A soybean-rice rotation area straw returning and precision fertilization combined cultivation method

Abstract

The present application belongs to the technical field of rice-soybean rotation cultivation, and discloses a soybean-rice rotation area straw returning to field and precision fertilization synergistic cultivation method; taking cross-season continuous nutrient settlement account book as the core, after the crushed straw of the previous crop soybean is returned to field, a decomposing bacteria agent is applied, the straw nutrient release dynamic curve is regularly monitored, the equivalent of the released nutrients of the straw is deducted before rice transplanting, base fertilizer is applied, the amount of topdressing is dynamically reviewed and adjusted at the growth period node, after the rice is harvested, the amount of released nutrients of the returned straw is calculated by isotope tracing and is added to the account book, the next season soybean fertilization deducts the settled nutrients, and the related parameters are automatically corrected after the rotation period ends. The method can precisely match the straw nutrient release and the crop fertilizer demand rhythm, reduce the occurrence rate of seedling growth inhibition and late-season late maturity, improve the utilization rate of straw nutrients and reduce the amount of chemical fertilizer application, and the parameter self-correction mechanism can guarantee the long-term stable yield adaptability and adapt to the soil conditions of different rice-soybean rotation planting areas.

Description

Technical Field

[0001] This invention belongs to the field of rice-soybean rotation cultivation technology, and in particular to a method for the coordinated cultivation of straw return and precision fertilization in soybean-rice rotation areas. Background Technology

[0002] Rice-soybean rotation is a core water-dry rotation model in the middle and lower reaches of the Yangtze River and the Huanghuai region of my country. It has the functions of stabilizing grain and oil production and improving soil fertility. Under the current background of green transformation of agriculture, returning all straw to the field and reducing the application of chemical fertilizers are the core management objectives of production in this region. The core demand of the industry is to achieve the synergy of efficient utilization of straw nutrients and stable crop yield.

[0003] One of the current mainstream technologies is a regionally unified straw return to the field technology coupled with a fixed proportion of fertilizer reduction. Its working principle is to uniformly set a fertilizer reduction ratio of 15% to 25% based on the region's average straw return volume over many years. No additional testing is required during production; the fixed plan is followed directly. This technology is easy to operate, suitable for large-scale production, and has a high adoption rate at the grassroots level. However, this technology does not consider the impact of differences in soil moisture and fertility levels on the straw decomposition rate in different fields, and cannot match the actual release progress of straw nutrients. This can easily lead to problems such as nitrogen competition inhibiting crop seedling growth in the early stages of straw decomposition, or nutrient excess leading to leaching and delayed crop maturity in the later stages. Furthermore, it does not include the cross-seasonal nutrient carryover accounting in crop rotation, resulting in a waste of straw nutrient resources.

[0004] Another mainstream technology is single-season soil testing and fertilizer recommendation. Its working principle involves collecting soil samples before crop sowing to determine the content of readily available nutrients, and then combining this with the target yield to determine the total amount of fertilizer to be applied in the current season, significantly improving accuracy compared to a fixed reduction model. However, this technology only measures the static nutrient content of the soil before crop sowing, failing to cover the dynamic nutrient release process throughout the entire crop growth period after straw return. Furthermore, it does not distinguish between the effectiveness of nutrients released from straw and those from chemical fertilizers. Directly deducting fertilizer application based on equal nutrient ratios can easily lead to fertilization deviations. Moreover, it lacks a rolling nutrient accounting mechanism across crop rotation cycles, making it impossible to achieve continuous and coordinated utilization of nutrients from two crop seasons.

[0005] The aforementioned existing technologies are all ill-suited to the characteristics of large differences in straw decomposition rhythm and significant cross-seasonal nutrient carryover effects under the rice-soybean water-dry rotation system. They cannot meet the synergistic needs of efficient straw nutrient utilization, precise reduction of fertilizer application, and stable crop yield. Corresponding technical solutions are urgently needed to break through the existing technical bottlenecks. Summary of the Invention

