A method for the application of biochar in arid zone agriculture

Abstract

The application belongs to the technical field of biochar application, and provides a biochar arid region agricultural application method, which comprises application of biochar to total nitrogen content of soil in monoculture and intercropping planting modes; the application utilizes physical characteristics such as water retention of biochar to improve soil nutrient availability and crop nutrient utilization efficiency; biochar in different planting modes significantly reduces total nitrogen content of soil in a 60-160cm soil layer, and the better the adsorption effect of biochar on total nitrogen content of soil, the more conducive to nitrogen requirement of crops in the growth and development process; intercropping planting mode significantly improves nitrate nitrogen content of soil in a 0-160cm soil layer, and addition of biochar can obviously reduce leaching risk of nitrate nitrogen, can reduce leaching loss amount of water-soluble ions such as nitrate nitrogen, and delay migration and conversion time; monoculture planting mode significantly improves ammonium nitrogen content of soil in a 0-160cm soil layer, and addition of biochar can obviously reduce loss risk of ammonium nitrogen, and is conducive to growth and development of crops.

Description

Technical Field

[0001] This invention belongs to the field of biochar application technology, specifically a method for applying biochar in arid-region agriculture. Background Technology

[0002] The arid Northwest region suffers from drought, poor soil structure, low water and fertilizer retention capacity, and a fragile ecosystem, resulting in low overall agricultural productivity. Therefore, the sustainable development of agriculture in arid regions is of great significance to ensuring my country's food security.

[0003] Biochar is a carbonaceous solid material prepared from biomass through high-temperature pyrolysis or slow combustion under low-oxygen conditions. It can improve the physical structure of soil, increase soil porosity, and promote crop root growth and soil microbial activity. Due to its large specific surface area and porous nature, biochar can adsorb and retain nutrients in the soil, reduce water and nutrient loss, and thus improve soil fertility. Because its surface functional groups can adsorb heavy metals and other pollutants in the soil, it helps reduce the impact of these harmful substances on the environment and plants, promotes the cycling and transformation of nutrients in the soil, and improves nutrient utilization efficiency.

[0004] Soil total nitrogen content refers to the total content of nitrogen in all forms in the soil, including organic and inorganic nitrogen. Organic nitrogen accounts for approximately 95% of total soil nitrogen and includes humus, proteins, and amino acids, while inorganic nitrogen mainly includes ammonium nitrogen and nitrate nitrogen, which can be directly absorbed by plants. Soil total nitrogen content is one of the important indicators for evaluating soil fertility and nutrient status, and it is of great significance for agricultural production and soil nutrient management.

[0005] To this end, a biochar application method for arid zone agriculture was proposed to understand the effects of biochar application under different patterns on the content of total nitrogen, nitrate nitrogen and ammonium nitrogen in the soil. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for applying biochar in arid-region agriculture, thereby resolving the issues raised in the background section.

[0007] A method for applying biochar in arid agricultural areas, including the application of biochar to the total nitrogen content of soil under monoculture and intercropping modes.

[0008] Specifically, intercropping flax and peas under different planting patterns significantly increased the total nitrogen content in the shallow soil layer (0-60 cm). Compared with the treatment without biochar, the addition of 10 t·hm² significantly increased the total nitrogen content. -2 Under biochar treatment, biochar significantly reduced the total nitrogen content in the soil layer of 60-160cm, and the better the adsorption effect of biochar on total nitrogen content in the soil, the better it is for the nitrogen requirements of crops during growth and development.

[0009] Preferably, the application of biochar in intercropping planting patterns affects the application of nitrate nitrogen in the soil.

[0010] Specifically, intercropping significantly increased the nitrate nitrogen content in the 0-160cm soil layer compared to monoculture, and added 10 t·hm² of nitrogen. -2 Biochar treatment significantly increased the accumulation of soil nitrate nitrogen in flax and pea plants, with the addition of 10 t·hm² of biochar significantly increasing the amount of nitrate nitrogen. -2 Biochar treatment can increase the nitrate nitrogen content in the 0-20cm soil layer and has good adsorption capacity. Adding 20t·hm² of biochar further increases the nitrate nitrogen content. -2 Biochar treatment can significantly increase the nitrate nitrogen content in soil at a depth of 100-160 cm, indicating that biochar has the best adsorption effect on ammonium nitrogen in the soil, can significantly reduce the risk of ammonium nitrogen leaching, and can reduce the leaching loss of water-soluble ions such as nitrate nitrogen and delay the migration and transformation time.

