Fertilizer preparation method of special fertilizer for double cropping rice rotation system crops under straw returning

Abstract

The invention discloses a method for preparing a special fertilizer for double cropping rice crop rotation system crops under straw returning, and belongs to the technical field of 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 the double cropping rice 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 invention belongs to the technical field of rice rotation, and particularly relates to a method for allocating special fertilizers for crops in a double-season rice rotation system with straw returned to the field. Background Art

[0002] In agricultural production, returning straw to fields has become a common practice. As a measure to improve soil fertility and increase crop yields, long-term straw return has a significant effect on improving soil structure and increasing soil organic matter content. Straw contains a rich source of carbon. After returning the carbon to the fields, soil microorganisms decompose it to form a large amount of organic carbon, which is stored in the soil, thereby increasing the soil organic matter content and improving soil fertility. In addition, returning straw to the fields increases the soil's aggregate structure and the number of aggregates, increasing soil porosity, and thus enhancing the soil's water infiltration and water retention capacity. Returning straw to the fields also avoids air pollution caused by straw burning, thus protecting the environment. Burning straw produces large amounts of smoke, which affects air quality and even the urban environment. Therefore, returning straw to the fields is of great significance for improving the environment and the efficient use of crop resources.

[0003] The nitrogen, phosphorus, and potassium contained in straw are valuable resources. Returning straw to the fields can increase soil nutrient content and reduce the use of chemical fertilizers, thereby promoting crop growth and improving crop yield and quality. However, the nutrients in straw cannot be directly absorbed and utilized by crops and must be decomposed by microorganisms. This is a long process that involves the nutrient release rate of straw after returning to the fields. Although returning straw to the fields can increase soil organic matter content, improve soil structure and water retention capacity to a certain extent, it faces many challenges in actual operation. For example, after straw is directly returned to the fields, the high soil carbon-nitrogen ratio causes microorganisms to compete with crops for nitrogen. Therefore, it is very necessary to determine a reasonable amount of fertilizer when returning straw to the fields.

[0004] The early-late rice system plays a vital role in ensuring food security. However, long-term, high-intensity cropping has led to a continuous decline in soil fertility, while excessive fertilization has also reduced fertilizer utilization efficiency. In the Yangtze River Basin, cultivating early-late rice fully utilizes land and light and heat resources, increasing the number of rice plantings, thereby increasing yield per unit area and total output. This practice allows for better planning of agricultural activities, optimizes resource allocation, and improves the efficiency of land and water use. Fertilizers, as a key pillar of sustainable modern agriculture, significantly contribute to crop yields, but they also face challenges such as excessive application leading to resource waste. The rice growing environment is also highly susceptible to fertilizer loss and environmental pollution. Furthermore, straw is rich in nitrogen, phosphorus, and potassium. Fully utilizing these nutrients can further reduce fertilizer application and increase efficiency. However, factors such as straw nutrient content, straw nutrient release rate, and crop rotation system directly influence fertilizer application rates. Nutrient inputs at different growth stages also vary after straw incorporation, posing new challenges for optimizing fertilizer formulations. Summary of the Invention

[0005] The present invention aims to provide a method for formulating fertilizers specifically for crops in a double-season rice rotation system using straw return. Specifically, by optimizing key parameters such as nutrient uptake and release rate from the previous crop straw, a method for calculating the nitrogen, phosphorus, and potassium nutrient requirements for specific fertilizers at different growth stages in a double-season rice rotation system is proposed. This method effectively improves crop yield and soil fertility in a double-season rice rotation system using straw return, reducing the use of chemical fertilizers and increasing their efficiency. This method can provide technical support for fertilizer manufacturers in formulating specific fertilizers for crops in a double-season rice rotation 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 dispensing fertilizer specifically for crops in a double-season rice rotation system under straw return, 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 early and late rice rotation systems:

[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 to be used is determined based on the target yield of early and late rice, nutrient requirements per unit yield, the 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: 15% to 35% for both early and late rice; based on the principle of nutrient balance, the phosphorus balance coefficient for both early and late rice is determined to be 0.6 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: 40% to 70% for both early and late rice; based on the principle of nutrient balance, the potassium balance coefficient for both early and late rice is determined to be 0.2 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 early rice straw are 67.5%, 79.0% and 98.0% respectively, and the nitrogen, phosphorus and potassium nutrient availability of early rice straw to the late rice season is 40%, 30% and 40% respectively;

[0040] The nitrogen, phosphorus and potassium nutrient release rates of late rice straw were 52.5%, 80.0% and 97.5% respectively, and the nitrogen, phosphorus and potassium nutrient availability of late rice straw to the early rice season was 30%, 20% and 30% respectively;

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

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

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

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

[0045] Preferably, the nitrogen, phosphorus and potassium in the early rice-late rice special fertilizer are applied in several times, and are divided into base fertilizer special fertilizer, tillering special fertilizer and booting special fertilizer; wherein, the base fertilizer special fertilizer accounts for 40% of the final application amount of nitrogen, the tillering special fertilizer accounts for 25% of the final application amount of nitrogen, and the booting special fertilizer accounts for 35% of the final application amount of nitrogen; the base fertilizer special fertilizer accounts for 100% of the final application amount of phosphorus; and the base fertilizer special fertilizer, the tillering special fertilizer and the booting special fertilizer each accounts for 1 / 3 of the final application amount of potassium.

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

[0047] 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; and the conventional fertilization of farmers is optimized by comprehensively considering the nutrient brought by straw of previous crop, the nutrient release rate and availability of straw, the higher carbon-nitrogen ratio under straw returning, and the apparent balance of phosphorus and potassium in the soil of the production area. Compared with the conventional fertilization of farmers, the optimized recommended fertilization formula of the present application not only contains the nutrient of straw of previous crop, but also gives special fertilizer formula for main growth stages. The special fertilizer formula for crops in the double-cropping rice rotation system under straw returning provided by the present application can not only improve the yield of crops, but also improve the nutrient use efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 It is a schematic diagram of the special fertilizer formula fertilization method for crops in the double-cropping rice rotation system under straw returning in embodiment 1 of the present application. DETAILED DESCRIPTION

[0049] The various illustrative embodiments of the present application will now be described in detail in connection with the following figures. This description is not to be considered limiting in scope, but rather as being exemplary of the various aspects, features and implementations of the present application. It is understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0050] 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.

[0051] In addition, for numerical ranges of the present application, it is to be understood that every intermediate value of the upper and lower limits of the range is specifically contemplated. Any intermediate value of any stated value or stated range, as well as any other stated value or intermediate value of the stated range, is also encompassed within the present application. The upper and lower limits of these smaller ranges can independently be included or excluded in the ranges.

[0052] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as those of ordinary skill in the art to which the application relates. 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.

[0053] With respect to the use of "comprising", "including", "containing", "having" and "ensing" and the like, these terms are used in the broadest sense of the term to the extent permitted by law, and are used inclusively and in the sense of "including but not limited to".

[0054] The schematic diagram of the method for matching fertilizers for crops in the double-cropping rice rotation system with straw incorporated in Example 1 of the present application is shown in Figure 1 .

[0055] Example 1

[0056] Step A1: Before the crops are planted, uniform distribution of soil samples is carried out 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;

[0057] The pre-sowing soil test values are: organic matter 22.5 g / kg, hydrolyzable nitrogen 95.3 mg / kg, available phosphorus 13.7 mg / kg and available potassium 107.8 mg / kg.