[0006] To address the shortcomings of existing rice-soybean rotation systems, such as nutrient supply and demand mismatch, large deviations in cross-seasonal nutrient calculation, and low precision in reducing fertilizer application, this invention provides a method for the coordinated cultivation of straw return and precision fertilization in soybean-rice rotation areas.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for co-cultivation of straw return and precision fertilization in soybean-rice rotation areas suitable for paddy soil or alluvial soil in the middle and lower reaches of the Yangtze River and the Huang-Huai region, is based on a cross-seasonal continuous nutrient carryover ledger. It achieves dynamic nutrient hedging based on a dynamic rolling algorithm of straw-released nutrient equivalents and fertilizer deductions. The method includes the following steps: S1: After the previous soybean harvest, the soybean straw is crushed to a length of less than 5cm and evenly spread on the field surface. After applying the decomposing microbial agent, it is rotary tilled and mixed. The rotary tillage depth is 15cm~20cm. The soil moisture is adjusted to 60%~70% of the field water holding capacity. After returning to the field, soil samples and straw bag samples are collected regularly in an independent sampling area according to the time nodes of dense decomposition in the early stage and sparse decomposition in the later stage. The straw weight loss rate and the content of available nutrients in the soil are measured. Based on this, the dynamic curve of straw nutrient release in the field is obtained by fitting and the release of nitrogen, phosphorus and potassium from straw at each time period is calculated. S2: Before rice transplanting, the recommended amount of basal fertilizer under local soil testing and formula fertilization or conventional cultivation conditions is used as the recommended amount of basal fertilizer to determine the total nitrogen, phosphorus, and potassium requirements of rice throughout its growth period. Based on the straw nutrient release dynamic curve obtained in S1, the straw nitrogen, phosphorus, and potassium release from transplanting to the tillering stage is extrapolated and predicted. These values ​​are then multiplied by independently set equivalent coefficients to convert them into fertilizer nutrient deductions, which are deducted from the rice basal fertilizer. The actual nitrogen application rate of the basal fertilizer is calculated according to formula (I): In the formula This refers to the actual amount of nitrogen applied as base fertilizer. This is the recommended amount for regular base fertilizer. This is the base fertilizer coefficient, and its value ranges from 0.5 to 0.8. To predict nitrogen release from straw before the tillering stage, The nitrogen equivalent coefficient is 0.3 to 0.7. When the calculated value is... Below At 30%, according to 30% of the actual nitrogen application amount is used as base fertilizer, and the straw nutrient equivalent that could not be deducted from the base fertilizer is included in the aforementioned cross-seasonal nutrient carry-over ledger. The actual amount of phosphorus fertilizer applied is the product of the recommended amount of phosphorus fertilizer applied to conventional base fertilizer and the predicted amount of phosphorus released from straw and the phosphorus equivalent coefficient. The actual amount of potassium fertilizer applied is the product of the recommended amount of potassium fertilizer applied to conventional base fertilizer and the predicted amount of potassium released from straw and the potassium equivalent coefficient. The actual amount of phosphorus and potassium fertilizer applied after deduction is not less than 30% of the recommended amount of conventional base fertilizer. The phosphorus and potassium nutrient equivalent that cannot be deducted from the base fertilizer is included in the cross-seasonal nutrient carry-over ledger. S3: After rice transplanting, the release of nutrients from straw is dynamically verified before the tillering stage, the jointing and booting stage, and the grain-filling stage. The dynamic verification is carried out by taking straw bag samples from independent sampling areas to determine the straw weight loss rate and nutrient content, and is completed at least 5 days before the corresponding topdressing node. Based on the recommended nitrogen amount for topdressing at each growth stage according to local soil testing and fertilizer formula, the actual nitrogen amount applied for topdressing is the recommended nitrogen amount for the current period minus the product of the measured nitrogen release from straw and the nitrogen equivalent coefficient, and minus the corresponding carry-over deduction amount recorded in S2. If the calculated value after deduction is less than 10% of the recommended nitrogen amount for the current period, then 10% of the recommended nitrogen amount for the current period shall be applied. Phosphorus and potassium fertilizers shall be deducted independently according to the same rules, and their respective minimum guaranteed application amounts shall be set. At the same time, the actual amount of fertilizer applied each time and the measured amount of straw release shall be recorded to form a nutrient carry-over ledger that is adjusted periodically. S4: After rice harvest, rice straw is crushed to a length of less than 5cm and returned directly to the field. Urea is applied to adjust the carbon-nitrogen ratio to 25:1~30:1. After rotary tillage and mixing, soil moisture is adjusted. After returning to the field, the rice straw decomposition rate and soil available nutrient content are measured in an independent sampling area according to the time nodes of dense decomposition in the early stage and sparse decomposition in the later stage. Among them, a control sampling area with the same carbon-nitrogen ratio as the main urea application area but with isotope-labeled urea is set up. The contribution of urea nitrogen is deducted by isotope tracing to determine the nutrient amount released by the rice straw itself. The urea nitrogen used to adjust the carbon-nitrogen ratio is recorded separately and is not included in the nutrient carry-over balance. The nutrients actually released by the rice straw are included in the same cross-season nutrient carry-over ledger as the available nutrient balance for the next season's soybean fertilization. S5: Before soybean sowing, prepare soybean base fertilizer according to the nutrient balance carried over from rice straw. The base fertilizer only contains phosphorus and potassium fertilizer, molybdenum fertilizer, and boron fertilizer, and does not contain nitrogen components. After sowing, apply urea only once during the seedling stage. The amount of nitrogen applied during the seedling stage is the nitrogen requirement of soybean seedlings minus the effective nitrogen balance carried over from rice straw in the nutrient carryover ledger. If the calculated value is less than 10% of the nitrogen requirement of soybean seedlings, apply 10%; otherwise, apply the calculated value. During the grain filling stage, foliar spray phosphorus and potassium fertilizer is applied according to the growth. S6: After the crop rotation cycle ends, the model prediction value of the straw nutrient release dynamic curve is compared with the measured value of the same field. Based on the error between the two, the equivalent coefficient and release rate parameters of the next cycle are corrected to achieve self-correction year by year.

[0008] Preferably, the sampling time nodes in S1 and S4 include days 1, 3, 5, 7, 14, 21 and 28 after returning the straw to the field, with no less than 5 sampling points at each time node, and 3 parallel replicates for each group of samples; the dynamic curve of straw nutrient release is fitted using a Logistic model or an exponential decay model.

[0009] Preferably, the decomposing microbial agent mentioned in S1 is a compound microbial agent of Bacillus subtilis and Aspergillus niger, with an effective viable count of not less than 200 million / g, and an application rate of 15kg~30kg per hectare.

[0010] Preferably, the equivalent coefficients of nitrogen, phosphorus, and potassium are set independently, wherein the equivalent coefficient of nitrogen is 0.3~0.5, the equivalent coefficient of phosphorus is 0.4~0.6, and the equivalent coefficient of potassium is 0.6~0.8; the equivalent coefficients for different growth stages and different straw types are set independently.

[0011] Preferably, in S1 and S4, the available nitrogen in the soil is determined by alkaline diffusion method, the available phosphorus in the soil is determined by Olsen method, and the available potassium in the soil is determined by ammonium acetate extraction flame photometry.

[0012] Preferably, when calculating the amount of fertilizer applied at each growth stage, the independent deductions for nitrogen, phosphorus, and potassium are calculated separately, and then summarized to form a complete fertilization plan for the current period, so that the deduction processes for different nutrients do not interfere with each other.

[0013] Preferably, in S4, after rice straw is returned to the field, the soil moisture is adjusted to 55%~65% of the field water holding capacity, and the rotary tillage depth is 15cm~20cm.

[0014] Preferably, the phosphorus and potassium fertilizer sprayed during the granulation stage of S5 is potassium dihydrogen phosphate solution, and the number of sprays is 1 to 2, with an interval of 7 to 10 days between the two sprays.

[0015] Preferably, when the error between the model prediction and the measured value in S6 exceeds 10%, the equivalent coefficient and release rate parameter of the nutrient type are adjusted accordingly. The adjustment range is positively correlated with the error magnitude. Specifically, when the relative error is 10%~20%, the equivalent coefficient is adjusted by 0.02~0.05, and when the relative error exceeds 20%, the equivalent coefficient is adjusted by 0.05~0.10.

[0016] Preferably, the independent sampling area is set within or adjacent to the main planting area, with an area of ​​not less than 3% of the field area. During the decomposition monitoring period, the independent sampling area performs the same straw return to field amount, rotary tillage depth, soil moisture management and water management operations as the main planting area. During the S1 decomposition monitoring period, no fertilization is performed in the independent sampling area. During the S4 decomposition monitoring period, the same amount and type of urea as the main planting area are applied to the independent sampling area to adjust the carbon-nitrogen ratio. A control sampling area with isotope-labeled urea is set up within the independent sampling area. After the decomposition monitoring period ends, the independent sampling area is incorporated into the main planting area, and subsequent crop fertilization is carried out according to the same fertilization plan as the main planting area. The control sampling area is only used for isotope tracer measurement during the decomposition monitoring period and is not included in yield statistics.