[0011] Preferably, the application of biochar in monoculture planting patterns affects the application of ammonium nitrogen in the soil.

[0012] Specifically, monoculture significantly increased the ammonium nitrogen content in the 0-160cm soil layer compared to intercropping, with an additional 10 t·hm² of ammonium nitrogen. -2 Biochar treatment significantly increased the accumulation of soil ammonium nitrogen in flax and pea plants, and improved the soil ammonium nitrogen content in the 0-20 cm soil layer, while also exhibiting good adsorption capacity. Adding 20 t·hm² of biochar further increased the soil ammonium nitrogen content. -2 Biochar treatment significantly increased the ammonium nitrogen content in soil at a depth of 120-160 cm, indicating that different planting patterns and biochar application rates have different effects on the retention effect of ammonium nitrogen in the soil. Adding biochar has the best adsorption effect on ammonium nitrogen in the soil, which can significantly reduce the risk of ammonium nitrogen leaching and is beneficial to crop growth and development.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. This invention addresses the challenges of low rainfall and high evaporation in dryland areas by utilizing the water-retention and other physical properties of biochar to improve soil nutrient availability and crop nutrient utilization efficiency. Intercropping significantly increases the total nitrogen content in the 0-60cm soil layer. Simultaneously, the B10 biochar treatment significantly reduces the total nitrogen content in the 60-160cm soil layer compared to the B0 treatment, indicating that the better the adsorption effect of biochar on total nitrogen in shallow soil, the better it meets the nitrogen requirements of crops during their growth and development.

[0015] 2. Intercropping can significantly increase the nitrate nitrogen content in the 0-160cm soil layer. The application of biochar has the best adsorption effect on nitrate nitrogen in the soil, which can significantly reduce the risk of nitrate nitrogen loss, reduce the leaching loss of water-soluble ions such as nitrate nitrogen, and delay the migration and transformation time.

[0016] 3. Monoculture can significantly increase the ammonium nitrogen content in the 0-160cm soil layer. Adding biochar has the best adsorption effect on ammonium nitrogen in the soil, which can significantly reduce the risk of ammonium nitrogen leaching and is beneficial to crop growth and development. Attached Figure Description

[0017] Figure 1 These are field layout diagrams for different planting patterns according to the present invention;

[0018] Figure 2 This is a distribution characteristic diagram of total nitrogen content in a 0-160cm soil profile of biochar and planting model of the present invention, where A, B, and C represent the pre-sowing, flowering, and harvesting stages of flax and pea, respectively.

[0019] Figure 3 This is a graph showing the time-dynamic changes in soil nitrate nitrogen content caused by the biochar and planting patterns of the present invention.

[0020] Figure 4 This is a graph showing the time-dependent dynamic changes in soil ammonium nitrogen content caused by the biochar and planting patterns of this invention. Detailed Implementation

[0021] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0022] Experimental Design of this Invention: Flax varieties Longya 11 and pea varieties Dingwan 8 were used as experimental materials. A two-factor split-plot design was employed. The main plot represented different planting patterns with three levels: flax monoculture (MF), pea monoculture (MP), and flax intercropped with peas (F||P). The subplot represented different biochar levels with three levels: control (no biochar added) and treatment with 10 t·hm² of biochar added. -2 Biochar treatment (B10), with an addition of 20 t·hm -2 Biochar treatment (B20). A total of 9 treatments were set up, with each treatment replicated 3 times, for a total of 27 plots. See Table 1 for details.

[0023] Table 1 Basic Processes of Experimental Design in this Invention

[0024]

[0025] This invention relates to crop field planting, such as Figure 1As shown. Single-cropping flax: flat planting, sowing density of 7.5 million plants per hectare. -2 Row spacing 20cm, area of ​​the community is 20m² 2 (4.0m × 5.0m); Monoculture peas: flat planting, sowing density 900,000 plants / hm² -2 Planted in rows with a row spacing of 20cm and a plant spacing of 15cm, the plot area is 20m². 2 (4.0m×5.0m); Sesame intercropping with peas: Sesame strips are 80cm wide, planted in 4 rows with a row spacing of 20cm; pea strips are 60cm wide, planted in 3 rows with a row spacing of 20cm and a plant spacing of 15cm. The plot area is 21m². 2 (4.2m×5.0m), with an interleaving bandwidth of 1.4m, and a total of 3 combined bands per cell.