[0058] Step A2: On the basis of step A1, the soil nitrogen, phosphorus and potassium nutrient supply grade is determined; wherein the soil nitrogen, phosphorus and potassium nutrient supply grade is related to the test results of the organic matter, available phosphorus and available potassium in the soil, and the specific relationship is shown in Table 1, wherein the organic matter content corresponds to the soil nitrogen supply grade, but when the soil hydrolyzable nitrogen is ≥180 mg / kg, the test grade "low" of the organic matter is upgraded to the test grade "medium"; when the hydrolyzable nitrogen is ≤100 mg / kg, the test grade "high" of the organic matter is downgraded to the test grade "medium";

[0059] The soil organic matter before sowing is 22.5 g / kg, which is between 10-30 g / kg, and is of medium grade, and the soil nitrogen supply level does not need to be adjusted, and is also of medium grade; the available phosphorus is 13.7 mg / kg, which is between 10-25 mg / kg, and is of medium grade; the available potassium is 107.8 mg / kg, which is between 80-150 mg / kg, and is of medium grade;

[0060] The soil nutrient test values of the recommended fertilization plots are finally determined to be of medium grade for the soil nitrogen, phosphorus and potassium supply levels.

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

[0062]

[0063] Step A3: Determine the target yield, increase the yield of the farmer's customary fertilization measure by 10%, and take the farmer's customary yield of early rice as 6 t / ha and late rice as 8 t / ha as an example, wherein the target yield is:

[0064] Early rice: 6+6x10%=6.6 t / ha;

[0065] Late rice: 8+8x10%=8.8 t / ha.

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

[0067] Calculate the nitrogen relative yield, phosphorus relative yield and potassium relative yield based on the yield of applying only two of nitrogen, phosphorus and potassium fertilizers and full application of fertilizers;

[0068] Nitrogen relative yield=only phosphorus and potassium application yield÷nitrogen, phosphorus and potassium full application yield;

[0069] Phosphorus relative yield=only nitrogen and potassium application yield÷nitrogen, phosphorus and potassium full application yield;

[0070] Potassium relative yield=only nitrogen and phosphorus application yield÷nitrogen, phosphorus and potassium full application yield;

[0071] The early rice nitrogen, phosphorus and potassium relative yield data are 377, 293 and 304, respectively;

[0072] The late rice soil nitrogen, phosphorus and potassium relative yield data are 461, 332 and 338, respectively;

[0073] The 25th percentile, 50th percentile and 75th percentile of the nitrogen, phosphorus and potassium relative yield are determined as the parameters of the "low", "medium" and "high" levels of nitrogen, phosphorus and potassium supply;

[0074] The obtained early rice and late rice nitrogen, phosphorus and potassium soil nutrient supply level parameters are shown in Table 2.

[0075] Table 2 Corresponding parameters of nitrogen, phosphorus and potassium soil nutrient supply levels for early and late 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 early rice were 0.700, 0.888, and 0.883, respectively; and the corresponding soil nitrogen, phosphorus, and potassium level parameters for late rice were 0.747, 0.907, and 0.905, respectively.

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

[0079] First, collect data on early-late rice field trials or arrange field trials. The data must include grain yield, straw yield, and nitrogen, phosphorus, and potassium nutrient uptake;

[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 early rice were calculated to be 18.9, 3.7, and 22.5 kg / t, respectively; the aboveground nitrogen, phosphorus, and potassium nutrient requirements per unit yield of late rice were 19.9, 4.2, and 23.5 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 early rice are 12.5, 2.6 and 3.9 kg / t respectively; the nitrogen, phosphorus and potassium nutrient requirements per unit yield of late rice are 12.8, 2.9 and 4.0 kg / t respectively.

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

[0086] Nitrogen absorption of early rice straw = 18.9-12.5 = 6.4 kg / t;

[0087] Nitrogen absorption of early rice straw = 3.7-2.6 = 1.1 kg / t;

[0088] Nitrogen absorption of early rice straw = 22.5-3.9 = 18.6 kg / t;

[0089] Late rice straw nitrogen absorption = 19.9-12.7 = 7.1 kg / t;

[0090] Late rice straw nitrogen absorption = 4.2-2.9 = 1.3 kg / t;

[0091] Late rice straw nitrogen absorption = 23.5-4.0 = 19.5 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 early rice and late 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 recycling rate. The phosphorus and potassium recycling rates for early rice and late rice are adjusted to 30% and 60% respectively.

