A tillage method for coordinating nitrogen loss reduction in red soil dry slope land

Abstract

The application belongs to the technical field of agricultural water and soil conservation and environmental protection, and provides a kind of red soil dry slope nitrogen loss coordinated emission reduction tillage method. A three-section coordinated emission reduction system of source reduction-process blocking-control terminal management is established, dynamic control is implemented according to the quantitative contribution rate of nitrogen loss path and rainfall type, and the coordinated emission reduction of water, nitrogen and gas is realized through the weight dynamic distribution mechanism; the source reduction link takes reducing nitrogen input and optimizing nitrogen form as the core, controls the total amount of nitrogen entering the environment from the source through nitrogen reduction control, biochar application and deep fertilization; the process blocking link takes intercepting the lost nitrogen as the core, sets multiple blocking barriers in the nitrogen migration process through the coupling configuration of ecological ridge, plant hedge and straw mulching; the terminal management link takes nitrogen purification and reuse as the core, collects and processes slope runoff through the pit-constructed wetland system, and realizes the final purification and resource utilization of nitrogen.

Description

Technical Field

[0001] This invention belongs to the field of agricultural soil and water conservation and environmental protection technology, and in particular relates to a tillage method for coordinated reduction of nitrogen loss on dry red soil slopes. Background Technology

[0002] Red soil dry slopes are an important agricultural resource in the hilly areas of southern my country, mainly distributed in Hunan, Jiangxi, Guangxi, and Fujian provinces. Rainfall is concentrated and often heavy, and the soil is heavy and has poor porosity. Combined with the prevalence of traditional downslope farming, this leads to serious water and nitrogen loss and atmospheric nitrogen emissions in agricultural production. On the one hand, surface runoff from rainfall carries large amounts of nitrogen into water bodies, causing eutrophication of rivers and lakes. On the other hand, nitrogen fertilizer application exacerbates ammonia volatilization (NH3) and nitrous oxide (N2O) emissions, reducing nitrogen fertilizer utilization and increasing the risk of greenhouse effect and air pollution. Therefore, controlling nitrogen loss from red soil dry slopes has become a key focus of agricultural non-point source pollution control and ecological protection in this region.

[0003] Nitrogen loss in red soil dry slopes is characterized by complex pathways, diverse forms, and significant water-air coupling. Regarding aqueous nitrogen, nitrogen migrates into surface water bodies both as particulate and dissolved matter via surface runoff and eroded sediment, and also as nitrate nitrogen (NO3) through lateral seepage and deep percolation within the soil. — Nitrogen (NH3) is primarily lost to groundwater through leaching; as for gaseous nitrogen, nitrogen fertilizer applied to the soil enters the atmosphere through ammonia volatilization (NH3) and nitrous oxide (N2O) emissions. More importantly, there is a trade-off relationship among these multiple loss pathways: measures to reduce aqueous nitrogen loss may exacerbate gaseous nitrogen emissions, while measures to suppress gaseous nitrogen emissions may promote aqueous nitrogen leaching.

[0004] Existing nitrogen loss control technologies for red soil slopes mostly focus on optimizing a single pathway or a single link, which has the following shortcomings: (1) Technologies that focus on controlling water nitrogen loss (such as straw mulching and plant hedges) can reduce nitrogen loss carried by surface runoff and sediment, but long-term mulching may increase nitrogen leaching loss, and the decomposition of mulch may increase ammonia volatilization and N2O emissions; (2) Technologies that focus on reducing gaseous nitrogen emissions (such as optimized fertilization methods and slow-release fertilizers) can reduce ammonia volatilization, but their effect on controlling seepage loss is limited; (3) There is a lack of effective connection between engineering measures, plant measures and agronomic measures, making it difficult to form a full-chain coupled linkage mechanism of source reduction-process control-end treatment, and thus failing to achieve coordinated reduction of water nitrogen and gaseous nitrogen. Therefore, it is urgent to construct a farming method that covers the entire chain and coordinates multiple processes to achieve coordinated reduction of water nitrogen and gaseous nitrogen and stable crop yield and income increase in dry red soil slopes. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a cultivation method for coordinated reduction of nitrogen loss on dry red soil slopes, aiming to solve the problems mentioned in the background art.

[0006] This invention provides a tillage method for coordinated reduction of nitrogen loss on dry red soil slopes, including: establishing a three-stage coordinated emission reduction system of source reduction, process control and end-of-pipe treatment; implementing dynamic regulation based on the quantitative contribution rate of nitrogen loss pathways and annual rainfall patterns; and achieving coordinated emission reduction of water nitrogen and gaseous nitrogen through a weighted dynamic allocation mechanism. The source reduction, process control, and end-of-pipe treatment stages are as follows: The source reduction process focuses on reducing nitrogen input and optimizing nitrogen forms. Through nitrogen reduction regulation, biochar application, and deep fertilization, the total amount of nitrogen entering the environment is controlled at the source. The process control link focuses on intercepting and retaining lost nitrogen. Through the coupled configuration of ecological ridge cultivation, plant hedges and straw mulch, multiple control barriers are set up during nitrogen migration. The end-of-pipe treatment process focuses on nitrogen purification and reuse, using a pond-constructed wetland system to collect and treat slope runoff, thereby achieving the final purification and resource utilization of nitrogen.

[0007] Furthermore, in nitrogen reduction regulation, the mass ratio of base fertilizer to topdressing is 3:2, and topdressing is applied by hole application and covering with soil.

[0008] Furthermore, in the application of biochar, the hydroxyl groups on the surface of the biochar are directionally regulated and chemically cross-linked, including: the biochar is pyrolyzed under limited oxygen at 500℃ with a heating rate of 10℃ / min and a holding time of 2 hours to obtain biochar with hydroxyl groups directionally regulated; the biochar with hydroxyl groups directionally regulated is mixed with polyurethane at a mass ratio of 1:0.1-0.8 and mixed for 10-15 minutes to form a premix, which is then applied to the soil.

