A method for improving soil by grain and grass rotation in a dry region of the loess plateau

Abstract

The present application belongs to the technical field of loess plateau rain-fed dry farming farmland soil improvement and ecological farming, and specifically discloses a loess plateau dry farming area grain-grass rotation soil fertilization method, which is provided with three sets of one-year local grain-grass rotation combinations of potato-oat, forage corn-pea and wheat-mulberry, and is matched with Gansu Dingxi loess plateau dry farming special crop varieties, unified nitrogen-phosphorus-potassium base fertilizer ratio and standardized sowing specifications. Two years of field positioning test verification proves that the present application can significantly improve the content of soil water stable large aggregates, reduce the aggregate damage rate, repair the degraded soil structure, year by year reduce the pH of the loess soil, alleviate the potential soil alkalization, continuously improve the organic carbon and nitrogen level of the cultivated land, improve the soil fertilizer retention and buffering capacity, and simultaneously realize multiple benefits of stable grain yield, high-quality forage supply and water and soil loss prevention and control, and the present application has high standardization degree and is suitable for large-area popularization and application in the loess plateau dry farming area of Gansu Dingxi.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement and ecological farming technology for rain-fed dryland farmland in the Loess Plateau. It relates to a method for improving soil fertility through crop rotation in the dryland areas of the Loess Plateau. Specifically, it is a standardized method for improving soil fertility through crop rotation that is suitable for the loess soil region of Dingxi, Gansu Province, and takes into account both grain production and forage supply. Background Technology

[0002] As a typical ecologically fragile area, the Loess Plateau's soil is mainly composed of loose loess parent material, with weak interparticle cementation and poor structural stability. Under the combined effects of long-term high-intensity farming and rainfall erosion, soil structure degradation has become increasingly prominent, manifested in a series of changes such as a decrease in the proportion of large aggregates, an increase in the proportion of micro-aggregates, fragmentation of pore structure, and an increase in soil bulk density. This structural deterioration directly weakens the soil's water retention capacity and reduces its resistance to erosion, making the soil prone to dispersion and loss under heavy rainfall conditions, and prone to compaction and cracking under drought conditions, exhibiting the typical characteristics of "erosion in rain and compaction in drought." At the same time, structural degradation also restricts crop root development and nutrient absorption, exacerbating soil fertility decline and soil erosion, becoming a core obstacle to the sustainable development of agriculture in the region. Coupled with the uneven spatial and temporal distribution of precipitation against the backdrop of climate change, this further amplifies the vulnerability and instability of soil structure. Against the backdrop of ecological protection and high-quality development in the Yellow River Basin, Loess Plateau agriculture faces the dual pressures of continuously declining arable land quality and rapidly increasing demand for grassland and livestock farming. Exploring sustainable farming models to address this predicament is therefore essential.

[0003] Compared to monoculture, crop rotation can balance soil nutrients and improve soil structure by relying on the root systems of diversified crops. The introduction of leguminous forage crops into grain-forage rotation can continuously input organic matter through root exudates and crop residues, promoting soil aggregate formation and simultaneously increasing soil organic carbon content and basic soil fertility. This is a sustainable path for ecological soil improvement in dryland areas. However, existing grain-forage rotation systems in dryland areas of the Loess Plateau have the following drawbacks: (1) The crop rotation pattern is simple, with only wheat-alfalfa long-cycle crop rotation. There is a lack of short-term crop rotation combinations that are suitable for rain-fed agriculture with one crop per year. There is no standardized crop rotation system for potatoes-oats or forage corn-peas. (2) There are no localized supporting technical specifications, and there are no standardized parameters such as special crop varieties suitable for Dingxi area, unified fertilization, and sowing row spacing and plant spacing. Farmers rely on experience for production, and the soil improvement effect is unstable. (3) The soil improvement evaluation system is incomplete. Only the single indicators of organic matter and crop yield are measured. The complete set of standardized indicators of soil aggregate composition and stability, soil pH, cation exchange capacity and other key indicators are not measured. Furthermore, the 0-20cm and 20-40cm layered soil tests are lacking, making it impossible to quantify the effects of soil alkalization improvement and aggregate structure repair. (4) There is a lack of multi-mode quantitative screening methods. The selection of crop rotation is based solely on subjective judgment of the merits of a single indicator. There is no comprehensive evaluation system of gray relational multi-indicators to objectively screen the optimal crop rotation scheme. (5) Existing technologies cannot simultaneously achieve multiple synergistic goals such as fertilization of arable land, stable grain production, supply of forage and soil and water conservation. Long-cycle alfalfa rotation results in insufficient grain output, rapid depletion of soil nutrients, and no forage output in grain-grain rotation, which cannot support the breeding industry, does not utilize the development of circular agriculture, and is difficult to match the needs of regional industrial development.