[0095] Determine the nutrient balance coefficients, where the nutrient balance coefficients for early rice grain phosphorus and straw potassium are determined to be 1.0 and 0.3, respectively; the nutrient balance coefficients for late rice grain phosphorus and straw potassium are determined to be 1.0 and 0.2, respectively;

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

[0097] Early rice:

[0098] Based on a large number of previous field experiments, the nitrogen agronomic efficiency calculation formula for early rice in the main double-season rice producing areas of Jiangxi Province was determined to be a=-0.3904,b=7.0522,c=0.1341;

[0099] Nitrogen application rate = (6.6 × (1-0.700) × 1000) ÷ [-0.3904 × (6.6 × (1-0.700)) 2 +7.0522×6.6×(1-0.700)+0.1341]=157.6kg / ha;

[0100] Phosphorus application rate = 6.6 × (1 - 0.888) × 3.7 ÷ 30% + 6.6 × 2.6 × 1.0 = 26.3 kg / ha;

[0101] Potassium application rate = 6.6 × (1-0.883) × 22.5 ÷ 60% + 6.6 × 3.9 × 1.0 + 6.6 × 18.6 × 0.3 = 91.5 kg / ha;

[0102] Late rice:

[0103] Based on a large number of previous field experiments, the nitrogen agronomic efficiency calculation formula for late rice in the main double-season rice producing areas of Jiangxi Province was determined to be a=-0.367,b=6.5182,c=0.2464;

[0104] Nitrogen application rate = (8.8 × (1-0.747) × 1000) ÷ [-0.367 × (8.8 × (1-0.747)) 2 +6.5182×8.8×(1-0.747)+0.2464]=172.1kg / ha;

[0105] Phosphorus application rate = 8.8 × (1-0.907) × 4.2 ÷ 30% + 8.8 × 2.9 × 1.0 = 37.0 kg / ha;

[0106] Potassium application rate = 8.8 × (1-0.905) × 23.5 ÷ 60% + 8.8 × 4.0 × 1.0 + 8.8 × 19.5 × 0.2 = 102.3 kg / ha.

[0107] Step A8: Determine the amount of nutrients introduced by the preceding crop straw, where the preceding crop for early rice is late rice and the farmer's yield is 6 t / ha, and the preceding crop for late rice is early rice and the farmer's yield is 8 t / ha;

[0108] The release rates of nitrogen, phosphorus and potassium nutrients from early rice straw were 67.5%, 79.0% and 98.0% respectively, and the availability of nitrogen, phosphorus and potassium nutrients from early rice straw to late rice season was 40%, 30% and 40% respectively;

[0109] The nitrogen, phosphorus and potassium nutrient release rates of late rice straw were 52.5%, 80.0% and 97.5% respectively, and the nitrogen, phosphorus and potassium nutrient availability of late rice straw to the early rice season was 30%, 20% and 30% respectively;

[0110] Amount of nutrients brought into the straw of the previous crop, late rice, during the early rice planting season:

[0111] Nitrogen intake from the previous crop late rice straw = 8 × 7.1 × 52.5% × 30% = 8.9 kg / ha;

[0112] Phosphorus introduced from the previous crop late rice straw = 8 × 1.3 × 80.0% × 20% = 1.7 kg / ha;

[0113] Potassium intake from the previous crop late rice straw = 8 × 19.5 × 97.5% × 30% = 45.6 kg / ha;

[0114] Amount of nutrients brought into the straw of the early rice crop before the late rice planting season:

[0115] Nitrogen introduced from the previous crop early rice straw = 6 × 6.4 × 67.5% × 40% = 10.4 kg / ha;

[0116] Phosphorus introduced from the previous crop early rice straw = 6 × 1.1 × 79.0% × 30% = 1.6 kg / ha;

[0117] The amount of potassium brought in by the straw of the previous crop, early rice = 6 × 18.6 × 98.0% × 40% = 43.7 kg / ha.