[0009] Furthermore, in the surface barrier layer, after sowing and before emergence, the premix is ​​applied to the ridge surface in conjunction with straw mulch, with a biochar:polyurethane mass ratio of 1:0.1~0.2; in the rhizosphere adsorption layer, the premix is ​​applied simultaneously with the basal fertilizer, at a depth of 10~15cm, with a biochar:polyurethane mass ratio of 1:0.2~0.3; in the deep permeability barrier layer, the premix is ​​applied during land preparation and ridging, at a depth of 15~25cm, with a biochar:polyurethane mass ratio of 1:0.5~0.8.

[0010] Furthermore, through the coupled configuration of ecological ridge cultivation, plant hedges, and straw mulch, multiple barriers are established during nitrogen migration, specifically: Ecological ridge cultivation: Construct a ridge and furrow system along the contour lines on the slope, with a ridge width of 60-80cm, a ridge height of 10-20cm, and a furrow depth of 10-15cm; Plant hedges: Perennial daylily hedges are laid along contour lines in sloping farmland, with a width of 60cm. The spacing between hedges is dynamically adjusted according to the slope: 10m when the slope is <10° and 8m when the slope is 10°~20°. Straw mulching: The amount of straw mulching is 3000~4500 kg / hm², and the mulching thickness is 3~5 cm.

[0011] Furthermore, the red soil dry slopes are planted with peanut-rapeseed rotation or corn-legume intercropping.

[0012] Furthermore, process control measures also include simplified no-till farming combined with inter-row cultivation and hilling, specifically: In peanut-rapeseed rotation, after the rapeseed crop is harvested, the soil is not turned over. Peanuts are sown in holes along the original contour ridges, with two rows per ridge. The ridges are 64 cm wide, 10 cm high, and the furrows are 20 cm wide and 15 cm deep. The row spacing is 32 cm and the hole spacing is 15 cm. The sowing depth is 4-5 cm. During the flowering and pegging stage of peanuts, the soil is cultivated and hilled up to increase the ridge height to 13-15 cm. Before rapeseed sowing or during the winter fallow and wet period, the ridge surface is cultivated to a depth of 15-20 cm to improve the compaction of the red soil. Deep cultivation is not carried out during periods of little rain and drought.

[0013] Furthermore, the pit-constructed wetland system specifically refers to: In the catchment area at the foot of the slope, pits and ponds are utilized or constructed according to local conditions. Artificial wetlands are built downstream of the outlet of the pits and ponds. The hydraulic retention time of the artificial wetlands is 3 to 5 days. Aquatic plants are planted. The wetland substrate uses a combination of gravel and biochar, with the biochar mixing ratio being 10% to 15% of the filler volume.

[0014] Furthermore, dynamic regulation is implemented based on annual rainfall patterns to establish a targeted prevention and control strategy for coordinated reduction of water nitrogen and gaseous nitrogen emissions. This is achieved through a dynamic weight allocation mechanism to coordinate the reduction of water nitrogen and gaseous nitrogen losses. Specifically, this includes the following steps: (1) The percentage anomaly P of the baseline precipitation value 30 years before peanut planting a Classification of year types: P a ≥20% is considered a wet year, P a A year with a water level ≤-20% is considered a dry year. <P a <20% is considered a normal water year; (2) Based on the measured range of apparent nitrogen loss rate in different water types (4.38%~22.17%), the basic weight W for nitrogen emission reduction in high-water years was set. w =0.65, average annual W w =0.50 and dry year W w =0.35, corresponding to the basic weight W for nitrogen emission reduction. a =1-W w .

[0015] Furthermore, differentiated regulation is implemented based on the nitrogen loss characteristics at different growth stages. Specifically: during the basal fertilizer stage, the focus is on reducing seepage and leakage by deep application of basal fertilizer to reduce the direct contact area between fertilizer and surface water; during the topdressing stage, the focus is on reducing runoff and preventing erosion by using hole or trench application methods to reduce the risk of fertilizer loss with surface runoff, while straw mulching is used to enhance surface protection; during the fallow period after harvest, the focus is on residual nitrogen management by planting green manure or mulching measures to reduce direct erosion of the topsoil by rainfall and prevent residual nitrogen from being lost with runoff and seepage during the non-growing season.

[0016] The present invention has the following technical effects: (1) Establish a three-stage coordinated emission reduction system of source reduction, process control and end treatment. The source reduction, process control and end treatment links are interconnected and work together. Among them, source reduction reduces the pressure of process control and end treatment; process control intercepts nitrogen that is not controlled by source reduction; end treatment treats nitrogen that is not intercepted by source reduction and process control; through system optimization of the whole chain, comprehensive emission reduction of nitrogen loss is achieved.

[0017] (2) Modified biochar achieves synergistic emission reduction of water nitrogen and gaseous nitrogen through physical adsorption, chemical cross-linking slow release, biological regulation and pH buffering. Specifically, the well-developed pore structure adsorbs nitrate nitrogen and reduces deep leaching; the biochar-polyurethane cross-linking network slows down the fertilizer release rate, reduces the instantaneous peak concentration of nitrogen in the soil solution, and reduces the risk of runoff scouring and leaching; inhibits the activity of nitrifying bacteria and reduces N2O emissions; and alleviates soil pH fluctuations after fertilization and reduces NH3 volatilization.