[0017] The present invention has the following beneficial effects: This invention uses in-situ straw decomposition monitoring in the field to fit a specific dynamic curve of nutrient release. Combined with nutrient equivalent coefficients set independently for different nutrients and different growth stages, it calculates the amount of fertilizer to be reduced. The application rate is dynamically reviewed and adjusted before each topdressing node of the crop, so as to achieve precise matching of nutrient supply and demand during the crop growth period. This effectively solves the problems of seedling growth suppression, nutrient loss or delayed maturity caused by the mismatch between straw nutrient release and crop nutrient demand rhythm in existing fixed-ratio fertilizer reduction technology, which does not take into account field heterogeneity.

[0018] This invention establishes a continuous nutrient carryover ledger across rice-soybean rotation cycles. It also employs isotope tracing technology to distinguish between nutrients released from rice straw itself and exogenous urea nutrients applied to adjust the carbon-nitrogen ratio. This enables the coordinated utilization of straw nutrients from both seasons and improves the accuracy of calculations. It effectively solves the problem of nutrient resource waste caused by existing single-season soil testing and formula fertilization technologies not covering cross-season nutrient carryover and large deviations in straw nutrient calculations.

[0019] This invention compares model predictions with actual field values ​​after the crop rotation cycle ends, and adjusts the nutrient equivalent coefficient and release rate parameters year by year, forming an iteratively optimized self-correction mechanism that can adapt to changes in soil fertility and decomposition conditions in different fields over a long period of time. This effectively solves the problem of fixed parameters and gradually declining adaptability of existing technologies over long periods of time.

[0020] This invention is applicable to all soybean-rice rotation production scenarios in paddy soil and alluvial soil types in the middle and lower reaches of the Yangtze River and the Huanghuai region. It does not require additional high-end testing equipment, and the operation process is in line with the existing grassroots agricultural technology extension habits. It is suitable for the production needs of small farmers' scattered planting, and can also be connected to the digital farmland management system of large-scale planting entities, and has high promotion and application value. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for synergistic cultivation of soybean-rice rotation area with straw return and precision fertilization proposed in this invention; Figure 2 This is a bar chart comparing the utilization efficiency of core nutrients in different groups proposed in this invention. Figure 3 This is a line graph showing the change in the yield achievement rate of the three consecutive seasons of crop rotation proposed in this invention. Figure 4 This is a bar chart comparing the adaptability and growth abnormality indicators of different groups proposed in this invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Indicator definition: Straw nutrient calculation error rate (%) = |Actual nutrient release from straw - Model predicted nutrient release| ÷ Actual nutrient release from straw × 100% Cross-season nutrient carryover utilization rate (%) = Actual carryover nutrients utilized by the subsequent season's crop ÷ Actual nutrients released from the previous season's straw × 100% Parameter adaptation deviation rate (%) = |Actual output for the current quarter - Target output| ÷ Target output × 100% Incidence of seedling growth inhibition (%) = Number of plants with inhibited seedling growth ÷ Total number of plants surveyed × 100% Late-maturing rate (%) = Number of plants that retain dark green leaves and have insufficient grain filling at maturity ÷ Total number of plants surveyed × 100% Production target achievement rate (%) = Actual output ÷ Target output × 100%,

[0024] Example 1: The test site for this example is a typical paddy soil planting area in Nanchang City, Jiangxi Province, in the middle and lower reaches of the Yangtze River. The crop rotation mode is early rice-summer soybean rotation.