[0118] Step A9: Determine the final fertilizer NPK dosage for the early rice-late rice rotation system:

[0119] Early rice:

[0120] Final nitrogen application rate = 157.6-8.9 = 148.7 kg / ha;

[0121] Final phosphorus application rate = 26.3-1.7 = 24.6 kg / ha;

[0122] Final potassium application rate = 91.5-45.6 = 45.9 kg / ha;

[0123] Late rice:

[0124] Final nitrogen application rate = 172.1-10.4 = 148.7 kg / ha;

[0125] Final phosphorus application rate = 37.0-1.6 = 35.4 kg / ha;

[0126] Final potassium application rate = 102.3-43.7 = 58.6 kg / ha.

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

[0128] The main fertilization stages during the rice growth period are transplanting, tillering, and heading stages. The corresponding special fertilizers for early rice and late rice 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.

[0129] According to the final nitrogen, phosphorus and potassium application rates and application methods of early rice, the application rates of N, P and K in the base fertilizer were determined to be 59.5, 24.6 and 15.3 kg / ha respectively, which were converted to N, P2O5 and K2O, respectively, 59.5, 24.6×2.292 and 15.3×1.205, i.e. 59.5, 56.4 and 18.4 kg / ha;

[0130] According to the final nitrogen, phosphorus and potassium application rates and application methods of early rice, the application rates of N, P and K in the tillering fertilizer were determined to be 37.2, 0 and 15.3 kg / ha respectively, which were converted into 37.2, 0 and 19.8×1.205 of N, P2O5 and K2O, i.e. 37.2, 0 and 18.4 kg / ha respectively;

[0131] According to the final nitrogen, phosphorus and potassium application rates and application methods of early rice, the application rates of N, P and K in the special fertilizer for booting were determined to be 53.0, 0 and 15.3 kg / ha respectively, which were converted into 53.0, 0 and 15.3×1.205 of N, P2O5 and K2O, i.e. 53.0, 0 and 18.4 kg / ha respectively;

[0132] According to the final nitrogen, phosphorus and potassium application rates and application methods of late rice, the application rates of N, P and K in the base fertilizer were determined to be 64.7, 35.4 and 19.5 kg / ha respectively, which were converted to N, P2O5 and K2O, respectively, 64.7, 35.4×2.292 and 19.5×1.205, i.e. 64.7, 81.1 and 23.5 kg / ha;

[0133] According to the final nitrogen, phosphorus and potassium application rates and application methods of late rice, the application rates of N, P and K in the tillering fertilizer were determined to be 40.4, 0 and 19.5 kg / ha respectively, which were converted to N, P2O5 and K2O as 40.4, 0 and 19.5×1.205, i.e. 40.4, 0 and 23.5 kg / ha respectively;

[0134] According to the final nitrogen, phosphorus and potassium application rates and application methods of late rice, the application rates of N, P and K in the special fertilizer for booting were determined to be 56.6, 0 and 19.5 kg / ha respectively, which were converted into 56.6, 0 and 19.5×1.205 for N, P2O5 and K2O, i.e. 56.6, 0 and 23.5 kg / ha respectively;

[0135] Finally, the total nutrient content and corresponding N:P2O5:K2O grades of special fertilizers for early rice and late rice were determined according to GB 15063-2001 standard.

[0136] In the main double-season rice-producing areas of Jiangxi Province, two fertilization scenarios—conventional fertilization and optimized fertilization—were established, with conventional fertilization as the 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.

[0137] Table 3

[0138]

[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 early and late rice yield and nutrient recovery. Field test results showed that compared with conventional fertilization, optimized fertilization reduced fertilizer application rates: nitrogen application rates for early and late rice decreased by 14.9% and 16.9%, phosphorus application rates decreased by 25.3% and 4.7%, and potassium application rates decreased by 51.8% and 40.8%, respectively. However, yields increased by 7.3% and 6.4%, respectively. Nitrogen recovery rates increased by 13.3 and 13.9 percentage points, phosphorus recovery rates increased by 16.6 and 9.2 percentage points, and potassium recovery rates increased by 16.2 and 15.1 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 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.