[0018] (3) Through the mutual coupling and hierarchical progression of the weight allocation of rainfall year type, precise regulation of the reproductive period and precise configuration based on the contribution rate of nitrogen loss pathway, a complete decision chain of weight assignment → path decomposition → parameter implementation is formed, so that the technical configuration not only meets the macro requirements of rainfall year type, but also accurately matches the nitrogen loss characteristics of each period and pathway, and realizes the systematic and coordinated emission reduction of water nitrogen and gas nitrogen loss. Attached Figure Description

[0019] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures: Figure 1 The TN concentrations of surface runoff and infiltration in peanut fields under different nitrogen application levels in Example 1 of this invention are shown.

[0020] Figure 2 This refers to the nitrogen output flux of peanut fields under different nitrogen application levels as a function of surface runoff and infiltration in Example 1 of the present invention. Detailed Implementation

[0021] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0023] This invention provides a tillage method for coordinated reduction of nitrogen loss on dry red soil slopes, comprising: Establish a three-stage coordinated emission reduction system consisting of source reduction, process control, and end-of-pipe treatment. Implement dynamic regulation based on the quantitative contribution rate of nitrogen loss pathways and annual rainfall patterns. Achieve coordinated emission reduction of water nitrogen and gaseous nitrogen through a dynamic weight allocation mechanism. The source reduction, process control, and end-of-pipe treatment stages are as follows: The source reduction process focuses on reducing nitrogen input and optimizing nitrogen forms. Through nitrogen reduction regulation, biochar application, and deep fertilization, the total amount of nitrogen entering the environment is controlled at the source. The process control link focuses on intercepting and retaining lost nitrogen. Through the coupled configuration of ecological ridge cultivation, plant hedges and straw mulch, multiple control barriers are set up during nitrogen migration. The end-of-pipe treatment process focuses on nitrogen purification and reuse, using a pond-constructed wetland system to collect and treat slope runoff, thereby achieving the final purification and resource utilization of nitrogen.

[0024] The three links are interconnected and work synergistically. Source reduction alleviates the pressure on process control and end-of-pipe treatment; process control intercepts nitrogen that is not controlled by source reduction; end-of-pipe treatment treats nitrogen that is not intercepted by source reduction and process control; through system optimization of the whole chain, comprehensive reduction of nitrogen loss is achieved.

[0025] In some embodiments, nitrogen reduction regulation, biochar application, and deep fertilization are specifically employed as follows: (1) Nitrogen reduction and regulation: Based on the soil nutrient test results and crop fertilizer requirements, the conventional nitrogen application rate will be reduced by 30% to 50%, the mass ratio of base fertilizer to topdressing will be adjusted to 3:2, and topdressing will be applied by hole application and covered with soil instead of traditional broadcasting to avoid the rapid loss of fertilizer by runoff and seepage after topdressing during the rainy season; if the forecast rainfall exceeds 30 mm within 7 days after fertilization, fertilization will be postponed to 2 to 3 days after the rainfall. (2) Biochar application: Directional regulation and chemical cross-linking of hydroxyl groups on the biochar surface, including: ① Directional regulation of hydroxyl content on biochar surface: The density of hydroxyl (-OH) on biochar surface has a quantitative regulatory effect on the crosslinking structure and slow-release performance of polyurethane coating: an appropriate amount of hydroxyl content (about 0.82 mmol / g) can significantly enhance the crosslinking density and anti-swelling properties of the coating, thus prolonging the fertilizer release cycle, while excessive hydroxyl content (1.96 mmol / g) will increase the hydrophilicity and brittleness of the coating, thereby reducing the slow-release performance.

[0026] Based on this, this embodiment performs targeted control of hydroxyl content in the biochar preparation process: Raw material selection: Use crop straw (peanut straw, rapeseed straw or corn straw), which is washed, crushed and sieved (60 mesh) before use; Pyrolysis process control: Pyrolysis is performed at 400-500℃ with limited oxygen, a heating rate of 10℃ / min, and a holding time of 2-4 hours. The surface hydroxyl content is controlled by adjusting the holding time: after 2 hours of holding, the hydroxyl content is approximately 0.82 mmol / g (suitable), and after 4 hours, the hydroxyl content can reach 1.96 mmol / g (excessive). Therefore, the pyrolysis process in this embodiment is as follows: oxygen-limited pyrolysis at 500℃, heating rate of 10℃ / min, and holding time of 2 hours. ② Chemical crosslinking modification of biochar and polyurethane: The hydroxyl groups (-OH) on the surface of biochar react with the isocyanate groups (-NCO) in the polyurethane prepolymer to form new urethane bonds (-COONH-), constructing a three-dimensional crosslinking network, and completing the modification and application simultaneously. This chemical crosslinking structure enables the modified material to have both the adsorption function of biochar and the slow-release function of polyurethane, rather than a simple physical mixture. Modification process: Hydroxyl-directed biochar (particle size 2-5mm) is mixed with hydrophilic polyurethane material (W-OH) at a mass ratio of 1:0.1-0.8 and mixed in a mixer for 10-15 minutes to form a premix. After the premix is ​​applied to the soil, the -OH groups on the surface of the biochar and the -NCO groups of the polyurethane come into full contact and undergo a cross-linking reaction to form a stable carbon-nitrogen covalent bond structure. Application after modification: Apply the premix 5-7 days before sowing (of which, the amount of hydroxyl-directed biochar is 10-20 t / hm). 2 (Upper limit is taken when pH < 5.0, middle value is taken when pH = 5.0~5.5, and lower limit is taken when pH > 5.5). The premix and base fertilizer (accounting for 60% of the total nitrogen application) are simultaneously spread on the ridge surface, then plowed or furrowed and covered with soil to ensure that the premix is ​​evenly mixed with the top 15~20cm of soil. The cross-linking reaction is completed naturally in the soil, and a stable carbon-nitrogen covalent bond structure is formed after 24~48 hours. ③ Layered regulation: Biochar and polyurethane with hydroxyl-directed regulation were applied to different depths of the soil profile in different proportions, as shown in Table 1, forming a functional gradient of inhibition-adsorption-slow release, which correspond to the control requirements of different nitrogen loss pathways. Table 1. Application amounts of biochar and polyurethane at different depths after hydroxyl-directed regulation.

