Straw returning-to-field water-nitrogen synergistic method based on biochemical inhibitor

Abstract

The invention discloses a straw returning water-nitrogen synergistic method based on a biochemical inhibitor, and belongs to the technical field of agricultural resources and environments. The straw returning water-nitrogen synergistic method based on the biochemical inhibitor comprises the following steps that in an annona squamosa-soybean interplanting system, a water-nitrogen synergistic agent is added into an annona squamosa-soybean interplanting system; the nitrogen release and straw decomposition process is regulated and controlled through the synergistic effect of the biochemical inhibitor and water management, short-term crop requirements and long-term soil fertilization are both considered, and the water and nitrogen utilization efficiency is improved. According to the invention, a comprehensive strategy of'regulation and control of nitrogen release by a biochemical inhibitor and collaborative management of water and nitrogen 'is adopted. Release of nitrogen fertilizer is delayed through the urease inhibitor, straw decomposition and crop requirements are matched, and short-term nitrogen starvation of soybeans is avoided; generation of nitrate nitrogen is reduced through the nitrification inhibitor, nitrogen leaching and denitrification loss are reduced, and the nitrogen fertilizer utilization rate is increased; the irrigation amount is adjusted according to the straw decomposition stage and the crop growth stage, microbial decomposition is driven, and meanwhile the carbon conversion efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of agricultural resources and environmental technology, and in particular relates to a method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors. Background Technology

[0002] In the custard apple-soybean intercropping system, returning soybean straw to the field after harvest is an important ecological management measure. This system offers advantages such as improved land utilization, reduced reliance on chemical fertilizers through soybean nitrogen fixation, and increased soil organic carbon from straw return. However, the high carbon-to-nitrogen ratio of the straw leads to intense competition for available nitrogen in the soil with custard apples and soybeans during decomposition, easily causing short-term "nitrogen starvation" in crops (especially soybeans), inhibiting growth and nitrogen fixation capacity. Furthermore, the nitrogen fertilizer traditionally applied to address this problem has low utilization rates during dry seasons or under uneven irrigation conditions, and is easily lost through nitrification and leaching, increasing both environmental risks and production costs. Simultaneously, soil moisture, a key driver of microbial decomposition and nutrient migration, lacks coordination with nitrogen fertilizer application, resulting in slow straw decomposition, low carbon conversion efficiency, and difficulty in achieving the expected goals of soil carbon sequestration and fertilization. Existing technologies mostly focus on the regulation of single factors, lacking a comprehensive method that can simultaneously optimize water and nitrogen conditions and precisely match crop-microbial needs to improve the benefits of straw return.

[0003] Therefore, there is an urgent need to develop an efficient management method based on biochemical inhibitors and synergistic regulation of water and nitrogen processes, which is crucial for solving the bottleneck of this intercropping system and achieving green agricultural development. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors includes the following steps:

[0007] In the fruit tree-leguminous crop intercropping system (custard apple-soybean intercropping system) in hilly areas, the release of nitrogen and the process of straw decomposition are regulated by the synergistic effect of biochemical inhibitors and staged water management, taking into account both short-term crop needs and long-term soil fertility, and improving water and nitrogen use efficiency.

[0008] Optionally, the specific steps of the straw return-to-field water and nitrogen synergistic method based on biochemical inhibitors are as follows:

[0009] (1) Mix biochemical inhibitors and nitrogen fertilizer evenly to obtain special nitrogen fertilizer, spread it on the straw layer, and then rotary till and bury it to achieve uniform mixing of straw, fertilizer and soil;

[0010] (2) Water management is carried out in stages, specifically as follows:

[0011] In the initial stage (0-20 days), maintain soil moisture at 70%-80% of field capacity to promote microbial decomposition and avoid nitrogen competition during the seedling stage;

[0012] During the mid-term (21-40 days), adjust the humidity to 60%-70% of field capacity, and apply nitrogen fertilizer according to the soil nitrate nitrogen monitoring results to meet the peak nitrogen requirement of soybean during the flowering period;

[0013] In the later stage (41-60 days), the humidity is reduced to 50%-60% of field capacity to slow down mineralization, promote organic carbon fixation, and utilize ammonium nitrogen for absorption by the custard apple root system.