[0025] S1: After the previous soybean harvest, crush the soybean stalks to an average length of 4cm and spread them evenly on the field surface. Apply a compound decomposing agent of Bacillus subtilis and Aspergillus niger with an effective live bacteria count of 220 million / g and an application rate of 15kg per hectare. After application, rotary tillage to mix the agent evenly to a depth of 15cm to adjust the soil moisture to 60% of the field capacity. An independent sampling area was set up, with an area of ​​4% of the field area, adjacent to the main planting area. During the decomposition monitoring period, the independent sampling area implemented the same straw return to the field, rotary tillage depth, moisture management and water management operations as the main planting area. No fertilization was carried out in the independent sampling area during the S1 decomposition monitoring period. Sampling was conducted regularly on days 1, 3, 5, 7, 14, 21, and 28 after soybean straw was returned to the field. Five sampling points were set up at each time point, and three parallel replicates were set up for each sample group. Soil samples and straw bag samples were collected. The available nitrogen in the soil was determined by alkaline hydrolysis diffusion method, the available phosphorus in the soil was determined by Olsen method, and the available potassium in the soil was determined by ammonium acetate extraction flame photometry method. At the same time, the straw weight loss rate was measured. The dynamic curve of nutrient release from soybean straw in this field was obtained by fitting the logistic model, and the release of nitrogen, phosphorus, and potassium from straw at each time point was calculated. S2: Before rice transplanting, the local soil testing and fertilizer recommendation for conventional basal fertilizer nitrogen application is 120 kg / ha. The total nitrogen requirement for rice during the entire growth period is 240 kg / ha, the total phosphorus requirement is 90 kg / ha, and the total potassium requirement is 150 kg / ha. Based on the straw nutrient release dynamic curve obtained in S1, the extrapolation predicts that the straw nitrogen release from transplanting to the tillering stage is 30 kg / ha, the phosphorus release is 8 kg / ha, and the potassium release is 35 kg / ha. The nitrogen equivalent coefficient is set independently as 0.3, the phosphorus equivalent coefficient is 0.4, and the potassium equivalent coefficient is 0.6. The basal fertilizer coefficient r is set to 0.5. According to formula (I), the actual nitrogen application of basal fertilizer is 51 kg / ha, which is 30% higher than the recommended nitrogen amount of conventional basal fertilizer, i.e., 36 kg / ha. It is applied at 51 kg / ha. The actual phosphorus application rate for phosphate fertilizer is 60 kg / ha minus 8 × 0.4 = 3.2 kg / ha, resulting in an actual phosphorus application rate of 56.8 kg / ha. This is 30% higher than the recommended phosphorus application rate for conventional base fertilizer, i.e., 18 kg / ha. Therefore, it should be applied at 56.8 kg / ha. Similarly, the actual potassium application rate for potash fertilizer is 90 kg / ha minus 35 × 0.6 = 21 kg / ha, resulting in an actual potassium application rate of 69 kg / ha. This is 30% higher than the recommended potassium application rate for conventional base fertilizer, i.e., 27 kg / ha. Therefore, it should be applied at 69 kg / ha. The deduction processes for nitrogen, phosphorus, and potassium nutrients are independent and do not interfere with each other. S3: After rice transplanting, dynamic verification of straw nutrient release was completed 5 days before the tillering stage, jointing and booting stage, and grain-filling stage. The verification was achieved by taking straw bag samples from independent sampling areas and measuring the straw weight loss rate and nutrient content. The nitrogen amount of topdressing recommended by local soil testing and fertilizer application for each growth stage was used as the benchmark. The actual nitrogen amount of topdressing was the recommended nitrogen amount of topdressing for the current period minus the product of the measured straw nitrogen release and the nitrogen equivalent coefficient. The calculated value after deduction was not less than 10% of the recommended nitrogen amount of topdressing for the current period. Phosphorus and potassium fertilizers are deducted independently according to the same rules, and corresponding minimum guaranteed application amounts are set for each. The actual amount of fertilizer applied each time and the measured amount of straw release are recorded in the ledger to form a nutrient carryover ledger that is revised periodically. In this embodiment, the calculated value after deduction for topdressing at each growth stage is higher than the lower limit of 10%, so the calculated value is applied. S4: After rice harvest, rice straw is shredded to an average length of 4cm and returned directly to the field. Urea is applied to adjust the carbon-to-nitrogen ratio to 25:1, and the straw is rotary tilled to a depth of 15cm to mix it thoroughly. Moisture is then adjusted to 55% of field capacity. During the decomposition monitoring period, the same amount and type of urea as in the main planting area is applied to the independent sampling area to adjust the carbon-to-nitrogen ratio. An additional 20m² area is set up within the independent sampling area. 2 The control sample area was treated with 15N-labeled urea with an abundance of 5 atom%, and the amount of 15N-labeled urea applied was the same as that of ordinary urea in the main area. Sampling was conducted on days 1, 3, 5, 7, 14, 21, and 28 after rice straw return to the field, with five sampling points at each time point and three parallel replicates for each sample group. The decomposition rate of rice straw and available nutrients in the soil were measured. The contribution of urea nitrogen was deducted by 15N isotope tracing to determine the amount of nutrients released by the rice straw itself. Urea nitrogen used to adjust the carbon-nitrogen ratio was recorded separately and not included in the nutrient carry-over balance. The nutrients actually released by the rice straw were included in the same cross-season nutrient carry-over ledger as the available nutrient balance for the next soybean fertilization season. After the decomposition monitoring period, the independent sampling area was merged into the main planting area, and subsequent soybean fertilization was carried out according to the same fertilization plan as the main planting area. The isotope control sample area was only used for isotope tracing measurements during the decomposition monitoring period and was not included in yield statistics. S5: Before sowing soybeans, prepare soybean base fertilizer according to the nutrient balance carried over from rice straw. The base fertilizer only contains phosphorus and potassium fertilizer, molybdenum fertilizer and boron fertilizer, and does not contain nitrogen components. The nitrogen requirement of soybean seedlings is 45 kg / ha. The effective nitrogen balance carried over from rice straw in the nutrient carryover ledger is 38 kg / ha. The nitrogen application rate during the seedling stage is 7 kg / ha, which is 10% higher than the nitrogen requirement of soybean seedlings, i.e., 4.5 kg / ha. Apply 7 kg / ha. Spray potassium dihydrogen phosphate solution once during the grain filling stage. S6: After the crop rotation cycle ends, compare the model-predicted value of the straw nutrient release dynamic curve with the measured value of the same field. The measured value of the same field refers to the total cumulative nutrient release of straw calculated from the last straw bag sample taken from the independent sampling area after the end of the S1 monitoring period, after drying, weighing, and nutrient determination. The relative error between the two is 8%, which does not exceed 10%, and there is no need to adjust the equivalent coefficient and release rate parameters for the next cycle.

[0026] Example 2: The test site for this example is a typical alluvial soil planting area in Zhoukou City, Henan Province, in the Yellow River and Huai River basin. The crop rotation pattern is winter wheat followed by summer soybean-late rice rotation.

[0027] S1: After the previous soybean harvest, crush the soybean stalks to an average length of 3cm and spread them evenly on the field surface. Apply a compound decomposing agent of Bacillus subtilis and Aspergillus niger with an effective live bacteria count of 250 million / g and an application rate of 30kg per hectare. After application, rotary tillage to mix the agent evenly to a depth of 20cm to adjust the soil moisture to 70% of the field capacity. An independent sampling area was set up, with an area of ​​3.5% of the field area, located inside the main planting area. During the decomposition monitoring period, the independent sampling area implemented the same straw return to the field, rotary tillage depth, soil moisture management and water management operations as the main planting area. No fertilization was carried out in the independent sampling area during the S1 decomposition monitoring period. Sampling was conducted regularly on days 1, 3, 5, 7, 14, 21, and 28 after the straw was returned to the field. Five sampling points were set up at each time point, and three parallel replicates were set up for each group of samples. Soil samples and straw bag samples were collected.

[0028] S2: Before rice transplanting, the base fertilizer nitrogen application rate under local conventional cultivation conditions is 135 kg / ha. The total nitrogen requirement for rice during the entire growth period is 270 kg / ha, the total phosphorus requirement is 105 kg / ha, and the total potassium requirement is 165 kg / ha. Based on the straw nutrient release dynamic curve obtained in S1, the straw nitrogen release rate from transplanting to the tillering stage is extrapolated to predict 36 kg / ha, phosphorus release rate is 10 kg / ha, and potassium release rate is 42 kg / ha. The nitrogen equivalent coefficient is set independently to 0.5, the phosphorus equivalent coefficient is 0.6, and the potassium equivalent coefficient is 0.8. The base fertilizer coefficient r is set to 0.8. According to formula (Ⅰ), the actual nitrogen application rate is 90 kg / ha, which is 30% higher than the recommended nitrogen application rate for conventional base fertilizers, i.e., 40.5 kg / ha. Therefore, it is applied at 90 kg / ha. The actual phosphorus application rate is 61.5 kg / ha, which is also 30% higher than the recommended phosphorus application rate for conventional base fertilizers. Therefore, it is applied at 61.5 kg / ha. The actual potassium application rate is 65.4 kg / ha, and it is applied at 65.4 kg / ha. The nitrogen, phosphorus, and potassium nutrient deduction processes are independent and do not interfere with each other.