[0027] ④ Application timing: Surface barrier layer: After sowing and before emergence, the premix is ​​applied to the ridge surface and used in conjunction with straw mulching; Rhizosphere adsorption layer: When applying base fertilizer, the premix is ​​applied simultaneously to a depth of 10-15cm; Deep permeability barrier layer: When preparing the land and ridging, the premix is ​​applied to a depth of 15-25cm and completed before autumn sowing. Among them, the heavy clay soil causes deep seepage to be dominated by preferential flow. The deep barrier layer utilizes the hydrophobicity and three-dimensional network structure of modified biochar to effectively fill large pores and block preferential flow channels. The high proportion of polyurethane on the surface can form a flexible membrane structure to reduce raindrop splash erosion. (4) Modified biochar achieves synergistic emission reduction of water nitrogen and gaseous nitrogen through the following pathways, including: Physical adsorption: The well-developed porous structure adsorbs nitrate nitrogen, reducing deep leaching; Chemical cross-linking slow release: The biochar-polyurethane cross-linking network slows down the fertilizer release rate, reduces the instantaneous peak concentration of nitrogen in the soil solution, and reduces the risk of runoff scouring and leaching; Bioregulation: Inhibits the activity of nitrifying bacteria and reduces N2O emissions; pH buffering: Alleviates soil pH fluctuations after fertilization and reduces NH3 volatilization.

[0028] In some embodiments, a coupled configuration of ecological ridge cultivation, plant hedges, and straw mulch is used to establish multiple barriers to nitrogen migration, specifically: (1) Ecological ridge cultivation: Construct a ridge and furrow system along the contour lines on the slope, with a ridge width of 60-80cm, a ridge height of 10-20cm, and a furrow depth of 10-15cm; Ecological ridge cultivation can alter micro-topography, slow down slope runoff velocity, increase precipitation infiltration time, and reduce surface runoff and scouring force; crops planted on the ridges can accumulate a small amount of runoff in the furrows, enabling on-site interception and utilization of rainwater. (2) Plant hedges: Perennial daylily plant hedges are laid along the contour lines in the sloping farmland, with a width of 60cm. The spacing between hedges is dynamically adjusted according to the slope: 10m when the slope is <10°, and 8m when the slope is 10°~20°. The above-ground part of the plant hedge forms a biological ridge, which blocks surface runoff and reduces runoff velocity; the underground part has roots to stabilize the soil and protect the slope. Through the dual mechanisms of physical interception and biological absorption, it reduces the amount of nitrogen lost with surface runoff and sediment. The daylily plant hedge has both ecological interception function and economic benefits. Its flower stems can be sold fresh as vegetables or processed. After the leaves wither, they can be cut and used as green manure or silage, realizing short-term benefits for long-term benefits. However, the flower stem harvesting period (June-July) coincides with the concentrated rainfall period in the red soil region of southern China, resulting in a periodic conflict between harvesting intensity and interception function. To resolve this contradiction, this embodiment proposes a coupled management scheme for harvesting and interception functions: ① Stubble height control: When harvesting flower stems, retain 10-15cm of stem at the base to preserve some of the photosynthetic capacity of the stems and leaves in order to maintain the continuous growth and basic interception function of the plant hedge; ② Harvesting intensity constraints: Each harvest should not exceed 70% of the total number of flower stalks, and 30% of the flower stalks should be retained to continue growing and producing seeds, so as to maintain the interception effect of the plant hedge and ensure the natural regeneration of the population. ③ Returning leaves to the field as resources: After the flower stems are harvested, the withered and yellow leaves are cut off and evenly covered on the ridge surface to serve as organic material to be returned to the field, which has the dual effect of conserving moisture and enriching the soil. By implementing a three-pronged management approach of stubble retention, controlled harvesting, and returning the crop to the field, the daylily hedges can maintain a stable slope interception function while being harvested and utilized, thus achieving a synergistic and sustainable balance between ecological and economic benefits. (3) Straw mulching: In the peanut-rapeseed rotation system, straw (rice straw) is evenly covered after peanut sowing, with a coverage of 3000~4500 kg / hm² and a coverage thickness of 3~5 cm. After rapeseed is harvested, the straw is crushed and returned to the field. Straw mulching reduces the loss of water nitrogen carried by surface runoff sediment by reducing the kinetic energy of raindrop erosion and reducing slope scouring. At the same time, it reduces the frequency of soil wetting and drying by conserving water and moisture, and inhibits the drastic fluctuations in the nitrification-denitrification process, thereby reducing N2O emissions. In summary, ecological ridge cultivation, plant hedges, and straw mulch are spatially complementary: ecological ridge cultivation alters the micro-topography, increases infiltration, and reduces runoff; plant hedges intercept runoff and sediment along the transverse slope; straw mulch protects the ridge surface soil from rain splash; the coupling of these three elements can achieve full-chain control of surface-soil-deep infiltration, effectively intercepting nitrogen loss through various pathways.