[0014] Optionally, the biochemical inhibitor includes a urease inhibitor and a nitrification inhibitor, wherein the mass ratio of the urease inhibitor to the nitrification inhibitor is 1:2.

[0015] Beneficial Effects: This invention, through the synergistic effect of urease inhibitors and nitrification inhibitors combined with precise irrigation management, effectively regulates nitrogen conversion during straw return to the field. Urease inhibitors delay the hydrolysis of urea into ammonium nitrogen (NH4). + This reduces ammonia volatilization loss and provides a critical time window for subsequent nitrification inhibition; nitrification inhibitors, on the other hand, inhibit the activity of nitrite-oxidizing bacteria, controlling the conversion of ammonium nitrogen to nitrate nitrogen (NO3). - This process transforms nitrogen into a stable ammonium form with low mobility, making it less susceptible to leaching and denitrification. Based on this, precise irrigation in the initial stage provides suitable moisture for soil microorganisms, promoting the initiation of straw decomposition while preventing excessive moisture from causing inhibitors to become ineffective or nitrogen loss. In other words, this invention, through a three-pronged regulatory mechanism of "enzyme inhibition—nitrification control—water regulation," effectively retains nitrogen in the root zone soil. This satisfies the nitrogen source requirements for microbial straw decomposition, preventing competition for nitrogen during the crop seedling stage, and ensures that nitrogen is gradually released as microorganisms die during the later stages of straw decomposition. This achieves a highly efficient match between slow nutrient release and the growth needs of custard apples, significantly improving nitrogen fertilizer utilization efficiency and soil conservation effects.

[0016] Furthermore, the urease inhibitor includes N-butylthiophosphoric triamine (NBPT); the nitration inhibitor includes dicyandiamide (DCD).

[0017] Optionally, in the special nitrogen fertilizer, the mass ratio of biochemical inhibitor to nitrogen fertilizer is 1:100-150.

[0018] Optionally, the nitrogen fertilizer is urea (nitrogen content 46%), and the nitrogen application rate (N) is 80-120 kg·hm². -2 .

[0019] Optionally, the straw layer is laid on the soil surface between rows outside the drip line of the custard apple tree canopy, and the amount returned to the field is controlled at 6 t·hm. -2 .

[0020] Furthermore, the straw layer is obtained by mechanically crushing soybean straw, cutting it to a length of 5-10cm, and then laying it out.

[0021] Optionally, the thickness of the rotary tillage and burial is 0-20cm, and its thickness is not 0.

[0022] Optionally, the specific procedure for supplementing nitrogen fertilizer based on soil nitrate nitrogen monitoring results is as follows:

[0023] Real-time monitoring of nitrate nitrogen (NO3) in rotary tilled soil layers using soil available nitrogen sensors (such as ion-selective electrodes). - If the content is less than 10 mg / kg -1 (Critical value for soybean flowering period), supplement with 10%-20% of the special nitrogen fertilizer used in step (1).

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] This invention employs a comprehensive strategy of "biochemical inhibitor regulation of nitrogen release + synergistic water and nitrogen management." By using urease inhibitors to delay nitrogen fertilizer release, it matches straw decomposition with crop needs, avoiding short-term "nitrogen hunger" in soybeans. Nitrification inhibitors reduce nitrate nitrogen formation, decreasing nitrogen leaching and denitrification losses, thus improving nitrogen fertilizer utilization. Adjusting irrigation amounts according to the straw decomposition stage and crop growth period drives microbial decomposition while increasing carbon conversion efficiency, resulting in an 8.2%-11.6% increase in soil organic carbon content. This reduces water demand due to nitrogen fertilizer loss and ineffective irrigation, achieving multi-factor synergy among "straw-water-nitrogen-crop," enhancing the benefits of straw return to the field, and increasing crop yield by 9.2%-13.6%.