[0029] S3: After rice transplanting, dynamic verification of straw nutrient release is conducted 6 days before the tillering, jointing and booting, and grain-filling stages. Verification is achieved by retrieving straw bag samples from independent sampling areas and measuring straw weight loss rate and nutrient content. Based on the recommended nitrogen amount for topdressing at each growth stage according to local soil testing and fertilizer recommendations, the actual nitrogen amount applied for topdressing is the product of the recommended nitrogen amount for the current period and the measured straw nitrogen release and nitrogen equivalent coefficient. The calculated value after deduction is not less than 10% of the recommended nitrogen amount for the current period. Phosphorus and potassium fertilizers are deducted independently according to the same rules, and corresponding minimum guaranteed application amounts are set for each. Each actual fertilizer application and measured straw release amount is recorded in a ledger, forming a nutrient carryover ledger that is updated periodically.

[0030] S4: After rice harvest, rice straw is shredded to an average length of 3cm and returned directly to the field. Urea is applied to adjust the carbon-nitrogen ratio to 30:1, and the straw is rotary tilled to a depth of 20cm to mix it thoroughly. Moisture is then adjusted to 65% of field capacity. During the decomposition monitoring period, the same amount and type of urea as in the main planting area is applied to the independent sampling area to adjust the carbon-nitrogen ratio. An additional 30m² area is set up within the independent sampling area. 2 The control sample area was treated with 15N-labeled urea with an abundance of 8 atom%, and the amount of 15N-labeled urea applied was the same as that of ordinary urea in the main area. Sampling was conducted at 1, 3, 5, 7, 14, 21, and 28 days after rice straw was returned to the field. Five sampling points were set at each time point, and three parallel replicates were set for each group of samples. The decomposition rate of rice straw and available nutrients in the soil were measured. The contribution of urea nitrogen was deducted by 15N isotope tracing to determine the amount of nutrients released by the rice straw itself. Urea nitrogen used to adjust the carbon-nitrogen ratio is recorded separately and is not included in the nutrient carry-over balance. Nutrients actually released from rice straw are included in the same cross-season nutrient carry-over ledger as the available nutrient balance for the next season's soybean fertilization. After the decomposition monitoring period ends, the independent sampling area is merged into the main planting area, and subsequent soybean fertilization is carried out according to the same fertilization plan as the main planting area. The isotope control sampling area is only used for isotope tracer measurements during the decomposition monitoring period and is not included in yield statistics.

[0031] S5: Before sowing soybeans, prepare soybean base fertilizer according to the nutrient balance carried over from rice straw. The base fertilizer only contains phosphorus and potassium fertilizer, molybdenum fertilizer and boron fertilizer, and does not contain nitrogen components. The nitrogen requirement of soybean seedlings is 50 kg / ha. The effective nitrogen balance carried over from rice straw in the nutrient carryover ledger is 43 kg / ha. The nitrogen application rate during the seedling stage is 7 kg / ha, which is 10% higher than the nitrogen requirement of soybean seedlings, i.e., 5 kg / ha. Apply 7 kg / ha. Spray potassium dihydrogen phosphate solution twice during the grain filling stage, with an interval of 7 days between the two sprays.

[0032] S6: After the crop rotation cycle ends, the model prediction value of the straw nutrient release dynamic curve is compared with the measured value of the same field. The measured value of the same field refers to the total cumulative nutrient release of straw calculated from the last straw bag sample taken from the independent sampling area after the end of the S1 monitoring period, after drying, weighing, and nutrient determination. The relative error between the two is 12%, corresponding to an adjustment of the nitrogen equivalent coefficient of 0.03. After adjustment, the nitrogen equivalent coefficient of the next cycle is 0.53, and the next cycle S2 is executed according to 0.53. This value is the adjusted value after self-correction by S6 and is still within the technical solution of the method of this invention. The explanation here is understood as follows: the technical requirement of 0.3~0.5 is the initial selected range. After self-correction by S6, the equivalent coefficient can fluctuate according to the adjustment range based on the initial range, and the upper limit of the fluctuation does not exceed 0.6. Example

[0033] The experimental site for this embodiment is located in a typical paddy soil planting area in Chuzhou City, Anhui Province, in the middle and lower reaches of the Yangtze River. The crop rotation pattern is mid-season rice-autumn soybean rotation.

[0034] S1: After the previous soybean harvest, crush the soybean stalks to an average length of 3.5cm, spread them evenly on the field surface, and apply a compound decomposing agent of Bacillus subtilis and Aspergillus niger with an effective live bacteria count of 230 million / g. The application rate is 22.5kg per hectare. After application, rotary tillage is carried out to mix the stalks evenly. The rotary tillage depth is 17cm, and the soil moisture is adjusted to 65% of the field capacity. An independent sampling area was set up, with an area of ​​4.2% of the field area, adjacent to the main planting area. During the decomposition monitoring period, the independent sampling area implemented the same straw return to the field, rotary tillage depth, soil moisture management and water management operations as the main planting area. No fertilization was carried out in the independent sampling area during the S1 decomposition monitoring period. Sampling was conducted regularly on days 1, 3, 5, 7, 14, 21, and 28 after the straw was returned to the field. Five sampling points were set up at each time point, and three parallel replicates were set up for each group of samples. Soil samples and straw bag samples were collected.

[0035] S2: Before rice transplanting, the local soil testing and fertilizer recommendation for conventional basal fertilizer nitrogen application is 128 kg / ha. The total nitrogen requirement for rice throughout its growth period is 256 kg / ha, the total phosphorus requirement is 96 kg / ha, and the total potassium requirement is 160 kg / ha. Based on the straw nutrient release dynamic curve obtained in S1, the extrapolation predicts that the nitrogen release from straw after transplanting to the tillering stage is 33 kg / ha, the phosphorus release is 9 kg / ha, and the potassium release is 38 kg / ha. The nitrogen equivalent coefficient is set independently as 0.4, the phosphorus equivalent coefficient is 0.5, and the potassium equivalent coefficient is 0.7. The basal fertilizer coefficient r is taken as 0.65. According to formula (Ⅰ), the actual nitrogen application of basal fertilizer is 170 kg / ha, which is 30% higher than the recommended nitrogen application of conventional basal fertilizer, i.e., 38.4 kg / ha. It is applied at 70 kg / ha. The actual phosphorus application rate of phosphate fertilizer is 59.5 kg / ha, which is 30% higher than the recommended phosphorus application rate of conventional base fertilizer, i.e., 19.2 kg / ha. It is applied according to 59.5 kg / ha. The actual potassium application rate of potash fertilizer is 69.4 kg / ha, which is 30% higher than the recommended potassium application rate of conventional base fertilizer, i.e., 28.8 kg / ha. It is applied according to 69.4 kg / ha. The nitrogen, phosphorus and potassium nutrient deduction processes are independent and do not interfere with each other.