[0029] In some embodiments, the process control steps also include simplified no-till combined with inter-row cultivation and hilling, specifically: In peanut-rapeseed rotation, after the rapeseed crop is harvested, the soil is not turned over. Peanuts are sown in holes along the original contour ridges, with two rows per ridge. The ridges are 64 cm wide, 10 cm high, and the furrows are 20 cm wide and 15 cm deep. The row spacing is 32 cm and the hole spacing is 15 cm. The sowing depth is 4-5 cm. During the flowering and pegging stage of peanuts, the soil is cultivated and hilled up to increase the ridge height to 13-15 cm. Before rapeseed sowing or during the winter fallow and wet period, the ridge surface is cultivated to a depth of 15-20 cm to improve the compaction of the red soil. Deep cultivation is not performed during periods of low rainfall and drought. Simplified no-till farming maintains the stability of the topsoil environment by reducing soil disturbance, reduces the full contact between fertilizer and soil urease, reduces the loss of gaseous nitrogen by reducing nitrification-denitrification substrate NH3, and at the same time reduces the deep leaching of nitrogen and its migration with soil erosion caused by loose soil.

[0030] In some embodiments, the pit-constructed wetland system specifically refers to: In the catchment area at the foot of the slope, pits or ponds are utilized or constructed according to local conditions. Artificial wetlands are built downstream of the outlet of the pits or ponds. The hydraulic retention time of the artificial wetlands is 3-5 days. Aquatic plants (myriophyllum, calamus, or canna) are planted. The wetland substrate uses a gravel-biochar composite filler, with the biochar mixing ratio being 10%-15% of the filler volume. Constructed wetlands remove nitrogen from water bodies through plant absorption, substrate adsorption, and microbial nitrification-denitrification, achieving a total nitrogen removal rate of 60% to 90%.

[0031] In some embodiments, dynamic regulation is implemented based on the quantified contribution rate of nitrogen loss pathways and annual rainfall patterns, and coordinated emission reduction of water nitrogen and gaseous nitrogen is achieved through a weighted dynamic allocation mechanism, including: Establish a precise spatiotemporal regulation strategy for coordinated reduction of water-nitrogen and gaseous nitrogen emissions. Implement dynamic regulation based on annual rainfall patterns, planting season, and growth period. Achieve precise targeted control of nitrogen loss pathways through a dynamic weight allocation mechanism. Specifically: (1) Weighted dynamic allocation mechanism based on annual rainfall patterns: using the percentage anomaly of the baseline precipitation value in the 30 years prior to peanut planting, P a Classification of year types: P a ≥20% is considered a wet year, P a A year with a water level ≤-20% is considered a dry year. <P a <20% is considered a normal water year. Based on the measured range of apparent nitrogen loss rate in water under different year types (4.38%~22.17%), a dynamic allocation model for coordinated emission reduction weights of water nitrogen and gas nitrogen was established (see Table 2), and the emission reduction input ratio of the two types of losses was dynamically adjusted.

[0032] Table 2 Dynamic Allocation Model of Water-Nitrogen and Gas-Nitrogen Coordinated Emission Reduction Weights

[0033] In years with abundant rainfall, the risks of runoff and deep seepage increase significantly. Water control and nitrogen fixation measures such as ecological ridge cultivation, vegetation hedges, and deep application of biochar (15-20 t / hm²) should be prioritized according to weighting ratios, while the intensity of investment in gaseous nitrogen emission reduction measures should be appropriately reduced. In years with dry rainfall, the proportion of ammonia volatilization and N2O emissions increases under drought conditions. Ammonia suppression measures such as deep fertilization (base fertilizer depth >10 cm, topdressing >8 cm) and soil covering and compaction should be prioritized, while the intensity of investment in water and nitrogen emission reduction measures should be appropriately reduced. In years with normal rainfall, all measures should be allocated with equal weighting.

[0034] (2) Precise regulation strategy based on growth period: Differentiated input is implemented according to the nitrogen loss characteristics of different growth periods, and the resource allocation ratio is secondary allocated with reference to the current year's weight: Basal fertilizer period (5-7 days before sowing): Nitrogen gaseous emissions account for 33.33%-47.22% of the total growth period (up to the upper limit in dry years). At this stage, the focus is on controlling seepage and leakage. The fertilizer is applied to the side of the seed hole 5-10 cm below the side to reduce the direct contact between the fertilizer and the surface free water. At the same time, biochar is applied to adsorb the surplus nitrogen. Topdressing period (seedling stage to flowering stage): The focus is on controlling erosion and diameter. The application method is hole application or furrow application, combined with straw mulching (mulching amount 4-6 t / hm). 2 Enhance the soil's resistance to erosion and reduce fertilizer migration with surface runoff; during the post-harvest fallow period: focus on residual nitrogen management, reduce the direct erosion of the topsoil by non-growing season rainfall by planting green manure (such as milkvetch) or straw mulching, and prevent residual nitrogen loss through runoff or seepage.

[0035] (3) Precise configuration strategy based on the contribution rate of nitrogen loss pathways: Through years of location monitoring, the contribution rate distribution of each nitrogen loss pathway in peanut season in red soil dry slope is clarified (based on quantifiable active nitrogen loss, the total loss rate is 5.57%~14.21%). Based on this, a gradient configuration scheme of technical measures is established, as shown in Table 3.

[0036] Table 3 Gradient Configuration Scheme

[0037] Deep seepage contributes the most, so deep application of biochar (15~20 t / hm) should be prioritized. 2 The primary emission reduction measures include reducing nitrogen leaching at the source, such as biochar adsorption and nitrification inhibitors. N2O emissions contribute the second largest share, which can be controlled through biochar adsorption and synergistic control of nitrification inhibitors. Surface runoff contributes 20%–30%, and engineering measures such as ecological ridge cultivation and vegetation hedges are prioritized to intercept runoff. NH3 volatilization contributes 10%–15%, which can be effectively controlled through deep fertilization and soil covering and compaction. Resources are allocated to each emission reduction measure according to its weight for the current year to maximize overall emission reduction efficiency.