[0026] In summary, the method of this invention is simple, highly operable, and easily integrated with existing agronomic practices, facilitating its widespread application. This method provides a green, efficient, and replicable solution for straw return in the custard apple-soybean intercropping system, meeting the needs of green agricultural development. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] This invention discloses a method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors, comprising the following steps:

[0033] Step 1: Straw pretreatment and return to the field

[0034] 1. After harvesting soybeans between rows of custard apples, mechanically crush the soybean stalks and cut them to a length of 5-10cm;

[0035] 2. Spread the crushed straw evenly on the soil surface between rows outside the drip line of the custard apple tree canopy, and control the amount of straw returned to the field at 6 t·hm. -2 .

[0036] Step 2: Formulate a special nitrogen fertilizer containing biochemical inhibitors.

[0037] 1. Determine the total amount of basal nitrogen fertilizer: Based on the soil's basic fertility and target yield, allocate 40%-50% of the total nitrogen required for the soybean season as basal fertilizer; the basal fertilizer nitrogen application rate (N) is 80-120 kg·hm². -2 ;

[0038] 2. Use urease inhibitors, such as N-butylthiophosphoric triamine (NBPT), to inhibit soil urease activity, slow down the rate of urea hydrolysis to ammonia, and avoid ammonia volatilization loss;

[0039] 3. Use nitrification inhibitors, such as dicyandiamide (DCD), to inhibit the activity of nitrifying bacteria and reduce nitrate nitrogen (NO3). - This process generates nitrogen, reducing nitrogen leaching and denitrification losses.

[0040] 4. Use a compound formulation of urease inhibitor and nitrification inhibitor. The synergistic effect of the two can achieve the dual regulatory goal of "delaying nitrogen fertilizer release and reducing nitrogen loss".

[0041] Step 3: Co-application and tillage

[0042] 1. Mix the compound inhibitor and nitrogen fertilizer (conventional urea, nitrogen content 46%) in a dry environment at a mass ratio of inhibitor: nitrogen fertilizer = (1:100)-(1:150) to prepare a special nitrogen fertilizer for later use;

[0043] 2. Spread the prepared nitrogen fertilizer containing inhibitors evenly on the spread straw; perform rotary tillage or plowing (0-20cm soil) to take into account both the shallow root absorption of soybeans and the deep root needs of custard apples.

[0044] Step 4: Coordinated water and nitrogen irrigation: Matching straw decomposition with crop needs

[0045] Based on the straw decomposition stage and crop growth period, irrigation volume and timing are adjusted in stages to achieve a synergistic effect of "water-driven microbial decomposition + precise nitrogen fertilizer release":

[0046] Phase 1: Initial stage of straw decomposition (0-20 days) activates soil microorganisms and dissolves inhibitors, meeting the microorganisms' nitrogen requirements while ensuring soybean seedling growth.

[0047] 1. Control the irrigation amount to 70%-80% of field capacity (monitored by soil moisture sensor) to keep the soil moist and activate decomposing microorganisms;

[0048] 2. Due to the action of biochemical inhibitors, nitrogen loss is reduced, matching the nitrogen demand of microorganisms decomposing straw, and avoiding "nitrogen starvation" in soybean seedlings due to "nitrogen being competed for by straw".

[0049] Phase 2: Mid-stage of straw decomposition (21-40 days), accelerating straw decomposition while meeting the nitrogen requirements of soybean flowering (peak nitrogen demand) and custard apple growth.

[0050] 1. Adjust the irrigation amount to 60%-70% of field capacity to avoid excessive water causing nitrification inhibitors to become ineffective;

[0051] 2. Real-time monitoring of nitrate nitrogen (NO3) in the 0-20cm soil layer using soil available nitrogen sensors (such as ion-selective electrodes). - If the content is less than 10 mg / kg -1 (Critical value for soybean flowering period), supplement with 10%-20% of the initial amount of special nitrogen fertilizer to ensure that nitrogen supply matches crop demand.

[0052] Phase 3: Late stage of straw decomposition (41-60 days), complete straw decomposition (remaining amount ≤20%), promote soil organic carbon fixation.