[0036] S3: After rice transplanting, dynamic verification of straw nutrient release is completed 7 days before the tillering stage, jointing and booting stage, and grain filling stage. The verification is achieved by taking straw bag samples from independent sampling areas and measuring straw weight loss rate and nutrient content. Based on the nitrogen amount of topdressing recommended by local soil testing and formula fertilization for each growth stage, the actual nitrogen amount of topdressing is the product of the recommended nitrogen amount of topdressing for the current period and the measured nitrogen release of straw and nitrogen equivalent coefficient for the current period. The calculated value after deduction is not less than 10% of the recommended nitrogen amount of topdressing for the current period. Phosphorus and potassium fertilizers are deducted independently according to the same rules, and corresponding minimum guaranteed application amounts are set. The actual amount of fertilizer applied each time and the measured straw release amount are recorded in the ledger to form a nutrient carry-over ledger that is revised period by period.

[0037] S4: After rice harvest, rice straw is shredded to an average length of 3.5cm and directly returned to the field. Urea is applied to adjust the carbon-to-nitrogen ratio to 27:1, and the straw is rotary tilled to a depth of 17cm to mix it thoroughly. Soil moisture is adjusted to 60% of field capacity. During the decomposition monitoring period, the same amount and type of urea as in the main planting area is applied to the independent sampling area to adjust the carbon-to-nitrogen ratio. An additional 50m² area is set up within the independent sampling area. 2 The control area was treated with 15N-labeled urea with an abundance of 10 atom%, and the amount of 15N-labeled urea applied was the same as that of ordinary urea in the main area. Sampling was conducted on days 1, 3, 5, 7, 14, 21, and 28 after rice straw return to the field, with five sampling points at each time point. Each sample group was replicated three times. The decomposition rate of rice straw and available nutrients in the soil were measured. The contribution of urea nitrogen was deducted by 15N isotope tracing to determine the amount of nutrients released by the rice straw itself. Urea nitrogen used to adjust the carbon-nitrogen ratio was recorded separately and not included in the nutrient carry-over balance. The nutrients actually released by the rice straw were included in the same cross-season nutrient carry-over ledger as the available nutrient balance for the next soybean fertilization season. After the decomposition monitoring period, the independent sampling area was merged into the main planting area, and subsequent soybean fertilization was carried out according to the same fertilization plan as the main planting area. The isotope control sample area was only used for isotope tracing measurements during the decomposition monitoring period and was not included in yield statistics.

[0038] S5: Before soybean sowing, prepare soybean base fertilizer based on the nutrient balance carried over from rice straw. The base fertilizer should only contain phosphorus, potassium, molybdenum, and boron fertilizers, and no nitrogen components. The nitrogen requirement for soybean seedlings is 48 kg / ha. The effective nitrogen balance carried over from rice straw in the nutrient carryover ledger is 32 kg / ha, and the nitrogen application rate during the seedling stage is 16 kg / ha, which is 10% higher than the soybean seedling nitrogen requirement (4.8 kg / ha). Apply 16 kg / ha. Spray potassium dihydrogen phosphate solution twice during the grain-filling stage, with a 10-day interval between the two applications.

[0039] S6: After the crop rotation cycle ends, the model prediction value of the straw nutrient release dynamic curve is compared with the measured value of the same field. The measured value of the same field refers to the total cumulative nutrient release of straw calculated from the last straw bag sample taken from the independent sampling area after the end of the S1 monitoring period, after drying, weighing, and nutrient determination. The relative error between the two is 18%, exceeding 10% but not exceeding 20%, corresponding to an adjustment of the nitrogen equivalent coefficient of 0.04. After adjustment, the nitrogen equivalent coefficient for the next cycle is 0.44.

[0040] Example 3: The test site for this example is a typical paddy soil planting area in Jingzhou City, Hubei Province, and the crop rotation mode is early rice-summer soybean rotation.

[0041] S1: After the previous soybean harvest, crush the soybean stalks to an average length of 3cm and spread them evenly on the field surface. Apply a compound decomposing agent of Bacillus subtilis and Aspergillus niger with an effective live bacteria count of 240 million / g and an application rate of 20kg per hectare. After application, rotary tillage to mix the agent evenly to a depth of 16cm to adjust the soil moisture to 65% of the field capacity. An independent sampling area was set up, with an area of ​​3.8% of the field area, located inside the main planting area. During the decomposition monitoring period, the independent sampling area implemented the same straw return to the field, rotary tillage depth, soil moisture management and water management operations as the main planting area. No fertilization was carried out in the independent sampling area during the S1 decomposition monitoring period. Sampling was conducted regularly on days 1, 3, 5, 7, 14, 21, and 28 after the straw was returned to the field. Five sampling points were set up at each time point, and three parallel replicates were set up for each group of samples. Soil samples and straw bag samples were collected.

[0042] S2: Before rice transplanting, the recommended nitrogen application rate for conventional basal fertilizer based on local soil testing and fertilizer formulation is 120 kg / ha. The total nitrogen requirement for rice during its entire growth period is 240 kg / ha, the total phosphorus requirement is 90 kg / ha, and the total potassium requirement is 150 kg / ha. Based on the straw nutrient release dynamic curve obtained in S1, the extrapolated prediction of straw nitrogen release from transplanting to tillering stage is 60 kg / ha, phosphorus release is 15 kg / ha, and potassium release is 55 kg / ha. Nitrogen equivalent coefficients are independently set at 0.7, phosphorus equivalent coefficients at 0.6, and potassium equivalent coefficients at 0.8. The basal fertilizer coefficient r is set to 0.5, and calculated using formula (Ⅰ) to be 36 kg / ha. Therefore, 36 kg / ha is taken as the actual nitrogen application rate for basal fertilizer. The amount of straw nitrogen equivalent that could not be deducted from the base fertilizer was 18 kg / ha. This amount that was not deducted will be included in the cross-season nutrient carry-over ledger and will be deducted first in the topdressing during the S3 tillering stage after rice transplanting. Phosphate fertilizer: The recommended phosphorus content for conventional base fertilizer is 60 kg / ha, but the actual phosphorus application rate is 51 kg / ha, which is 30% higher than the recommended phosphorus content for conventional base fertilizer, i.e., 18 kg / ha. Apply 51 kg / ha. Potassium fertilizer: The recommended potassium application rate for conventional base fertilizer is 90 kg / ha, but the actual application rate is 46 kg / ha, which is 30% higher than the recommended amount, i.e., 27 kg / ha. The nitrogen, phosphorus, and potassium nutrient deduction processes are independent and do not interfere with each other.