[0026] This invention incorporates straw biochar, derived from corn straw pyrolyzed at 450℃, with a carbon content of 66%, nitrogen content of 1.8%, P2O5 content of 0.7%, K2O content of 1.9%, pH value of 10.8, and CEC of 41.5 cmol / kg, provided by Liaoning Jinhefu Agricultural Development Co., Ltd. All treated biochar was applied once to the surface of the test soil, manually tilled, and then evenly mixed with the 0-20cm soil layer using a rotary tiller. The straw biochar was applied to the soil surface annually and then rotary tilled to a depth of 20cm for two consecutive years. The tested fertilizers were urea (N: 46%), superphosphate (P2O5: 20%), and potassium sulfate (K2O: 52%). N, 150 kg·hm² -2 Based on the local total nitrogen application rate for flax, phosphorus fertilizer, potassium fertilizer, and 2 / 3 of the nitrogen fertilizer were applied as base fertilizer in a single application, while 1 / 3 of the nitrogen fertilizer was applied as top dressing before the flax budding stage. The application rates of phosphorus and potassium fertilizers were 90.0 kg·hm². -2 (P2O5), 52.5 kg·hm -2 (K2O). The planting density for intercropping and monoculture is the same, and other management practices are the same as local routine management.

[0027] The soil sampling method required for this invention is as follows: Soil samples were collected three times in 2021-2022 during the seedling, flowering, and harvesting stages of flax. The sampling depth ranged from 0 to 160 cm, with each 20 cm layer forming a single layer. For monoculture flax, samples were taken between two rows of planting strips. For monoculture peas, samples were taken between two evenly growing plants in the same row. For intercropping, two points were selected simultaneously in the same plot for both flax and peas, and the samples were mixed thoroughly to form a single soil sample. After extracting the corresponding soil sample using a soil auger, the sample was sieved through a 2 mm soil sieve. Then, 50 g of the soil sample was weighed, placed in a resealable bag, and allowed to air dry naturally for storage, for use in determining soil nutrients.

[0028] Soil total nitrogen determination: The determination was performed using an Elemantar elemental analyzer. For each determination, 120 mg of soil sample was weighed, wrapped in aluminum foil using a special tool, and then placed into the elemental analyzer. During the determination, the combustion tube temperature was 1150℃ and the reduction tube temperature was 900℃.

[0029] Determination of soil nitrate nitrogen and ammonium nitrogen: Weigh 5.00 g of dry soil and place it in a 200 mL Erlenmeyer flask. Add 50 mL of 2 mol / L potassium chloride solution, seal the flask tightly, and shake on a shaker for 1 hour. Remove the flask and let it stand until the soil-potassium chloride suspension becomes clear. Filter the suspension with filter paper and take a certain amount of the filtrate. Use a SmartChem450 fully automated discontinuous chemical analyzer (Alliance, France) to determine the soil nitrate nitrogen and ammonium nitrogen.

[0030] Example 1: Application of biochar to total nitrogen content in soil under monoculture and intercropping modes.

[0031] like Figure 1 As shown, biochar and planting patterns have a significant impact on the total nitrogen content in the 0-160cm soil layer, and the total nitrogen content differs significantly at the pre-sowing, flowering, and harvesting stages.