[0053] 1. Reduce irrigation to 50%-60% of field capacity to decrease the rate of microbial decomposition and reduce the loss of organic carbon mineralization;

[0054] 2. Stop nitrogen fertilizer application and rely on the continuous action of biochemical inhibitors (nitrification inhibition period of about 60 days) to fix the remaining nitrogen into ammonium nitrogen (NH4). + This reduces leaching losses and provides a long-lasting nitrogen source for the deep root system of custard apples.

[0055] The urease inhibitor used in this invention works by delaying the hydrolysis of urea into ammonium nitrogen (NH4). + The rate of ammonia volatilization is reduced, minimizing ammonia volatilization loss and allowing nitrification inhibitors more time to act; nitrification inhibitors suppress the activity of nitrite-oxidizing bacteria, preventing the conversion of ammonium nitrogen to nitrate nitrogen (NO3). - The process of nitrogen conversion, maintaining it in an ammonium form that is less susceptible to leaching and denitrification, is achieved through precise initial irrigation that creates a suitable humidity environment for microbial decomposition of straw. Inhibitors guide nitrogen conversion, preventing volatilization, leaching, and denitrification, and extending nitrogen retention time in the soil. This allows the nitrogen temporarily held by microorganisms to be released more efficiently during later decomposition and aging, and then absorbed and utilized by the custard apple tree.

[0056] All raw materials used in this invention were purchased from the market.

[0057] The technical solution of the present invention will be further illustrated by the following embodiments.

[0058] Example 1

[0059] A method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors includes the following steps:

[0060] 1. Preparation of straw

[0061] After soybeans mature and are harvested, the seeds are removed, and the straw is crushed to 5-10cm using a straw crusher (this can be achieved by adjusting the screen mesh size of the crusher). The coefficient of variation of straw length after crushing is ≤15%.

[0062] 2. Preparation of a biochemical inhibitor-nitrogen fertilizer composite system

[0063] A composite inhibitor was prepared by mixing the urease inhibitor N-butylthiophosphoric triamine (NBPT) and the nitration inhibitor dicyandiamide (DCD) at a mass ratio of NBPT:DCD = 1:2. The composite inhibitor was then added to conventional urea at a mass ratio of 1:125 and stirred for 10 minutes using a drum mixer (30 rpm) to ensure uniform adhesion of the inhibitor to the urea granules. When using only a single inhibitor (NBPT or DCD), the mass ratio of inhibitor to nitrogen fertilizer was maintained at 1:125, and the remaining procedures were the same. The mixed "inhibitor-nitrogen fertilizer composite system" was packaged into breathable woven bags and stored in a cool, dry place at a temperature ≤25℃ and humidity ≤60% to prevent moisture absorption. The shelf life is 6 months.

[0064] 3. The experimental site was a five-year-old custard apple orchard in Mangfei Village, Aihua Town, Yunxian County, Lincang City, Yunnan Province. The experiment was conducted in the second year after the custard apple seedlings were planted. The soil texture of the experimental orchard was sandy loam, and the soil organic carbon (SOC) was 15.74 g·kg⁻¹. -1 , bulk density 1.41 g·cm³ -3 The field capacity (FC) was 34.88%, the pH was 6.28, and the electrical conductivity was 0.58 mS·cm. -1 The soil ammonium nitrogen content was 31.68 mg·kg⁻¹. -1 The nitrate nitrogen content is 42.81 mg·kg⁻¹. -1 The soil microbial biomass nitrogen content was 98.36 mg·kg⁻¹. -1 Nitrogen fertilizer (conventional urea, containing 46% N) 80-120 kg / hm² -2 Phosphate fertilizer (P2O5) 78 kg·hm -2 Potassium fertilizer (K2O) 105 kg·hm -2 The amount of straw returned to the field is uniformly set at 6 t·hm. -2 .