[0038] In summary, this embodiment employs a three-tiered progressive decision-making chain—namely, weighting of annual rainfall patterns, decomposition of fertility periods, and targeted configuration of loss pathways—to ensure that the technology configuration not only meets the macro-level requirements at the annual scale but also precisely aligns with the nitrogen loss characteristics of each fertility period and pathway, thereby achieving systematic and coordinated emission reduction of water and gaseous nitrogen losses.

[0039] Example 1: Nitrogen Reduction and Fertilization Regulation The nitrogen reduction and regulation fertilization and tillage schemes are shown in Table 4.

[0040] Table 4. Nitrogen Reduction and Fertilization Regulation Scheme

[0041] Surface runoff and TN concentrations in peanut fields under different nitrogen application levels, such as Figure 1 As shown, the nitrogen output flux of peanut fields under different nitrogen application levels with respect to surface runoff and infiltration is as follows: Figure 2 As shown.

[0042] The results show that: N 100% The treated TN runoff loss was 9.43 kg·hm. -2 N 1 / 2 The treatment resulted in the lowest TN runoff loss (7.15 kg / hm). 2 The N0 treatment resulted in the largest TN runoff loss (12.26 kg / hm). 2 N 100% and N 1 / 2 The treatments resulted in smaller TN runoff losses, which may be related to the high biomass and vigorous growth of peanut plants in both treatments, which effectively intercepted nitrogen and other nutrients carried by the runoff.

[0043] Example 2: Layered application of modified biochar-polyurethane The experiment was conducted in a peanut-rapeseed rotation soil trough with a slope of 8° and equipped with lateral interflow and deep infiltration water collection functions. All treatments were uniformly applied with pure nitrogen at 150 kg / hm² (a reduction of about 17% compared to the conventional method), and phosphorus and potassium fertilizers were applied according to the local conventional application rate. A total of 6 treatments were set up. The biochar application experiment design is shown in Table 5.

[0044] Table 5. Experimental Design for Biochar Application

[0045] The results showed that compared with the control (CK), the T2 treatment reduced total nitrogen loss by 26.8%, including a 22.3% reduction in surface runoff nitrogen (TN) and a reduction in deep infiltration nitrogen (NO3). - -N emissions were reduced by 29.7% and N2O emissions by 14.6%, significantly better than single treatments of BC20 (15.2%) and W-OH (12.7%).

[0046] The total nitrogen emission reduction rate of T2 increased by 8.9% compared to T1, indicating that after optimizing the application from a single rhizosphere layer to a three-layer spatial configuration of surface-root-deep, the synergistic inhibition effect of the material on nitrogen loss through different migration pathways was significantly enhanced.

[0047] T3 showed a 7.3% increase in total nitrogen emission reduction compared to T2, confirming that by optimizing the hydroxyl content of biochar to 0.82 mmol / g through a 500℃ pyrolysis and 2-hour holding process based on stratified application, the material's resistance to NH4+ can be further enhanced. + The adsorption and fixation of urea and the slow-release regulation of urea hydrolysis.

[0048] Example 3: Coupling of Rainfall Year-Type Weighting, Precise Regulation of Growth Period, and Nitrogen Loss Pathway Contribution Rate-Oriented Configuration Three treatment groups were set up on a typical red soil dry slope (slope of 12°, peanut-rapeseed rotation system), and three consecutive hydrological years were observed (including one wet year, one normal year, and one dry year). Each group was repeated three times. The specific experimental design is shown in Table 6.

[0049] Table 6 Configuration of Different Control Modes

[0050] The results showed that: (1) Comprehensive emission reduction effect: During the three-year observation period, the total nitrogen loss (the sum of water nitrogen and gas nitrogen) in the T2 treatment was reduced by 34.6% compared with the CK, of which water nitrogen loss was reduced by 37.2% and gas nitrogen emission was reduced by 31.8%. The total nitrogen emission reduction rate of T2 was 10.3 percentage points higher than that of T1, indicating that the three-layer coupled regulation mechanism can break through the emission reduction bottleneck of single measures or fixed parameter systems and effectively alleviate the antagonistic effect between water nitrogen and gas nitrogen emission reduction.

[0051] (2) Annual Adaptive Capability: In wet years, the T2 treatment achieved a water nitrogen reduction rate of 40.5% and a gas nitrogen reduction rate of 27.3%; in dry years, the gas nitrogen reduction rate reached 36.4% and the water nitrogen reduction rate was 28.1%; in normal years, the reduction rates of both types of losses remained stable in the range of 32% to 35%. The above results indicate that by dynamically allocating the annual precipitation weights, the technical configuration can be adaptively adjusted according to precipitation characteristics, achieving targeted control with an emphasis on water nitrogen control in wet years and an emphasis on gas nitrogen control in dry years.

[0052] (3) Effects of precise control during the growing season: After deep application of fertilizer during the basal fertilizer period, ammonia volatilization during the basal fertilizer period in dry years was reduced by 30.8% compared with the control (CK); during the topdressing period, combined with hole application and straw mulching, the TN loss from surface runoff was reduced by 32.2% compared with the control (CK); during the fallow period, planting green manure reduced the loss of residual nitrogen in the soil during the non-growing season by 30.5% compared with the control (CK). The above data verified the blocking effect of differentiated regulation during the growing season on each key loss node.

[0053] (4) Configuration effectiveness guided by contribution rate of loss pathways: After prioritizing the prevention and control of deep seepage (first priority) and gaseous loss (second priority), T2 treatment of deep seepage NO3 - -N emissions were reduced by 35.9%, and N2O emissions were reduced by 29.4%. Combined with the third and fourth priority measures, surface runoff TN was reduced by 32.2%, and ammonia volatilization was reduced by 33.7%. These results indicate that configuring technical measures according to the contribution rate gradient of loss pathways can precisely target limited resources to major loss pathways, maximizing overall emission reduction efficiency.