[0004] In view of the above-mentioned technical problems, this invention is proposed. Summary of the Invention

[0005] To address the shortcomings of existing dryland farming areas in the Loess Plateau, such as land degradation due to continuous cropping, a single crop rotation pattern for grain and forage, the lack of localized and standardized cultivation guidelines, insufficient soil improvement evaluation dimensions, and the inability to simultaneously meet the dual production needs of grain and forage, this invention provides a method for improving soil fertility through crop rotation in dryland farming areas of the Loess Plateau. This method utilizes three sets of localized one-crop-per-year crop rotation combinations, standardized cultivation parameters, a stratified multi-dimensional soil monitoring system, and a comprehensive evaluation method based on grey relational analysis to select the optimal corn-pea rotation pattern for forage. This simultaneously repairs soil aggregate structure, alleviates soil alkalization, and enhances soil fertility, achieving ecologically sustainable utilization of dryland farmland while simultaneously ensuring both grain production and forage supply.

[0006] The purpose of this invention is to provide a method for crop rotation and soil improvement in the dryland areas of the Loess Plateau, comprising the following steps: S1: Site Selection A plot of land in the dryland loess soil of Dingxi Loess Plateau, Gansu Province, where maize is continuously cropped, was selected and the land was uniformly prepared and divided into experimental plots. S2: Set planting treatment The plantation adopts a single-crop-per-year rain-fed cultivation method and a grain-forage rotation treatment. The area of ​​a single plot is 35m², and a 1m isolation strip is set between plots. S3: Unified application of base fertilizer The uniform base fertilizer application rate for all communities is: N 120 kg·hm² -2 P2O5 90 kg·hm -2 K2O 90 kg·hm -2 The fertilizers selected are urea, superphosphate, and potassium sulfate; S4: Standardized sowing Sowing is carried out uniformly every April, with supporting measures such as ridging and mulching, standardized row spacing and plant spacing for spot sowing / row sowing. S5: Layered Soil Sampling and Testing Soil samples were collected from two layers (0-20cm and 20-40cm) during the vigorous growth and maturity stages of the crop, respectively; the soil aggregate index R was measured. 0.25 WR 0.25MWD, GMD, PAD, ELT, as well as soil pH, organic carbon, total nitrogen, and cation exchange capacity; S6: Grey relational comprehensive evaluation: integrating soil physical and chemical indicators for comprehensive scoring.

[0007] Preferably, the forage rotation in step S2 is a potato-oat (PO) rotation, a forage corn-pea (MP) rotation, or a wheat-alfalfa (WA) rotation.

[0008] Preferably, step S2 adopts a corn-pea (MP) rotation pattern.

[0009] Preferably, the localized special varieties used in step S2 are: Dingshu No. 4 potato, Dajingjiu 23 for feed corn, Dingxi 40 wheat, Dingyan No. 2 oat, Dingwan No. 10 pea, and Gannong No. 5 alfalfa.