[0065] The experimental garden uses drip irrigation as the conventional irrigation method, with irrigation scheduled daily from 8:00 to 10:00 AM, each irrigation lasting 2 hours. After irrigation, the target soil volumetric water content (VWC) of the 0-20cm soil layer is controlled at 60%-70% of field capacity, and is not adjusted based on the straw decomposition stage or crop growth period. Irrigation is carried out once every 7 days. If rainfall occurs (daily rainfall ≥ 20mm), the irrigation period is postponed by 1-2 days until the top 0-5cm soil layer is slightly dry before resuming the original irrigation cycle; there is no dynamic adjustment logic. The rated flow rate is 2.0 L·h. -1 The dripper has a single irrigation volume of 16.67m³. 3 ·hm -2 The spacing between drippers is matched with the row spacing of soybeans, with two drippers corresponding to each custard apple plant to ensure even water distribution.

[0066] Three control groups and three experimental groups were set up:

[0067] Control T1: No biochemical inhibitors were added, and water management was carried out using conventional irrigation, with an N application rate of 120 kg·hm². -2 Conventional irrigation, straw return to the field, fertilizer spread on the straw, rotary tillage and burial;

[0068] Control T2: The difference from Example 1 is that no biochemical inhibitors are added; that is, its nitrogen application rate is 80 kg·hm. -2 Irrigation in stages: 50%-80% field water holding capacity, straw returned to the field, fertilizer spread on the straw, rotary tillage and burying;

[0069] Comparison T3: The difference from Example 1 is that the phased water management is replaced with conventional irrigation, i.e., the nitrogen application rate is 80 kg·hm². -2 +NBPT+DCD, conventional irrigation, straw return to the field, fertilizer (biochemical inhibitor-nitrogen fertilizer compound system) is spread on the straw, rotary tillage and burial;

[0070] Experiment T4: i.e., Example 1, with an N application rate of 80 kg·hm². -2 +NBPT+DCD staged irrigation: field water holding capacity 50%-80%, straw returned to the field, fertilizer (biochemical inhibitor-nitrogen fertilizer compound system) spread on the straw, rotary tillage and burying;

[0071] Experiment T5: N application rate was 80 kg·hm -2 +NBPT staged irrigation: field water holding capacity 50%-80%, straw returned to the field, fertilizer (urease inhibitor-nitrogen fertilizer compound system) spread on the straw, rotary tillage and burying;

[0072] Experiment T6: N application rate was 80 kg·hm -2 +DCD phased irrigation: field water holding capacity 50%-80%, straw returned to the field, fertilizer (nitrification inhibitor-nitrogen fertilizer compound system) spread on the straw, rotary tillage and burying.

[0073] Each treatment was repeated three times, in a randomized manner, and 120m samples were selected from each experimental group. 2Each plot is considered a separate plot, with a minimum spacing of 4 meters between plots. The planting row spacing for custard apples is 4m x 3m. The soybean variety "Dian Dou No. 7" is selected and intercropped between the fruit tree rows. Sowing rows are 40cm wide, with a row spacing of 30cm and a plant spacing of 60cm, with 3 seeds per hole. Each plot is equipped with 1-2 soil moisture monitoring devices. Sensors should be buried in the main root layer of soybeans (0-20cm depth) and the active root layer of custard apples (20-40cm depth) to monitor soil volumetric water content (VWC) in real time. The core of phased irrigation is to control the soil moisture content in the 0-20cm soil layer within the target range based on the straw decomposition stage and crop water requirements. Before soybean sowing, representative points are selected between the custard apple rows, and 40-mesh nylon mesh bags containing 100g of crushed straw are buried 20cm deep in the experimental soil layer. Within each experimental plot, 15 replicate mesh bags were set up for each treatment (to provide replicate samples for the three decomposition stages). Sampling was carried out on days 21, 42, and 63, and after soybean harvest. Five replicate mesh bags were randomly selected from each treatment each time. After the samples were washed and dried, the dry matter weight of the residual straw was measured. The straw residue rate and decomposition rate were determined by the loss on weight method. The results are shown in Table 2.