[0032] The highest total nitrogen content in the soil was mainly found in the 0-20 cm soil layer, and under different planting patterns, the B10 treatment with biochar had the highest total nitrogen content. Specifically, the B10 treatment significantly increased total nitrogen content by 4.21% compared to the B0 treatment in pre-sowing monoculture flax, by 12.60% in flowering monoculture pea, and by 17.86% in harvest intercropping flax. Looking at different soil layers, the total nitrogen content in the 0-160 cm soil layer under both MF (monoculture flax) and IF (intercropping flax) conditions generally showed a trend of first increasing, then decreasing, and then increasing again with increasing soil depth. Under different planting patterns, the vertical variation of total nitrogen content in the 0-160 cm soil layer was significantly affected by the biochar level. Under monoculture flax conditions, the total nitrogen content in the 120-160 cm soil layer showed a decreasing trend in all biochar treatments during the flowering period. Under the MF and IF planting patterns, B10 significantly increased soil total nitrogen content by 1.43%–8.78% and 0.71%–4.20% compared to B0 and B20 treatments, respectively. Furthermore, under the IF planting pattern, B0, B10, and B20 significantly increased by 18.01%–28.80%, 7.33%–22.66%, and 11.07%–22.78%, respectively. Under the IP and MP planting patterns, pre-sowing B0 significantly increased by 0.11%–9.00% and 0.20%–5.70% compared to B10 and B20, respectively. Furthermore, under the IP planting pattern, B0, B10, and B20 significantly increased by 7.5%–26.64%, 16.79%–24.14%, and 13.49%–24.14%, respectively.

[0033] As shown above, intercropping can significantly increase the total nitrogen content in the shallow soil layer (0-60cm). Moreover, the total nitrogen content in the shallow soil layer under different planting patterns was significantly increased by biochar B10 compared to B0 treatment. This indicates that biochar has a good adsorption effect on the total nitrogen content of the soil, which is beneficial to meeting the nitrogen requirements of crops during their growth and development.

[0034] Example 2: The application of biochar in intercropping to nitrate nitrogen in soil.

[0035] Table 2 shows the effects of biochar and planting patterns on soil nitrate nitrogen content in the 0-160cm soil layer: The effects of planting pattern, biochar level, and planting pattern × biochar level on soil nitrate nitrogen content in the 0-160cm soil layer during the flowering and harvesting stages of flax and peas were significantly different. The planting pattern × biochar level (T×B) showed an interactive effect on soil nitrate nitrogen content in the 0-20cm and 80-140cm soil layers during the flowering stage and in the 0-20cm, 60-80cm, and 120-160cm soil layers during the harvesting stage. Before sowing, under the IF planting pattern, B10 significantly increased the soil nitrate nitrogen content in the 60-80cm soil layer by 40.6% and 56.96% compared to B0 and B20, respectively. During the flowering stage, under the IF planting pattern, the B10 treatment significantly increased the soil nitrate nitrogen content in the 0-20cm soil layer by 116.40% and 253.40% compared to B0 and B20, respectively. Under the IF planting pattern, treatment B20 significantly increased the nitrate nitrogen content in the 60-100cm soil layer by 279.60%–393.15% compared to treatment B0. Under the IP planting pattern, treatment B20 significantly increased the nitrate nitrogen content in the 100-140cm soil layer by 60.67%–144.90% and 126.70%–256.20% compared to B0 and B10, respectively. At harvest time, under the IP planting pattern, treatments B10 and B20 significantly increased the nitrate nitrogen content in the 0-20cm soil layer by 49.01% and 34.03%, respectively, compared to treatment B0.

[0036] like Figure 2As shown, biochar and planting patterns significantly increased the nitrate nitrogen content in the 0-160cm soil layer under all planting patterns, with intercropping showing higher levels than monoculture. In MF and IF, the pre-sowing biochar B10 treatment increased nitrate nitrogen content by 1.46% and 6.69% compared to the B0 treatment, respectively, and the B10 treatment resulted in a more uniform distribution of nitrate nitrogen content in the 0-60cm level. In terms of soil layer distribution, the nitrate nitrogen content in the 0-60cm and 100-160cm soil layers was higher than that in the 60-100cm soil layer, and this trend weakened at harvest. Comparisons of flax and pea before sowing, at flowering, and at harvest revealed significant differences in the impact of different biochar levels on the nitrate nitrogen content in the 0-160cm soil layer. Before sowing, the IP planting pattern increased nitrate nitrogen content by 20.46%–37.70% (B10) and 27.08%–45.27% (B20) compared to the MP planting pattern. At harvest time, biochar treatment under the IF planting mode increased biochar yield by 21.77%–52.00% (B10) and 25.06%–56.10% (B20) respectively compared to the MF planting mode; biochar treatment under the IP planting mode increased biochar yield by 28.79%–84.79% (B10) compared to the MP planting mode.