[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 double-season rice rotation system under straw return, characterized in that: The following steps are involved: (1) Determine the soil nutrient supply level based on the soil nutrient test value before sowing: The soil test indicators include organic matter, hydrolyzable nitrogen, available phosphorus and available potassium; the soil nitrogen nutrient supply level is determined based on the content of soil organic matter and hydrolyzable nitrogen, the soil phosphorus nutrient supply level is determined based on the content of soil available phosphorus, and the soil potassium nutrient supply level is determined based on the content of soil available potassium; Among them, when the organic matter content is <10g / kg, the organic matter test level is "low", when the organic matter content is 10-30g / kg, the organic matter test level is "medium", and when the organic matter content is >30g / kg, the organic matter test level is "high"; the organic matter test levels of "low", "medium" and "high" correspond to the soil nitrogen supply levels of "low", "medium" and "high" respectively; however, when the soil hydrolyzable nitrogen is ≥180mg / kg, the organic matter test level of "low" is upgraded to the test level of "medium"; when the hydrolyzable nitrogen is ≤100mg / kg, the organic matter test level of "high" is downgraded to the test level of "medium"; When the available phosphorus content is less than 10 mg / kg, the available phosphorus test grade is "low", when the available phosphorus content is between 10 and 25 mg / kg, the available phosphorus test grade is "medium", and when the available phosphorus content is greater than 25 mg / kg, the available phosphorus test grade is "high". The "low", "medium" and "high" available phosphorus test grades correspond to the "low", "medium" and "high" soil phosphorus supply grades, respectively. When the available potassium content is less than 80 mg / kg, the available potassium test level is "low", when the available potassium content is between 80 and 150 mg / kg, the available potassium test level is "medium", and when the available potassium content is greater than 150 mg / kg, the available potassium test level is "high". The "low", "medium" and "high" levels of the available potassium test correspond to the "low", "medium" and "high" levels of soil potassium supply, respectively. (2) Determine the parameters for "low", "medium" and "high" levels of soil nitrogen, phosphorus and potassium supply: The relative yields of nitrogen, phosphorus and potassium were calculated based on the yields of applying only two of the nitrogen, phosphorus and potassium fertilizers and the yields of applying all fertilizers; Relative nitrogen yield = yield of phosphorus and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined; Relative phosphorus yield = yield of nitrogen and potassium alone ÷ yield of nitrogen, phosphorus and potassium combined; Relative potassium yield = yield of nitrogen and phosphorus alone ÷ yield of nitrogen, phosphorus and potassium combined; N groups of experiments were conducted to obtain N nitrogen relative yields, N phosphorus relative yields, and N potassium relative yields; among them, the 25th, 50th, and 75th percentiles of the N nitrogen relative yields were determined as parameters for the "low", "medium", and "high" levels of nitrogen supply; the 25th, 50th, and 75th percentiles of the N phosphorus relative yields were determined as parameters for the "low", "medium", and "high" levels of phosphorus supply; and the 25th, 50th, and 75th percentiles of the N potassium relative yields were determined as parameters for the "low", "medium", and "high" levels of potassium supply. (3) Determine the nutrient requirements per unit yield of the early and late rice rotation systems: 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 to be used is determined based on the target yield of early and late rice, nutrient requirements per unit yield, the 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: 15% to 35% for both early and late rice; based on the principle of nutrient balance, the phosphorus balance coefficient for both early and late rice is determined to be 0.6 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: 40% to 70% for both early and late rice; based on the principle of nutrient balance, the potassium balance coefficient for both early and late rice is determined to be 0.2 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 early rice straw are 67.5%, 79.0% and 98.0% respectively, and the nitrogen, phosphorus and potassium nutrient availability of early rice straw to the late rice season is 40%, 30% and 40% respectively; The nitrogen, phosphorus and potassium nutrient release rates of late rice straw were 52.5%, 80.0% and 97.5% respectively, and the nitrogen, phosphorus and potassium nutrient availability of late rice straw to the early rice season was 30%, 20% and 30% respectively; (6) determining the final nitrogen, phosphorus, and potassium fertilizer application rates for early rice and late rice 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 dispensing special fertilizers for crops in a double-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 early rice and late 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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