[0074] 4. Phased precision irrigation

[0075] Phase 1: Activation of Decomposition and Seedling Promotion (Early Stage of Decomposition)

[0076] Create a high-humidity environment to fully activate the soil microbial community, initiate the straw decomposition process, and simultaneously ensure soybean emergence and seedling growth. Maintain the VWC (Volatile Water Content) of the 0-20cm soil layer at 70%-80% of field capacity (FC). Specific values: FC * 70% = 34.88% * 0.7 ≈ 24.4%; FC * 80% = 34.88% * 0.8 ≈ 27.9%. When the soil moisture content drops below 24.4%, immediately activate the drip irrigation system for supplemental irrigation until the moisture content reaches approximately 27.9%. Keep the soil moist during this stage.

[0077] Phase Two: Continuous Decomposition and Critical Water Demand Period (Mid-Stage Decomposition)

[0078] Maintaining suitable microbial activity continues to promote straw decomposition, while simultaneously meeting the substantial water requirements of soybeans during the flowering and podding stage (critical water requirement period), ensuring the number of effective pods and grains. Maintain the VWC (Volatile Water Content) of the 0-20cm soil layer at 60%-70% of field capacity (FC). FC * 60% = 34.88% * 0.6 ≈ 20.9%; FC * 70% = 34.88% * 0.7 ≈ 24.4%. Irrigation should begin when VWC falls below 20.9% and continue until it reaches approximately 24.4%. Water is crucial at this stage, and drought must be strictly prevented.

[0079] Phase Three: Completion of Decomposition and Moisture Control Period (Late Decomposition)

[0080] Most of the straw has decomposed. At this stage, it is necessary to reduce microbial activity, minimize the loss of mineralized organic carbon, and promote the formation of stable organic matter. Maintain the VWC (Very Water Content) of the 0-20cm soil layer at 50%-60% of the field capacity (FC). FC * 50% = 34.88% * 0.5 ≈ 17.4%; FC * 60% = 34.88% * 0.6 ≈ 20.9%. Only perform small-scale supplemental irrigation when the VWC falls below 17.4% to restore it to 20.9%, avoiding excessive irrigation.

[0081] Table 1. Soil physicochemical properties and organic carbon content after soybean harvest.

[0082]

[0083]

[0084] As shown in Table 1, soil acidification was most severe under treatment T1, with soil pH decreasing by 5.57% compared to the initial soil pH. The soil pH changes were smaller from treatment T2 to T6 (0.06-0.22). Under the combined effects of inhibitors and water, treatment T4 was significantly better than treatment T3, indicating a significant synergistic effect between optimized water management and biochemical inhibitors.

[0085] The conductivity under treatments T1, T3, and T4 increased by 36.2%, 31.0%, and 29.3% respectively compared to the initial value, indicating that the traditional high-nitrogen mode led to severe salt accumulation. Treatments T3 to T6 effectively retained nitrogen and prevented nutrient leaching under the action of inhibitors, while treatment T2 increased by 17.2% compared to the initial value.

[0086] The soil organic carbon content in treatment T4 was significantly higher than that in other treatments, increasing by 8.2% compared to treatment T1; under combined inhibitor and water-nitrogen synergistic management, the soil organic carbon content increased by 11.6%.

[0087] Table 2. Residual rate and decomposition rate of straw

[0088]

[0089] As shown in Table 2, the T5 treatment (NBPT only) delayed urea hydrolysis, resulting in a slightly more gradual and sustained nitrogen supply compared to T2. Its decomposition rate was slightly better than T2 but far inferior to T6. In the T6 treatment, DCD directly inhibited nitrification, storing nitrogen in the soil as ammonium nitrogen for an extended period, leading to a significantly faster decomposition rate than T5. The synergistic effect of NBPT and DCD (T3 and T4) was superior to either single agent, ensuring a stable and slow release of nitrogen fertilizer, providing a continuous and sufficient nitrogen source for microorganisms. The staged irrigation of the T4 treatment not only created the optimal microbial activation environment in the early stages but also prevented DCD deactivation due to excessive moisture in the middle stages (DCD typically lasts 30-60 days in the soil). In the later stages, water control retained nitrogen and carbon in the soil. The combination of these two treatments created the most ideal living environment for straw-decomposing microorganisms throughout the entire cycle, resulting in the fastest straw decomposition rate and the lowest residue rate.

