous rice straw:

[0099] Nitrogen content from the previous rice straw = 9 × 6.1 × 55.3% × 30% = 9.1 kg / ha;

[0100] Phosphorus introduced from the previous rice straw = 9 × 1.5 × 62.7% × 20% = 1.7 kg / ha;

[0101] The amount of potassium brought in by the previous rice straw = 9 × 12.6 × 83.1% × 30% = 28.3 kg / ha.

[0102] Step A9: Determine the final fertilizer NPK dosage for the single-season rice cropping system:

[0103] Final nitrogen application rate = 171.9 - 9.1 = 162.8 kg / ha;

[0104] Final phosphorus application rate = 30.1-1.7 = 28.4 kg / ha;

[0105] Final potassium application rate = 71.9-28.3 = 43.6 kg / ha.

[0106] Step A10: Determine the ratio of N, P2O5, and K2O for the main growth stages of the next rice crop during the straw return period:

[0107] The main fertilization stages during the rice growth period are transplanting, tillering, and heading stages. The corresponding special fertilizers for one rice season include base fertilizer, tillering fertilizer, and heading fertilizer. The nitrogen fertilizer should be applied at a base-topdressing ratio of 40%-25%-35%, all phosphorus should be used as base fertilizer, and potassium fertilizer should be calculated at one-third each.

[0108] According to the final nitrogen, phosphorus and potassium application rates and application methods of one-season rice, the application rates of N, P and K in the base fertilizer were determined to be 65.1, 28.4 and 14.5 kg / ha respectively, which were converted to N, P2O5 and K2O as 65.1, 28.4×2.292 and 14.5×1.205, i.e. 65.1, 65.0 and 17.5 kg / ha respectively;

[0109] According to the final nitrogen, phosphorus and potassium application rates and application methods of single-season rice, the application rates of N, P and K in tillering fertilizer were determined to be 40.7, 0 and 14.5 kg / ha respectively, which were converted to N, P2O5 and K2O as 40.7, 0 and 14.5×1.205, i.e. 40.7, 0 and 17.5 kg / ha respectively;

[0110] According to the final nitrogen, phosphorus and potassium application rates and application methods of single-season rice, the application rates of N, P and K in the special fertilizer for heading were determined to be 57.0, 0 and 14.5 kg / ha respectively, which were converted to N, P2O5 and K2O as 57.0, 0 and 14.5×1.205, i.e. 57.0, 0 and 17.5 kg / ha respectively;

[0111] Finally, the total nutrient content and corresponding N:P2O5:K2O grade of special fertilizer for single-season rice were determined according to GB 15063-2001 standard.

[0112] In the main single-season rice-producing region of Northeast China, 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.

[0113] Table 3

[0114]

[0115] Note: The fertilizer rates for optimized fertilization in Table 3 are recommended rates, taking into account the nutrient input from the previous crop straw.

[0116] Table 3 shows the effects of different fertilization scenarios on single-season rice yield and nutrient recovery. Field trial results showed that compared with conventional fertilization, optimized fertilization reduced fertilizer application rates—nitrogen by 20.1%, phosphorus by 30.1%, and potassium by 39.8%—but yield increased by 11.6%, while nitrogen recovery increased by 18.0 percentage points, phosphorus recovery by 14.3 percentage points, and potassium recovery by 25.4 percentage points.

[0117] 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 appropriate amounts of nitrogen fertilizer at transplanting 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.

[0118] 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 ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for preparing special fertilizer for the next rice crop after returning straw 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 requirement per unit yield of a single-season rice planting system: The relationship between grain yield and aboveground nutrient absorption of crops in different cropping systems, as well as the relationship between grain yield and grain nutrient absorption, was simulated using the QUEFTS model. The aboveground nutrient absorption per unit yield and the 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 rice yield, nutrient requirement per unit yield, amount of straw returned to the field, fertilizer utilization rate, and nutrient balance coefficient; Nitrogen application rate = target yield × (1-nitrogen supply level parameter) ÷ nitrogen agronomic efficiency; Nitrogen agronomic efficiency = a × (target yield × (1-nitrogen supply level parameter)) 2 + b × target yield × (1-nitrogen supply level parameter) + c; Where a, b, and c are constant terms. Based on a large number of previous field experiments, the yield increase and nitrogen agronomic efficiency of nitrogen fertilizer application were obtained: nitrogen fertilizer yield increase = total nitrogen, phosphorus, and potassium yield - yield of phosphorus and potassium alone = target yield × (1-nitrogen supply level parameter); nitrogen agronomic efficiency = (total nitrogen, phosphorus, and potassium yield - yield of phosphorus and potassium alone) / nitrogen application rate. A quadratic equation was used to fit the relationship between nitrogen agronomic efficiency and nitrogen fertilizer yield increase to determine the values ​​of a, b, and c. Phosphorus application rate = target yield × (1-relative phosphorus yield) × aboveground phosphorus absorption per unit yield ÷ phosphorus fertilizer utilization rate + target yield × phosphorus absorption per unit grain yield × phosphorus balance coefficient; Among them, the utilization rate of phosphorus fertilizer is calculated according to the utilization rate of the season, which is 10% to 30%; the phosphorus balance coefficient determined according to the nutrient balance principle is 0.5 to 1.0; 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, which is 30% to 70%; the potassium balance coefficient determined according to the nutrient balance principle is 0.1 to 0.5; (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 rice straw in a single season are 55.3%, 62.7% and 83.1% respectively, and the effectiveness is 30%, 20% and 30% respectively; (6) determining the final application amounts of nitrogen, phosphorus, and potassium fertilizers for a rice crop according to 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 fertilizer for the next rice crop by returning straw to the field according to claim 1, characterized in that: The nitrogen, phosphorus and potassium in the special fertilizer for single-season rice are applied in batches, and are divided into special fertilizer for base fertilizer, special fertilizer for tillering and special fertilizer for heading; among them, the special fertilizer for base fertilizer accounts for 40% of the final nitrogen application amount, the special fertilizer for tillering accounts for 25% of the final nitrogen application amount, and the special fertilizer for heading accounts for 35% of the final nitrogen application amount; the special fertilizer for base fertilizer accounts for 100% of the final phosphorus application amount; the special fertilizer for base fertilizer, special fertilizer for tillering and special fertilizer for heading each account for 1 / 3 of the final potassium application amount.

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