A method for constructing subsurface organic matter functional zones in sloping farmland based on manure-inducing straw return.

Abstract

This invention discloses a method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-inducing straw return, relating to the fields of soil improvement and water and soil conservation. Addressing the core pain point of topsoil stripping and erosion in sloping farmland, this invention utilizes an engineered scheme of manure-inducing straw return, which can increase the straw degradation rate by 30%–60% compared to conventional straw return techniques, significantly shortening the decomposition cycle. Within a single crop growing season, it can increase the organic matter content of the subsurface soil in sloping farmland by 20%–50%, simultaneously optimizing soil aggregate structure, enhancing soil water and fertilizer retention and erosion resistance, and effectively mitigating the risks of nitrogen competition and yield reduction during the seedling stage caused by straw return. This scheme can restore corn yield to the level of unstripped plots under erosion conditions with 20cm of topsoil stripping, achieving synergistic promotion of soil remediation and stable crop yield.

Description

Technical Field

[0001] This invention relates to the field of soil improvement and water and soil conservation technology for sloping farmland, specifically to a method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-induced straw return to the field. Background Technology

[0002] Sloping farmland is an important type of agricultural land in the hilly and mountainous areas of southwest and south my country. This type of farmland typically features steep slopes, shallow soil layers, poor structural stability, and severe soil erosion. Under the combined effects of long-term rainfall runoff, gravity erosion, and improper farming practices, the topsoil of sloping farmland is prone to continuous stripping, leading to partial or complete loss of the topsoil and exposure of the subsoil and even the subsurface soil. The exposed subsoil generally suffers from low organic matter content, severely damaged aggregate structure, unreasonable pore distribution, and weak water and fertilizer retention capacity, seriously hindering the downward extension of crop roots and the restoration of soil productivity. Therefore, under the background of sloping farmland erosion, how to rapidly increase the organic matter content of the subsoil and rebuild its structural function has become a key technical problem that urgently needs to be solved in the field of improving the quality of sloping farmland and soil and water conservation.

[0003] Corn stalks, as one of the most important renewable organic resources in agricultural production, are rich in cellulose, hemicellulose and lignin, and are an important carbon source for supplementing soil organic matter. Currently, the straw return technology promoted in my country mainly includes straw crushing and covering, plowing and burying, and application of microbial composting agents. However, in the erosion environment of sloping farmland, conventional straw return technology still faces many limitations, mainly in the following aspects: (1) Low straw decomposition rate. Corn stalks have a high carbon-nitrogen (C / N) ratio and strong structural stability. Under the condition of lack of exogenous nitrogen source and participation of highly active microorganisms, their decomposition cycle is long and it is difficult to release usable nutrients in the short term; (2) Easily triggers nitrogen competition and seedling yield reduction risk. The competition of microorganisms for inorganic nitrogen during straw decomposition may lead to "pseudo-nitrogen deficiency" in the soil, inhibiting early crop growth; (3) Low organic matter conversion efficiency. If straw cannot quickly complete the mineralization and humification process, it is difficult to convert into stable soil organic matter components within a crop growing season, and the fertilizer utilization rate is limited; (4) Poor spatial stability under sloping farmland conditions. Straw returned to the surface is easily eroded or lost by slope runoff, making it difficult to form a stable organic matter accumulation structure in the soil.

[0004] Livestock and poultry manure, rich in soluble organic carbon, nitrogen sources, and diverse microbial communities, has been widely used in recent years to improve soil physicochemical properties and promote organic matter accumulation. The rational application of livestock and poultry manure during straw return to the field can significantly improve straw decomposition rate and humification efficiency, which is conducive to the formation of stable soil aggregates, enhances soil water and fertilizer retention capacity, and reduces the risk of slope erosion. However, in existing technologies, manure is often used as a single nutrient source or simply applied in synergy with straw on the surface. Its application layer, spatial structure, and mode of action lack a systematic design tailored to the erosion characteristics of sloping farmland, making it difficult to fully utilize the stimulating effect of manure on straw transformation, and the stability of the restoration effect is insufficient. Especially under conditions of significant topsoil stripping on sloping farmland, existing straw or manure application techniques still struggle to form a stable, orderly, and sustainable organic matter accumulation structure in the subsoil, restricting the restoration of the productivity and ecological functions of sloping farmland.