[0090] Table 3. Changes in soil nutrients

[0091]

[0092]

[0093] As shown in Table 3, the T4 treatment consistently maintained the highest ammonium nitrogen content and the smallest, most stable nitrate nitrogen content. Through the synergistic effect of the combined inhibitor and moisture management, NBPT effectively mitigated the hydrolysis of urea, DCD effectively inhibited the activity of nitrite-oxidizing bacteria, and significantly delayed the degradation of NH4+. + To NO3 - The transformation process. Treatment T6 (DCD only) was superior to treatment T5 (NBPT only), indicating that in straw return systems, inhibiting nitrification is more important than simply delaying hydrolysis for maintaining the soil nitrogen pool. Furthermore, staged irrigation creates a more efficient and stable working environment for DCD (avoiding rapid degradation of DCD due to anaerobic conditions), thus most of the applied nitrogen fertilizer is converted into NH4+. + The nitrogen is retained in the soil in its original form, reducing nitrogen leaching loss.

[0094] The soil microbial biomass nitrogen (MBN) fixation in treatment T4 was significantly higher than in other treatments, indicating that the microbial community was in a nitrogen-sufficient and environmentally stable state. Treatment T4, building upon treatment T3, incorporated water management, which produced a strong synergistic effect with inhibitors, further optimizing MBN dynamics. Treatments T1 and T2 experienced dramatic increases and decreases in MBN, reflecting the drastic fluctuations between nitrogen enrichment and nitrogen starvation in the microorganisms, indicating unstable nitrogen supply.

[0095] Table 4 Soybean Yield and Quality

[0096]

[0097] As shown in Table 4, the T4 treatment, which involved compound inhibitors and water and nitrogen treatment, yielded the highest soybean yield, at 3185.46 kg·hm². -2 Compared to treatments T1 and T2, yields increased by 13.6% and 9.2%, respectively. Through the synergistic effect of water and nitrogen, the treatment precisely matched the growth needs of soybeans, achieving both increased yield and improved quality.

[0098] Table 5 Nitrogen Fertilizer Utilization Rate

[0099]

[0100] Table 5 shows that, under the premise of reducing nitrogen by 40%, the partial productivity of nitrogen fertilizer was significantly improved, especially in treatment T4, which reached the maximum partial productivity (41.07), an increase of 10.0% and 9.1% compared with the single inhibitor treatments (T5 and T6), respectively. Treatment T1 had the lowest agronomical utilization rate of nitrogen fertilizer (3.75), indicating that the applied nitrogen fertilizer had a poor yield-increasing effect and most of the nitrogen fertilizer was wasted. The agronomical utilization rate of nitrogen fertilizer in treatment T4 was significantly increased compared with T1 and T2, indicating that the synergistic effect of compound inhibitors and water and nitrogen can maximize the yield-increasing effect of fertilizer nitrogen.

[0101] Table 6. Nitrogen nutrition status of leaves in custard apple trees intercropped with soybeans.

[0102]

[0103] Table 6 shows that the T4 treatment had the best nitrogen nutrition status in the leaves during both the spring shoot emergence period and the late summer shoot maturation period of custard apples. The T3 and T4 treatments, due to the nitrogen-retaining effect of the inhibitors, enabled custard apples to obtain a more sufficient nitrogen supply during the spring shoot growth period, while soybeans were at their peak nitrogen fixation period during summer shoot growth, releasing a large amount of nitrogen into the soil. The T4 treatment, through water-nitrogen synergy, maximized the retention of nitrogen from soybean nitrogen fixation in the soil for absorption by the fruit trees.

[0104] In summary, this invention addresses the core bottlenecks of existing straw return technologies, such as aggravated nitrogen fixation, severe nitrogen loss, and a mismatch between water and nitrogen supply and demand. Through a synergistic design of using a compound biochemical inhibitor (NBPT+DCD) to regulate nitrogen conversion and staged irrigation, it achieves a dynamic match between the straw decomposition process and crop nitrogen requirements. Compared to single inhibitors or traditional straw return technologies, the compound inhibitor significantly improves nitrogen use efficiency, effectively reduces nitrogen loss, accelerates straw decomposition, and increases soil organic carbon content, achieving the dual benefits of increased soybean yield and improved nitrogen content in custard apple leaves.