[0043] S3: After rice transplanting, dynamic verification of straw nutrient release is conducted 5 days before the tillering, jointing-booting, and grain-filling stages. Based on the nitrogen application rates recommended by local soil testing and fertilizer application guidelines for each growth stage, the recommended nitrogen application rate for the tillering stage is 60 kg / ha. The actual measured nitrogen release from straw during the tillering stage is 25 kg / ha, with a nitrogen equivalent coefficient of 0.7. The deduction for the current period is 7.5 kg / ha. Subtracting the carryover deduction of 18 kg / ha recorded in S2, the calculated value is 24.5 kg / ha, which is 10% higher than the recommended nitrogen application rate for the current period (6 kg / ha). Therefore, 24.5 kg / ha is applied. The same rules apply to the jointing-booting and grain-filling stages. Each actual fertilizer application and measured straw release rate is recorded in a ledger, forming a nutrient carryover ledger that is updated periodically.

[0044] The operation steps of S4, S5, and S6 are the same as in Example 1. In S5, the nitrogen requirement of soybean seedlings is 45 kg / ha, the effective nitrogen balance of rice straw carried over in the nutrient carryover ledger is 40 kg / ha, and the nitrogen application rate during the seedling stage is 5 kg / ha, which is 10% higher than the nitrogen requirement of soybean seedlings, i.e., 4.5 kg / ha. Therefore, it is applied at 5 kg / ha. In S6, the relative error between the model prediction value and the measured value is 9%, which does not exceed 10%, so there is no need to adjust the parameters for the next cycle.

[0045] Comparative Example 1 This comparative study adopted existing fixed-ratio fertilizer reduction technology, and the experimental site and soil conditions were the same as in Example 1. After the previous crop soybean straw was crushed and returned to the field, no decomposing bacteria were applied, no independent sampling area was set up to monitor straw nutrient release, and fertilizer was applied at a uniform rate of 20% less than the conventional application rate throughout the entire crop rotation cycle. No cross-seasonal nutrient carry-over ledger was set up, and the fertilizer application rates for each growth stage of rice and soybean were reduced by a fixed ratio without dynamic verification. When rice straw was returned to the field, the urea nitrogen used to adjust the carbon-nitrogen ratio was directly included in the basal fertilizer nitrogen amount. Isotope tracing was not used to distinguish straw nitrogen from urea nitrogen, and the fertilizer parameters were not corrected after the crop rotation cycle ended.

[0046] Comparative Example 2 This comparative example uses existing single-season soil testing and fertilizer recommendation technology, and the experimental site and soil conditions are the same as in Example 2. Soil testing is conducted only once before the sowing of each crop, and the amount of fertilizer applied in that season is determined based on the soil nutrient content of that season. The utilization of straw is not differentiated, the carryover of nutrients from the previous crop's straw return to the field is not considered, straw nutrient release monitoring is not set up, and the amount of topdressing at each growth stage is applied according to fixed recommended values ​​without dynamic adjustment mechanism. The parameters are not iterated after the crop rotation cycle ends.

[0047] Core Experimental Data Table Table 1 Comparison of core nutrient parameters between each embodiment and the comparative example

[0048] The total fertilizer reduction rate in the four embodiments was more than 80% higher than that in the comparative example, the nitrogen fertilizer utilization rate was more than 30% higher, the straw nutrient calculation error rate was reduced to less than 10%, the cross-season nutrient carryover utilization rate was nearly doubled, and the incidence of seedling growth suppression and late-stage vegetative growth was less than 3%. This effectively solved the shortcomings of existing technologies, such as nutrient supply and demand mismatch, large straw nutrient calculation deviations, and cross-season nutrient waste. In Example 4, due to triggering the 30% lower limit protection for basal fertilizer, the undeducted amount was carried over to the topdressing period for further deduction. The total fertilizer reduction rate and nitrogen fertilizer utilization rate were the highest among the four embodiments, indicating that even with a large amount of straw release, this method can still achieve full nutrient deduction through periodic carryover. Comparative Example 1, due to the use of a fixed ratio of fertilizer reduction without matching the nutrient release rhythm, had a higher incidence of abnormal growth; Comparative Example 2 did not calculate the cross-season straw nutrient carryover, resulting in a lower nutrient utilization rate.

[0049] Table 2 Comparison of parameter adaptability for three consecutive seasons of crop rotation

[0050] In all four embodiments, the yield achievement rate remained stable at over 98% for three consecutive seasons, and the parameter adaptation deviation rate was less than 8%, effectively solving the shortcomings of existing technologies where parameters are fixed and long-term application adaptability gradually declines. Comparative Examples 1 and 2 did not have an annual self-correction mechanism. As the number of rotation seasons increased, the parameter adaptation deviation rate continued to rise, and the yield achievement rate decreased year by year, verifying the technical advantages of the self-correction mechanism of this invention.

[0051] refer to Figure 2 In all four embodiments, the yield compliance rate remained stable at over 98% for three consecutive seasons, and the parameter adaptation deviation rate was below 8%, effectively solving the shortcomings of existing technologies where parameters are fixed and long-term application compatibility gradually declines. Comparative Examples 1 and 2 did not have an annual self-correction mechanism. As the number of rotation seasons increased, the parameter adaptation deviation rate continued to rise, and the yield compliance rate decreased year by year, verifying the technical advantages of the self-correction mechanism of this invention.

[0052] refer to Figure 3 This figure clearly illustrates the differences in yield stability among different technical solutions within a continuous cropping rotation cycle. The yield achievement rate of the proposed solution remained consistently above 98% across all three seasons, without significant fluctuations. In contrast, the yield achievement rates of the two existing technologies decreased year by year with increasing cropping seasons, decreasing by 6.1 and 5.4 percentage points respectively in the third season compared to the first. This effectively verifies that the proposed solution, through its parameter self-correction mechanism after the cropping rotation cycle ends, addresses the shortcomings of existing technologies with fixed parameters and gradually declining long-term applicability. The dynamic parameter adjustment mechanism of this invention ensures long-term adaptability of the technical solution to different soil conditions and straw decomposition characteristics in various fields, maintaining stable yield performance without the need for large-scale soil testing annually, thus reducing long-term operational costs.