[0054] (5) Stable yield and increased efficiency: The average yield of peanuts and rapeseed in the T2 treatment increased by 3.8% and 2.9% respectively compared with the CK, and the nitrogen fertilizer partial productivity increased by 16.7%. This shows that the fully coupled dynamic regulation can achieve synergistic nitrogen emission reduction while taking into account crop yield formation, and has production applicability.

[0055] This embodiment verifies the effectiveness of a three-layer coupled regulation method: weighted allocation of rainfall annual patterns, precise regulation of the growth period, and nitrogen loss pathway contribution rate-guided configuration. This method transforms macro-level rainfall annual patterns into operable parameter adjustment criteria through weight assignment, achieves precise temporal control of key fertilization nodes through growth period segmentation, and realizes spatial optimization of technical resources through contribution rate analysis. These three elements are coupled and progressively layered, forming a spatiotemporally coordinated precise regulation strategy suitable for the systematic and synergistic reduction of water and gaseous nitrogen losses in red soil dry slopes.

[0056] Example 4: Combining a three-stage coordinated emission reduction system of source reduction, process control, and end-of-pipe treatment with a dynamic regulation mechanism Two treatment groups were set up on a typical red soil dry slope (slope of 15°, peanut-rapeseed rotation), and the observation was carried out continuously for 3 years. Each group was repeated 3 times. The specific technical model is shown in Table 7.

[0057] Table 7 Configuration Schemes for Different Technology Modes

[0058] (1) Gradual reduction effect across the entire chain: At the source reduction stage, nitrogen reduction and modified biochar were applied in layers, reducing the nitrogen input load of the system by about 30%; in the process control stage, the synergistic effect of ecological ridge cultivation, plant hedges and straw mulch achieved an interception rate of 52.3% for residual nitrogen loss during migration; in the end-of-pipe treatment stage, the slope foot pond-artificial wetland system achieved a removal rate of 48%~68% for total nitrogen in slope runoff. The three-stage system was connected step by step and reduced in a step-by-step manner. The average total nitrogen loss of FT treatment over three years was reduced by 38.7% compared with CK, indicating that the whole-chain integrated mode has a significant synergistic effect compared with conventional farming.

[0059] (2) Synergistic Reduction Effect of Water and Gas Nitrogen: The FT model, combined with a dynamic weight allocation mechanism, adaptively adjusts the control focus according to the rainfall year type. In wet years, the water nitrogen reduction weight is set to 0.65, focusing on the control of deep seepage pathways, and water nitrogen loss is reduced by 42.6% compared with the control (CK). In dry years, the gas nitrogen reduction weight is set to 0.65, focusing on the control of ammonia volatilization and N2O emissions, and gas nitrogen emissions are reduced by 39.2% compared with the control (CK). The above results show that the whole-chain model can achieve synergistic reduction of water and gas nitrogen losses under different rainfall year types, effectively alleviating the antagonistic effect of the two types of losses increasing at the expense of each other under single measures.

[0060] (3) Effect of nitrogen loss control during non-growing season: Planting purple clover green manure during the fallow period and combining it with straw mulching measures, the residual nitrogen loss in the soil during the non-growing season of the FT treatment was reduced by 35.8% compared with the CK, indicating that the whole-chain model can effectively reduce the intensity of nitrogen loss during the non-growing season in dry red soil slopes in the south, filling the gap in seasonal control.

[0061] (4) Effects on stable yield and nitrogen resource utilization: The average yields of peanuts and rapeseed treated by FT were +2.3% and +1.7% respectively compared with CK, and the difference was not statistically significant (P>0.05), indicating that the emission reduction measures did not have a negative impact on crop yield formation. The total nitrogen concentration of the runoff water collected and treated by the slope foot pond-artificial wetland system was reduced to below 15 mg / L, which can be used as a supplementary irrigation water source during the dry season to realize the cascade utilization of nitrogen resources.

[0062] This embodiment verifies the synergistic effect of coupling the three-stage system of source reduction, process control, and end-of-pipe treatment with a dynamic regulation mechanism. Source reduction lowers the nitrogen input load, process control intercepts reactive nitrogen along the migration path, and end-of-pipe treatment ultimately eliminates residual nitrogen. These three stages are progressive and mutually supportive. On this basis, a dynamic weight adjustment mechanism based on rainfall annual patterns is superimposed, enabling the technology configuration to be adaptively optimized according to precipitation characteristics. This achieves full-time, full-pathway systematic management of nitrogen loss in red soil dry slopes, providing a replicable technical paradigm for the prevention and control of agricultural non-point source pollution in southern dry slopes.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tillage method for coordinated reduction of nitrogen loss on dry red soil slopes, characterized in that, include: Establish a three-stage coordinated emission reduction system consisting of source reduction, process control, and end-of-pipe treatment. Implement dynamic regulation based on the quantitative contribution rate of nitrogen loss pathways and annual rainfall patterns. Achieve coordinated emission reduction of water nitrogen and gaseous nitrogen through a dynamic weight allocation mechanism. The source reduction, process control, and end-of-pipe treatment stages are as follows: The source reduction process focuses on reducing nitrogen input and optimizing nitrogen forms. Through nitrogen reduction regulation, biochar application, and deep fertilization, the total amount of nitrogen entering the environment is controlled at the source. The process control link focuses on intercepting and retaining lost nitrogen. Through the coupled configuration of ecological ridge cultivation, plant hedges and straw mulch, multiple control barriers are set up during nitrogen migration. The end-of-pipe treatment process focuses on nitrogen purification and reuse, using a pond-constructed wetland system to collect and treat slope runoff, thereby achieving the final purification and resource utilization of nitrogen.