[0005] In summary, existing technologies lack systematic remediation solutions for topsoil stripping / erosion scenarios on sloping farmland, and cannot achieve the synergistic goals of rapid straw humification, targeted enrichment of subsurface organic matter, and stable crop yield. There is an urgent need to propose a new manure-inducing straw return technology that can construct a stable organic matter functional structure in the subsurface of sloping farmland in an engineered manner, so as to provide a new technical path for the sustainable use of agriculture and soil and water conservation on sloping farmland. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-inducing straw return.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-inducing straw return is provided, which includes the following steps: S1: Determine the degree of topsoil stripping on the target sloping farmland and reconstruct the topsoil layer based on the determination results; S2: Add straw and activating material to the reconstructed tillage layer and bury the straw and activating material in the tillage layer; S3: After the soil is mixed and buried, the soil moisture is regulated to maintain the soil moisture content of the topsoil at 50-70% of the field capacity. Under natural or artificial watering conditions, the soil is allowed to mature and activate for 7-15 days. S4: After the maturation period, corn is mechanically sown, and field management such as fertilization, irrigation, and weeding is carried out according to conventional agronomic practices.

[0008] Furthermore, in step S1, the topsoil stripping depth is divided into light stripping, medium stripping, and heavy stripping. Light stripping is defined as a topsoil stripping depth of 0-10cm, medium stripping as a topsoil stripping depth of 10-20cm, and heavy stripping as a topsoil stripping depth of ≥20cm. For sloping farmland with medium and heavy stripping, the topsoil layer is reconstructed to 15-20cm by shallow plowing or rotary tillage.

[0009] Furthermore, in step S2, the ratio of straw to activating material is such that the C / N ratio of the tillage layer is 25-30.

[0010] Furthermore, in step S2, the straw used is 3-15cm in length, and the dry weight of the straw is 5600kg / hm. 2 .

[0011] Furthermore, in step S2, the activating material is well-rotted or semi-rotted livestock and poultry manure, which is any one or a combination of two or more of cow manure, pig manure, sheep manure, chicken manure, and duck manure.

[0012] Furthermore, in step S2, the amount of manure applied is 8300 kg / hm². 2 .

[0013] Furthermore, in step S4, the maturation and activation treatment lasts for 10 days, and the soil moisture content in the topsoil is maintained at 60% of field capacity.

[0014] Furthermore, in step S2, the straw and activating materials are distributed in the soil layer of 15-35cm by deep loosening, deep turning or layered tillage.

[0015] The present invention also provides the application of the above-mentioned method in improving soil quality on sloping farmland, soil and water conservation, and stabilizing crop yields in dryland areas.

[0016] The beneficial effects of this invention are as follows: This invention addresses the core challenge of topsoil stripping and erosion on sloping farmland. Through an engineered solution that utilizes manure to stimulate straw return to the field, it can increase the straw degradation rate by 30%–60% compared to conventional straw return techniques, significantly shortening the decomposition cycle. Within a single crop growing season, it can increase the organic matter content of the subsoil layer on sloping farmland by 20%–50%, simultaneously optimizing soil aggregate structure, enhancing soil water and fertilizer retention and erosion resistance, and effectively mitigating the risks of nitrogen competition and reduced yields during the seedling stage caused by straw return. This solution can restore corn yields to the level of unstripped plots even under erosion conditions with 20cm of topsoil stripping, achieving synergistic progress in soil remediation and stable crop yields. The fully engineered design is adaptable to the operating conditions of small and medium-sized agricultural machinery in the hilly and mountainous areas of Southwest China, exhibiting strong adaptability to sloping farmland with varying degrees of erosion, and possessing excellent operability and potential for large-scale promotion. Attached Figure Description

[0017] Figure 1 This is a comparison chart of the content of water-stable aggregates in soil from different treatment groups in the examples; Figure 2 This is a comparison chart of maize yields in different treatment groups in the examples. Detailed Implementation

[0018] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0019] Example This embodiment was conducted on sloping farmland in Xiaoxin Village, Yuanmou County, in the dry-hot river valley region of Southwest China. Cow dung was used as the activating material to construct a functional zone of subsurface organic matter in the sloping farmland with straw return. In specific implementation, any one of pig manure, sheep manure, chicken manure, or duck manure, or a combination of two or more of cow manure, pig manure, sheep manure, chicken manure, or duck manure, can also be used. The specific steps include the following: (1) Topsoil stripping treatment: Artificial stripping was used to simulate erosion of the topsoil of the experimental sloping farmland. Three gradients were set with stripping depths of 0cm, 10cm and 20cm to expose the subsurface soil and form the cultivated layer. Among them, 10cm stripping was medium stripping and 20cm stripping was heavy stripping. The cultivated layer was reconstructed to 20cm by rotary tillage for both treatment groups.