[0037] As shown above, intercropping significantly increases soil nitrate nitrogen in the 0-160cm soil layer at all stages compared to monocropping, and the effects of planting pattern and biochar level on soil nitrate nitrogen retention differ. B10 increases soil nitrate nitrogen content in the 0-20cm soil layer during the flowering period of intercropped flax and the harvest period of intercropped peas, while B20 treatment significantly increases soil nitrate nitrogen content in the 100-160cm (deep) soil layer during the flowering period of intercropped flax and intercropped peas. This indicates that biochar can increase the accumulation of soil nitrate nitrogen in different soil layers, significantly reduce the risk of nitrate nitrogen loss, reduce the leaching loss of water-soluble ions such as nitrate nitrogen, and delay the migration and transformation time.

[0038] Table 2. Effects of biochar and planting patterns on nitrate nitrogen content in the 0-160cm soil layer (mg·kg⁻¹) -1 )

[0039]

[0040] Note: ns, *, and ** indicate that the p-values ​​are not significant, significant, or highly significant at p < 0.05, p < 0.01, or p < 0.001, respectively. The means following different letters in the same column show significant differences at p < 0.05. The same applies to the following table.

[0041] Example 3: Application of biochar in soil under monoculture planting mode to ammonium nitrogen.

[0042] Table 3 shows the effects of biochar and planting patterns on the ammonium nitrogen content in the 0-160cm soil layer: The effects of planting pattern, biochar level, and planting pattern × biochar level on the ammonium nitrogen content in the 0-160cm soil layer during the flowering and harvesting stages of flax and pea differed significantly. The planting pattern × biochar level (T×B) showed an interaction effect on the ammonium nitrogen content in the 0-40cm and 60-80cm soil layers during the flowering stage, while after harvest, it showed an interaction effect in the 20-60cm and 120-160cm soil layers. During the flowering stage, under the IP planting pattern, B10 significantly increased the ammonium nitrogen content in the 0-20cm soil layer by 15.50% and 34.90% compared to B0 and B20 treatments, respectively; under the MP planting pattern, B20 and B10 significantly increased the ammonium nitrogen content in the 0-20cm soil layer by 50.70% and 28.00% compared to B0, respectively. With increasing soil depth, the ammonium nitrogen content in the 60-100cm soil layer showed significant changes, especially during the flowering period. Specifically, under the IP planting model, biochar treatment B10 significantly increased the ammonium nitrogen content in the 40-60cm soil layer by 24.40% and 28.90% compared to B0 and B20, respectively. Under the MP planting model, B20 significantly increased the ammonium nitrogen content in the 60-80cm soil layer by 30.40% and 53.50% compared to B0 and B10, respectively. Under the MF planting model, B10 significantly increased the ammonium nitrogen content in the 80-100cm soil layer by 18.10% and 20.40% compared to B0 and B20, respectively. Under the IF and MP planting models, B10 significantly increased the ammonium nitrogen content in the 80-100cm soil layer by 16.30% and 21.20% compared to B20, respectively. At harvest time, under the IP planting model, the B10 treatment significantly increased the soil ammonium nitrogen content in the 80-100cm and 100-120cm soil layers by 148.47% and 80.15% respectively compared to the B20 treatment, and the B10 treatment significantly increased the soil ammonium nitrogen content in the 140-160cm soil layer by 86.87% and 92.71% respectively compared to the B0 and B20 treatments. Under the MP planting model, the B20 treatment significantly increased the soil ammonium nitrogen content in the 120-140cm soil layer by 33.64% compared to the B10 treatment, and the B10 and B20 treatments significantly increased the soil ammonium nitrogen content in the 140-160cm soil layer by 31.63% and 33.88% respectively compared to the B0 treatment.

[0043] like Figure 3As shown: The effects of biochar and planting patterns on the vertical distribution of ammonium nitrogen content in soil profiles: Biochar treatment significantly increased the ammonium nitrogen content in the 0-160cm soil layer under different planting patterns, with the monoculture planting pattern showing higher levels than the intercropping planting pattern before sowing and after harvest. At the flowering stage, the ammonium nitrogen content in the MF treatment (B0) increased by 2.21% compared to the IF treatment. After harvest, the ammonium nitrogen content in the MP treatment increased by 114.37% and 106.47% compared to the IP treatment (B0 and B10), respectively. Furthermore, under the biochar B10 treatment, the ammonium nitrogen content was more evenly distributed at the 100-160cm level. In terms of soil layer distribution, the ammonium nitrogen content in the 0-60cm and 100-160cm soil layers was higher than that in the 60-100cm soil layer, and this distribution trend weakened after harvest. Comparisons between flax and pea before sowing, at the flowering stage, and after harvest revealed significant differences in the ammonium nitrogen content in the 0-160cm soil layer due to different biochar application levels. Before sowing, biochar treatment in MP (medium-fermented) mode increased biochar content by 7.10%–10.80% (B10) and 10.60%–14.40% (B20) compared to IP (intra- ...