[0010] Preferably, the potato-oat (PO) rotation is as follows: In the first year, potatoes "Dingshu No. 4" are planted on 20cm high ridges covered with 1m black plastic film, with spot sowing, row spacing of 25cm, plant spacing of 30cm, sowing depth of 10-12cm, and sowing rate of 275kg / hm²; in the second year, oats "Dingyan No. 2" are sown in open fields with 20cm equal row spacing, sowing depth of 3-4cm, and sowing rate of 75kg / hm².

[0011] Preferably, the forage corn-pea (MP) rotation is as follows: in the current year, forage corn "Dajingjiu 23" is sown single seeds under a 1m white film, with a row spacing of 40cm, a plant spacing of 15cm, a sowing depth of 4-5cm, and a sowing rate of 30kg / hm²; in the following year, pea "Dingwan 10" is sown in rows with a 20cm row spacing, a sowing depth of 3cm, and a sowing rate of 105kg / hm².

[0012] Preferably, the wheat-alfalfa (WA) rotation is as follows: wheat "Dingxi 40" is sown in rows with a spacing of 20cm, a sowing depth of 3-4cm, and a sowing rate of 180kg / hm² in the current year; alfalfa "Ganong 5" is sown in rows with a spacing of 20cm, a sowing depth of 1-1.5cm, and a sowing rate of 12kg / hm² in the following year.

[0013] Preferably, after all crops are sown, the soil should be compacted in time, and drainage holes should be made every 50cm in the furrows. During the seedling stage, the film should be broken in time to release the seedlings, and the film holes should be sealed with fine soil to retain moisture.

[0014] Preferably, in step S5, the soil aggregates are determined by dry sieving to determine mechanically stable aggregates and by wet sieving to determine water-stable aggregates.

[0015] Preferred methods for determining soil chemical indicators in step S6 include: pH determination by potentiometry, organic carbon determination by potassium dichromate external heating method, total nitrogen determination by Kjeldahl method, and cation exchange capacity determination by hexaamminecobalt trichloride extraction-spectrophotometry.

[0016] Preferably, the method is applicable to rain-fed dryland farmland in Huangmian soil, Dingxi, Gansu Province, with an average annual rainfall of 350-600 mm and an average annual temperature of 5.7-7.7℃.

[0017] The beneficial effects of this invention are: (1) This invention simultaneously constructs three sets of crop rotation combinations suitable for one crop per year in the dryland farming area of ​​Dingxi, Gansu Province, filling the gap in the existing technology that only has a single long-cycle wheat-alfalfa rotation. Farmers can flexibly choose the rotation mode according to their needs for grain and forage.

[0018] (2) This invention is equipped with local special crop varieties in Dingxi, unified nitrogen, phosphorus and potassium base fertilizer ratio, and standardized sowing row spacing and plant spacing specifications, which solves the problems of traditional planting relying on experience, lack of standardized parameters and unstable soil improvement effect.

[0019] (3) This invention uses 0-20cm and 20-40cm double-layer soil sampling to fully measure the complete set of stability indicators of aggregates, plus pH, organic carbon, total nitrogen, and cation exchange capacity. It comprehensively quantifies the stratified improvement effect of crop rotation on soil structure, acid-base environment, and fertilizer retention buffer capacity, making up for the shortcomings of the single evaluation system.

[0020] (4) The invention has been verified by field plot experiments for two consecutive years. The MP rotation mode can significantly increase the content of water-stable large aggregates, MWD and GMD in the soil, reduce the aggregate destruction rate PAD, and enhance the soil's resistance to erosion and compaction. It can also reduce the pH of loess soil year by year, alleviate the soil alkalization trend, significantly increase soil organic carbon, total nitrogen and cation exchange capacity, and improve the fertility of cultivated land year by year.

[0021] (5) This invention simultaneously achieves multiple benefits such as soil fertility improvement, stable grain production, stable output of high-quality legume forage, and prevention and control of soil erosion. It is in line with the ecological protection and grain storage policies of the Yellow River Basin, and is suitable for the industrial development needs of the dryland farming area in Dingxi, Gansu Province. It is also convenient for large-scale standardized promotion. Attached Figure Description

[0022] Figure 1 This is a schematic diagram showing the content of mechanically stable aggregates under different treatments in 2024.