[0020] (2) Straw treatment: After corn harvest, the corn stalks are crushed to 5-8cm and then processed at a rate of 5600kg / hm. 2 The dry mass was evenly distributed in each experimental treatment group block.

[0021] The "subsurface organic matter functional zone" constructed in this invention is located at a depth of 10–30 cm below the tillage layer, with an effective thickness of 10–20 cm. (Based on 1 hm²) 2 The volume of soil in the functional zone of sloping farmland is approximately V = 10000 m³. 2 ×0.12m=1200m 3 Combined with the common bulk density of subsoil in sloping farmland (1.2~1.4 g / cm³), 3 The equivalent soil mass of the functional zone is approximately: M=1200m 3 ×1.3t / m 3 ≈1560t; For subsurface soil organic matter to form a stable structure and significantly improve the proportion of water-stable aggregates, an organic carbon input of no less than 0.15%–0.20% of the soil mass is required. Assuming an average straw organic carbon content of 40%, if the straw return rate is 5600 kg / hm²...2 The input organic carbon is: Cinput = 5600 × 0.40 = 2240 kg; the corresponding increase in soil organic carbon in the functional zone is approximately: 2240 ÷ 1560000 × 100% ≈ 0.14%; this value is within the critical range for activating subsurface structure, which can trigger aggregate formation without causing anaerobic decomposition or nutrient imbalance due to excessive carbon input. The straw input is selected as 5600 kg / hm². 2 At that time, it accounts for about 65% to 75% of the annual corn stalk production, which is compatible with the current mechanized crushing-plowing-deep tillage collaborative operation capacity. No additional changes to the stalk treatment system are required, making it highly scalable for engineering applications. Therefore, the straw return rate is 5600 kg / hm². 2 The optimal parameters were determined under the triple constraints of structural excitation threshold, spatial matching, and engineering feasibility.

[0022] (3) Manure application: at 8300 kg / hm 2 Apply well-rotted cow manure and manually mix it with the surface straw. The ratio of dry straw to fresh manure is 1:1.48, and the overall C / N ratio of the system is adjusted to about 28.

[0023] The C / N ratio of corn stalks is typically 60-80. Directly returning them to the field can easily cause nitrogen starvation in microorganisms, inhibiting stalk decomposition and organic matter conversion. The engineering-recognized optimal C / N ratio range for microbial decomposition is 25-30. Assuming a stalk quantity of 5600 kg / hm²... 2 If the carbon content is 40%, then the carbon input is 2240 kg. If the target C / N ratio is 28, then the required nitrogen is approximately: Nreq = 2240 ÷ 28 ≈ 80 kg. Based on common livestock and poultry manure (well-rotted), its total nitrogen content is typically 0.9%~1.2%. Taking the median value of 1.0%, the manure application rate to meet the nitrogen requirements for straw decomposition should be: 80 ÷ 0.01% = 8000 kg / hm². 2 Considering factors such as nitrogen loss, microbial fixation, and asynchronous release in sloping farmland environments, the engineering calculation needs to be appropriately increased, and the final value is determined to be 8300 kg / hm². 2 This invention emphasizes a "manure-inducing" rather than a "manure-dominant" approach, with a target concentration of 8300 kg / hm². 2 The application rate was significantly lower than that of conventional organic fertilizers for soil improvement (usually ≥15000 kg / hm). 2 Its main function is to provide a usable nitrogen source to initiate decomposition, activate microbial metabolism, and promote the conversion of straw carbon into stable organic matter, rather than directly accumulating organic matter, which is fundamentally different from existing technologies.

[0024] (4) Tillage and soil mixing: Use a rotary tiller to mix pig manure and crushed straw into the 15-20cm tillage layer, so that it is concentrated in the 5-20cm subsurface soil area, ensuring that the straw and manure are fully and evenly in contact.

[0025] (5) Management during the maturation period: Maintain the soil moisture content of the topsoil at 60% of the field capacity by drip irrigation and let it stand for 10 days to mature.

[0026] (6) Corn sowing: After the maturation period, corn is planted by mechanical strip sowing. Nitrogen, phosphorus and potassium compound fertilizer is applied as base fertilizer, and the amount of fertilizer applied is the same as that of conventional planting in the local area.

[0027] (7) Field management: The entire growth period adopts the plastic film covering + drip irrigation mode, and irrigation, weeding and topdressing are carried out according to local conventional agronomic measures.