[0044] As can be seen from the above, monoculture can significantly increase the ammonium nitrogen content in the 0-160cm soil layer compared with intercropping, and biochar B10 treatment can effectively increase the ammonium nitrogen content in the shallow soil, showing good adsorption capacity. This demonstrates that biochar can significantly reduce the risk of ammonium nitrogen loss and is beneficial to crop growth and development.

[0045] Table 3. Effects of biochar and planting patterns on soil ammonium nitrogen content in the 0-160cm soil layer (mg·kg) -1 )

[0046]

[0047] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of carrying out the invention as currently considered, or those features that are not relevant to implementing the invention) may be omitted.

[0048] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0049] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

Claims

1. A method of biochar application in dryland agriculture, characterized in that, Comprising the following steps: S1, in the arid region farmland, using single planting mode or intercropping planting mode, and applying biochar; the application amount of the biochar is set as three levels: 0 t hm -2 , adding 10 t hm -2 biochar, adding 20 t hm -2 biochar; the single planting mode is single planting of sesame or single planting of pea, and the intercropping planting mode is intercropping of sesame and pea; S2, in the seedling stage, flowering stage and harvest period of the flax crop, the soil samples of 0-160 cm soil layer are collected, and the sampling is stratified every 20 cm. The single flax is sampled between the two rows of the sowing zone, the single pea is sampled between the two plants with uniform growth in the same row, and the intercropping is sampled by selecting two points in the same area of flax and pea respectively and sampling simultaneously, then mixing uniformly as a soil sample; after sampling, the soil samples are mixed uniformly, air-dried, and the contents of total nitrogen, nitrate nitrogen and ammonium nitrogen in the soil are determined; S3, intercropping sesame and intercropping peas under different planting patterns can significantly improve the total nitrogen content of 0-60 cm soil. Compared with the treatment without adding biochar, the total nitrogen content of 0-60 cm soil is increased by 10 t·hm -2 Under the treatment of biochar, biochar significantly reduces the total nitrogen content of 60-160 cm soil, and the better the adsorption effect of biochar on soil total nitrogen content, the more conducive to the nitrogen demand of crops during growth and development; The intercropping mode significantly increased the soil nitrate nitrogen content in 0-160 cm soil layer compared with the single cropping mode, and the addition of 10 t·hm -2 Biochar treatment significantly increased the accumulation of soil nitrate nitrogen content of sunflower and pea, and the addition of 10 t·hm -2 Biochar treatment can increase the soil nitrate nitrogen content in 0-20 cm soil layer, and has good adsorption capacity, and the addition of 20 t·hm -2 Biochar treatment can significantly increase the soil nitrate nitrogen content in 100-160 cm soil layer, indicating that the addition of biochar has the best adsorption effect on ammonium nitrogen in soil, can significantly reduce the leaching risk of ammonium nitrogen, can reduce the leaching loss of water-soluble ions of nitrate nitrogen, and delay the migration and transformation time; The single cropping mode significantly increased the soil ammonium nitrogen content in 0-160 cm soil layer than the intercropping mode, and the soil ammonium nitrogen content was 10 t·hm -2 Biochar treatment significantly increased the soil ammonium nitrogen accumulation of sun hemp and pea, and improved the soil ammonium nitrogen content in 0-20 cm soil layer, and had better adsorption capacity, while the addition of 20 t·hm -2 Biochar treatment could significantly improve the soil ammonium nitrogen content in 120-160 cm soil layer, indicating that the planting mode and the different application amount of biochar had different effects on the retention effect of ammonium nitrogen in soil. The addition of biochar had the best adsorption effect on soil ammonium nitrogen, which could significantly reduce the leaching risk of ammonium nitrogen, and was beneficial to the growth and development of crops.

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