[0105] This invention is the first to integrate biochemical inhibitor regulation with staged water and nitrogen management into a straw return system, solving the key problems of "nitrogen grabbing" and "nitrogen leakage" in traditional straw return systems. It boasts significant advantages such as ease of operation, environmental friendliness, and increased yield and quality. Applicable to fruit-leguminous crop intercropping systems in hilly areas of southern China and other straw return scenarios, it provides feasible technical support for straw resource utilization and green agricultural development, and has promising prospects for widespread application. Future research can further validate its continuous soil fertility improvement effect through long-term field trials, or combine it with an IoT-based intelligent irrigation system to achieve precise water and nitrogen management, thus expanding the scope of application.

[0106] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors, characterized in that, Includes the following steps: In the intercropping system of fruit trees and legumes in hilly areas, the release of nitrogen and the process of straw decomposition are regulated by the synergistic effect of biochemical inhibitors and staged water management, which takes into account both short-term crop needs and long-term soil fertility, and improves water and nitrogen use efficiency.

2. The method for synergistic water and nitrogen utilization of straw return to the field based on biochemical inhibitors according to claim 1, characterized in that, The steps are as follows: (1) Mix biochemical inhibitors and nitrogen fertilizer evenly to obtain special nitrogen fertilizer, spread it on the straw layer, and then rotary till and cover it; (2) Phased water management, the specific operation is as follows: During the initial 0-20 day period, maintain soil moisture at 70%-80% of field capacity; During the mid-term stage of 21-40 days, adjust the humidity to 60%-70% of field capacity, and apply special nitrogen fertilizer according to the soil nitrate nitrogen monitoring results; During the later stage of 41-60 days, the moisture content was reduced to 50%-60% of field capacity.

3. The method for synergistic water and nitrogen utilization of straw return to the field based on biochemical inhibitors according to claim 2, characterized in that, The biochemical inhibitors include urease inhibitors and nitrification inhibitors, and the mass ratio of the urease inhibitors to the nitrification inhibitors is 1:

2.

4. The method for synergistic water and nitrogen utilization of straw return to the field based on biochemical inhibitors according to claim 3, characterized in that, The urease inhibitor includes N-butylthiophosphoric triamine; The nitration inhibitor includes dicyandiamide.

5. A method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors according to claim 2, characterized in that, In the special nitrogen fertilizer, the mass ratio of biochemical inhibitor to nitrogen fertilizer is 1:100-150.

6. The method for synergistic water and nitrogen utilization of straw return to the field based on biochemical inhibitors according to claim 5, characterized in that, The nitrogen fertilizer mentioned is urea, and the application rate is 80-120 kg·hm². -2 .

7. The method for synergistic water and nitrogen utilization of straw return to the field based on biochemical inhibitors according to claim 2, characterized in that, The straw layer is laid on the soil surface between rows outside the drip line of the fruit tree canopy, with the amount of straw returned to the field controlled at 6 t·hm. -2 .

8. A method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors according to claim 7, characterized in that, The straw layer is obtained by mechanically crushing soybean straw, cutting it to a length of 5-10cm, and then laying it out.

9. A method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors according to claim 2, characterized in that, The thickness of the rotary tillage and burial is 0-20cm, and the thickness is not 0.

10. A method for synergistic water and nitrogen utilization in straw return to the field based on biochemical inhibitors according to claim 2, characterized in that, The specific procedure for supplementing nitrogen fertilizer based on soil nitrate nitrogen monitoring results is as follows: The nitrate nitrogen content in the rotary tilled and buried soil layer was monitored in real time using a soil available nitrogen sensor, and was below 10 mg·kg⁻¹. -1 When necessary, supplement with 10%-20% of the amount of special nitrogen fertilizer used in step (1).

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