2. The tillage method for coordinated reduction of nitrogen loss on dry red soil slopes as described in claim 1, characterized in that, In nitrogen reduction regulation, the mass ratio of base fertilizer to topdressing is 3:2, and topdressing is applied by hole application and covering with soil.

3. The tillage method for coordinated reduction of nitrogen loss on red soil dry slopes as described in claim 1, characterized in that, In the application of biochar, the hydroxyl groups on the surface of the biochar are directionally regulated and chemically cross-linked, including: the biochar is pyrolyzed under limited oxygen at 500℃ with a heating rate of 10℃ / min and a holding time of 2 hours to obtain biochar with hydroxyl groups directionally regulated; the biochar with hydroxyl groups directionally regulated is mixed with polyurethane at a mass ratio of 1:0.1-0.8 and mixed for 10-15 minutes to form a premix, which is then applied to the soil.

4. A tillage method for coordinated reduction of nitrogen loss on dry red soil slopes as described in claim 3, characterized in that, In the surface barrier layer, after sowing and before emergence, the premix is ​​applied to the ridge surface in conjunction with straw mulch, with a biochar:polyurethane mass ratio of 1:0.1~0.2; in the rhizosphere adsorption layer, the premix is ​​applied simultaneously with the basal fertilizer, at a depth of 10~15cm, with a biochar:polyurethane mass ratio of 1:0.2~0.3; in the deep permeability barrier layer, the premix is ​​applied during land preparation and ridging, at a depth of 15~25cm, with a biochar:polyurethane mass ratio of 1:0.5~0.

8.

5. A tillage method for coordinated reduction of nitrogen loss on dry red soil slopes as described in claim 1, characterized in that, By coupling ecological ridge cultivation, plant hedges, and straw mulch, multiple barriers are established during nitrogen migration, specifically: Ecological ridge cultivation: Construct a ridge and furrow system along the contour lines on the slope, with a ridge width of 60-80cm, a ridge height of 10-20cm, and a furrow depth of 10-15cm; Plant hedges: Perennial daylily hedges are laid along contour lines in sloping farmland, with a width of 60cm. The spacing between hedges is dynamically adjusted according to the slope: 10m when the slope is <10° and 8m when the slope is 10°~20°. Straw mulching: The amount of straw mulching is 3000~4500 kg / hm², and the mulching thickness is 3~5 cm.

6. A tillage method for coordinated reduction of nitrogen loss on dry red soil slopes as described in claim 1, characterized in that, Red soil dry slopes are planted with peanut-rapeseed rotation or corn-legume intercropping.

7. A tillage method for coordinated reduction of nitrogen loss on dry red soil slopes as described in claim 6, characterized in that, Process control measures also include simplified no-till farming combined with inter-row cultivation and hilling, specifically: In peanut-rapeseed rotation, after the rapeseed crop is harvested, the soil is not turned over. Peanuts are sown in holes along the original contour ridges, with two rows per ridge. The ridges are 64 cm wide, 10 cm high, and the furrows are 20 cm wide and 15 cm deep. The row spacing is 32 cm and the hole spacing is 15 cm. The sowing depth is 4-5 cm. During the flowering and pegging stage of peanuts, the soil is cultivated and hilled up to increase the ridge height to 13-15 cm. Before rapeseed sowing or during the winter fallow and wet period, the ridge surface is cultivated to a depth of 15-20 cm to improve the compaction of the red soil. Deep cultivation is not carried out during periods of little rain and drought.

8. A tillage method for coordinated reduction of nitrogen loss on red soil dry slopes as described in claim 1, characterized in that, The pond-constructed wetland system is specifically as follows: In the catchment area at the foot of the slope, pits and ponds are utilized or constructed according to local conditions. Artificial wetlands are built downstream of the outlet of the pits and ponds. The hydraulic retention time of the artificial wetlands is 3 to 5 days. Aquatic plants are planted. The wetland substrate uses a combination of gravel and biochar, with the biochar mixing ratio being 10% to 15% of the filler volume.

9. A tillage method for coordinated reduction of nitrogen loss on dry red soil slopes as described in claim 1, characterized in that, Dynamic regulation is implemented based on annual rainfall patterns, and a targeted prevention and control strategy for coordinated reduction of water nitrogen and gaseous nitrogen emissions is established. This is achieved through a dynamic weight allocation mechanism to coordinate the reduction of water nitrogen and gaseous nitrogen losses. Specifically, the following steps are included: (1) The percentage anomaly P of the baseline precipitation value 30 years before peanut planting a Classification of year types: P a ≥20% is considered a wet year, P a A year with a water level ≤-20% is considered a dry year. <P a <20% is considered a normal water year; (2) Based on the measured range of apparent nitrogen loss rate in different water types (4.38%~22.17%), the basic weight W for nitrogen emission reduction in high-water years was set. w =0.65, average annual W w =0.50 and dry year W w =0.35, corresponding to the basic weight W for nitrogen emission reduction. a =1-W w .

10. A tillage method for coordinated reduction of nitrogen loss on dry red soil slopes as described in claim 9, characterized in that, Differentiated regulation is implemented based on the nitrogen loss characteristics at different growth stages. Specifically: during the basal fertilizer stage, the focus is on reducing seepage and leakage by deep application of base fertilizer to reduce the direct contact area between fertilizer and surface water; during the topdressing stage, the focus is on reducing runoff and preventing erosion by using hole or trench application methods to reduce the risk of fertilizer loss with surface runoff, while straw mulching is used to enhance surface protection; during the fallow period after harvest, the focus is on residual nitrogen management by planting green manure or mulching measures to reduce direct erosion of the topsoil by rainfall and prevent residual nitrogen from being lost with runoff and seepage during the non-growing season.

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