[0028] This embodiment also includes two control treatments: Blank control: No straw or manure was added; only the same tillage, sowing, and field management were performed. Single straw return to field treatment: based only on 5600 kg / hm 2 Add corn stalks, and the remaining steps are the same as in this embodiment; Soil organic carbon content was measured under different gradients and treatment methods, and the results are shown in Table 1. Table 1

[0029] Table 1 shows that, within one maize growing season, compared to the control plot, in the 10cm topsoil stripping area, straw return alone increased the soil organic carbon content in the 0-10cm and 10-20cm layers by 9.5% and 12.7%, respectively, while manure-induced straw return increased the soil organic carbon content in the 0-10cm and 10-20cm layers by 49.2% and 19.0%, respectively. In the 20cm topsoil stripping area, straw return alone increased the soil organic carbon content in the 0-10cm and 10-20cm layers by 33.3% and 22.9%, respectively, while manure-induced straw return increased the soil organic carbon content in the 0-10cm and 10-20cm layers by 52.6% and 31.3%, respectively.

[0030] Simultaneously, the particle size distribution of water-stable aggregates in the soil was measured, and the results are as follows: Figure 1 As shown; by Figure 1It can be seen that manure-induced straw return significantly increased the content of >0.25mm water-stable aggregates in the topsoil stripped from the soil, and significantly enhanced soil structural stability. In the 10cm topsoil stripped area, under straw return alone, the content of >0.25mm water-stable aggregates in the 0-10cm and 10-20cm sections increased by 13.5% and 3.9%, respectively, while under manure-induced straw return, the content of >0.25mm water-stable aggregates in the 0-10cm and 10-20cm sections increased by 20.6% and 20.0%, respectively. In the 20cm topsoil stripping zone, when only straw was returned to the field, the content of >0.25mm water-stable aggregates in the 0-10cm and 10-20cm sections increased by 11.3% and 0.4%, respectively. However, when manure was used to stimulate straw return to the field, the content of >0.25mm water-stable aggregates in the 0-10cm and 10-20cm sections increased by 39.3% and 31.2%, respectively.

[0031] In addition, the yield of sweet corn was also statistically analyzed, and the results are as follows: Figure 2 As shown, by Figure 2 It can be seen that manure-induced straw return to the field can significantly increase corn yield in the erosion test block, basically reaching the yield level of the unremoved topsoil.

Claims

1. A method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-inducing straw return, characterized in that, The following steps are used: S1: Determine the degree of topsoil stripping on the target sloping farmland and reconstruct the topsoil layer based on the determination results; S2: Add straw and activating material to the reconstructed tillage layer and bury the straw and activating material in the tillage layer; S3: After the soil is mixed and buried, the soil moisture is regulated to maintain the soil moisture content of the topsoil at 50-70% of the field capacity. Under natural or artificial watering conditions, the soil is allowed to mature and activate for 7-15 days. S4: After the maturation period, corn is mechanically sown, and field management such as fertilization, irrigation, and weeding is carried out according to conventional agronomic practices.

2. The method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-induced straw return, as described in claim 1, is characterized in that... In step S1, the topsoil is divided into light stripping, medium stripping and heavy stripping according to the stripping depth. Light stripping is the topsoil stripping depth of 0~10cm, medium stripping is the topsoil stripping depth of 10~20cm, and heavy stripping is the topsoil stripping depth of ≥20cm. For sloping farmland with medium and heavy stripping, the topsoil layer is reconstructed to 15~20cm by shallow plowing or rotary tillage.

3. The method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-induced straw return, as described in claim 1, is characterized in that... In step S2, the ratio of straw to activating material is such that the C / N ratio of the tillage layer is 25-30.

4. The method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-induced straw return, as described in claim 3, is characterized in that... In step S2, the straw used is 3-15cm in length, and the dry weight of the straw is 5600kg / hm. 2 .

5. The method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-induced straw return, as described in claim 4, is characterized in that... In step S2, the activating material is well-rotted or semi-rotted livestock and poultry manure, which is any one or a combination of two or more of cow manure, pig manure, sheep manure, chicken manure, and duck manure.

6. The method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-induced straw return, as described in claim 5, is characterized in that... In step S2, the amount of manure applied is 8300 kg / hm. 2 .

7. The method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-induced straw return as described in claim 1, characterized in that, In step S4, the maturation and activation treatment lasts for 10 days, and the soil moisture content in the topsoil is maintained at 60% of field capacity.

8. The method for constructing a functional zone of subsurface organic matter in sloping farmland based on manure-induced straw return, as described in claim 1, is characterized in that... In step S2, the straw and activating materials are distributed in the soil layer of 15-35cm by deep loosening, deep turning or layered tillage.

9. The application of the method described in any one of claims 1 to 8 in improving soil quality on sloping farmland, soil and water conservation, and stabilizing crop yields in dryland areas.

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