[0053] refer to Figure 4 This figure visually illustrates the differences in adaptability and growth regulation effects of different technical solutions. The parameter adaptation deviation rate of the present invention is reduced by 74% and 70% respectively compared to the two existing technologies; the incidence of seedling growth suppression is reduced by 85% and 79% respectively; and the incidence of late-stage vegetative growth and delayed maturity is reduced by 90% and 87% respectively. This effectively solves the defects of seedling growth suppression and late-stage vegetative growth and delayed maturity caused by nutrient supply and demand mismatch in existing technologies. The reduction in these three indicators verifies that the present invention, through techniques such as protecting the lower limit of basal fertilizer application and dynamically reviewing and deducting nutrients during the growth period, achieves precise matching between straw nutrient release and crop nutrient demand rhythm, avoiding abnormal crop growth problems caused by excessive or insufficient fertilization, and ensuring the stable yield of the rice-soybean rotation system.

[0054] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for co-cultivation of soybean-rice rotation in paddy soil or alluvial soil in the middle and lower reaches of the Yangtze River and the Huang-Huai region, using a cross-seasonal continuous nutrient carryover ledger as its core, and achieving nutrient offsetting by dynamically deducting the amount of chemical fertilizer from the nutrient equivalent released by straw, including the following steps: S1: Crush the previous crop soybean straw to a length of less than 5cm and spread it evenly. After applying the decomposing bacteria, till the soil to a depth of 15-20cm and adjust the moisture to 60%-70% of the field capacity. Regularly sample and measure the straw weight loss rate and the content of available nutrients in the soil. Fit the dynamic curve of straw nutrient release and calculate the release of nitrogen, phosphorus and potassium at each time period. S2: The amount of rice base fertilizer is the recommended amount of conventional base fertilizer multiplied by the base fertilizer coefficient (nitrogen 0.5~0.8), minus the predicted amount of fertilizer released by straw before the tillering period multiplied by the corresponding amount coefficient, of which nitrogen is 0.3~0.7, and phosphorus and potassium are set separately. The actual application amount is not less than 30% of the recommended amount of conventional base fertilizer. The undeducted part is recorded in the nutrient carry-over ledger. S3: At least 5 days before topdressing rice during the tillering, jointing and booting, and grain-filling stages, the actual fertilizer release from straw should be verified. The amount of topdressing should be the recommended amount for the current period minus the actual fertilizer release for the current period multiplied by the equivalent coefficient and then minus the corresponding carry-over deduction amount. The actual application amount should not be less than 10% of the recommended amount for the current period. The nutrient carry-over ledger should be updated period by period. S4: Rice straw is crushed to a length of less than 5cm and returned to the field. Urea is applied to adjust the carbon-nitrogen ratio to 25:1~30:

1. Urea nitrogen and nitrogen released from the straw itself are distinguished by isotope tracing. Urea nitrogen is recorded separately, and nitrogen released from the straw is included in the nutrient carry-over ledger for use in the next season's soybean fertilization. S5: Soybean base fertilizer contains only phosphorus and potassium fertilizer, molybdenum fertilizer and boron fertilizer, and no nitrogen. The amount of nitrogen applied during the seedling stage is the amount of nitrogen required by soybean seedlings minus the carryover effective nitrogen balance, and it shall not be less than 10% of the nitrogen required during the seedling stage. During the grain filling stage, phosphorus and potassium fertilizer shall be sprayed on the leaves according to the growth. S6: After the crop rotation cycle ends, the model equivalent coefficient and release rate parameters are corrected using the measured values ​​of straw nutrient release, so as to achieve self-correction year by year.

2. The method according to claim 1, characterized in that, The sampling time nodes mentioned in S1 and S4 all include days 1, 3, 5, 7, 14, 21 and 28 after returning straw to the field. There are no less than 5 sampling points at each time node, and each group of samples is set up with 3 parallel replicates. The dynamic curve of straw nutrient release is fitted by a Logistic model or an exponential decay model.

3. The method according to claim 1, characterized in that, The decomposing microbial agent described in S1 is a compound microbial agent of Bacillus subtilis and Aspergillus niger, with an effective viable count of not less than 200 million / g, and an application rate of 15kg~30kg per hectare.

4. The method according to claim 1, characterized in that, The equivalent coefficients of nitrogen, phosphorus, and potassium are set independently, with the equivalent coefficient of nitrogen being 0.3~0.5, the equivalent coefficient of phosphorus being 0.4~0.6, and the equivalent coefficient of potassium being 0.6~0.8; the equivalent coefficients for different growth stages and different straw types are set independently.

5. The method according to claim 1, characterized in that, Soil available nitrogen in S1 and S4 was determined by alkaline diffusion method, available phosphorus in soil was determined by Olsen method, and available potassium in soil was determined by ammonium acetate extraction flame photometry.

6. The method according to claim 1, characterized in that, When calculating the amount of fertilizer applied during each growth stage, the independent deductions for nitrogen, phosphorus, and potassium are calculated separately, and then summarized to form a complete fertilization plan for the current period. The deduction processes for different nutrients do not interfere with each other.

7. The method according to claim 1, characterized in that, In S4, after returning rice straw to the field, adjust the soil moisture to 55%~65% of the field capacity, and the rotary tillage depth is 15cm~20cm.

8. The method according to claim 1, characterized in that, The phosphorus and potassium fertilizer sprayed during the granulation stage of S5 is potassium dihydrogen phosphate solution, which is sprayed 1 to 2 times, with an interval of 7 to 10 days between the two sprays.

9. The method according to claim 1, characterized in that, When the error between the model prediction and the measured value in S6 exceeds 10%, the equivalent coefficient and release rate parameter of the nutrient type are adjusted accordingly, and the adjustment range is positively correlated with the error magnitude. Specifically, when the relative error is 10%~20%, the equivalent coefficient is adjusted by 0.02~0.05; when the relative error exceeds 20%, the equivalent coefficient is adjusted by 0.05~0.

10.

10. The method according to claim 1, characterized in that, The independent sampling area is set up in or adjacent to the main planting area, with an area of ​​not less than 3% of the field area. During the decomposition monitoring period, the straw return to the field amount, rotary tillage depth, soil moisture and water management are the same as those in the main planting area. During the monitoring period of soybean straw decomposition in S1, no fertilizer was applied to the independent sampling area. During the monitoring period of rice straw decomposition in S4, the same type and amount of urea as that in the main planting area was applied to the independent sampling area to adjust the carbon-nitrogen ratio. A control sampling area with isotope-labeled urea was set up inside the independent sampling area. After the decomposition monitoring was completed, the independent sampling area was merged into the main planting area, and subsequent fertilization was carried out according to the plan of the main planting area. The control sampling area was only used for isotope tracer measurement during the decomposition period and was not included in the yield statistics.

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