[0023] Figure 2 This is a schematic diagram showing the content of mechanically stable aggregates under different treatments in 2025.

[0024] Figure 3 This is a schematic diagram showing the stable agglomeration content in water under different treatments in 2024.

[0025] Figure 4 This is a schematic diagram showing the stable agglomeration content in water under different treatments in 2025.

[0026] Figure 5Schematic diagram of soil macroaggregate content and water-stable aggregate content under different treatments in 2024 and 2025 (A: vigorous growth period, B: harvest period).

[0027] Figure 6 This diagram illustrates the average weight diameter and geometric mean diameter of soil aggregates under different treatments in 2024 and 2025 (A: vigorous growth period, B: harvest period).

[0028] Figure 7 Schematic diagram of soil aggregate destruction rate and unstable aggregate index under different treatments in 2024 and 2025 (A: vigorous growth period, B: harvest period).

[0029] Figure 8 This diagram illustrates soil pH under different treatments in 2024 and 2025 (A: vigorous growth period, B: harvest period).

[0030] Figure 9 This diagram illustrates the total nitrogen content in soil under different treatments in 2024 and 2025 (A: vigorous growth period, B: harvest period).

[0031] Figure 10 This diagram illustrates the soil organic carbon content under different treatments in 2024 and 2025 (A: vigorous growth period, B: harvest period).

[0032] Figure 11 This diagram illustrates the soil cation exchange capacity under different treatments in 2024 and 2025 (A: vigorous growth period, B: harvest period). Detailed Implementation

[0033] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0034] In this invention, the crop rotation is a potato-oat (PO) rotation, a forage corn-pea (MP) rotation, or a wheat-alfalfa (WA) rotation.

[0035] The three crop rotation systems mentioned above have distinct capabilities and applicable plots: MP has the best overall soil improvement performance and a balanced grain and forage yield; PO is suitable for short-term soil fertilization in major potato-producing areas; WA has a weak soil erosion resistance improvement effect and is only suitable for plots with long-term grass planting and no need for high-intensity soil improvement.

[0036] Potato-oat (PO) rotation: In the first year, potatoes "Dingshu No. 4" are planted on 20cm high ridges covered with 1m black plastic film, with spot sowing, row spacing of 25cm, plant spacing of 30cm, sowing depth of 10-12cm, and seeding rate of 275kg / hm²; in the second year, oats "Dingyan No. 2" are sown in open fields with 20cm equal row spacing, sowing depth of 3-4cm, and seeding rate of 75kg / hm². Forage corn-pea (MP) rotation: In the current year, forage corn "Dajingjiu 23" is sown single seeds under 1m white plastic film, with a row spacing of 40cm, a plant spacing of 15cm, a sowing depth of 4-5cm, and a sowing rate of 30kg / hm²; in the following year, pea "Dingwan 10" is sown in rows with a 20cm row spacing, a sowing depth of 3cm, and a sowing rate of 105kg / hm². Wheat-alfalfa (WA) rotation: In the first year, wheat "Dingxi 40" is sown in rows with a spacing of 20cm, a sowing depth of 3-4cm, and a sowing rate of 180kg / hm²; in the second year, alfalfa "Ganong 5" is sown in rows with a spacing of 20cm, a sowing depth of 1-1.5cm, and a sowing rate of 12kg / hm². After all crops are sown, compact the soil promptly. Make drainage holes every 50cm in the furrows. When seedlings emerge, promptly break the film to release the seedlings and seal the film holes with fine soil to retain moisture.

[0037] The three-system crop rotation system features standardized operations for seedling emergence, weeding, and green pest and disease control, ensuring uniform crop growth and preventing human disturbance from affecting soil testing results. Mulching and Seedling Management: PO potatoes and MP forage corn are sown on the mulch. When the seedlings have 2 leaves and 1 heart, the mulch is manually broken in a cross shape and the seedlings are released. After the seedlings are released, the openings of the mulch are sealed with fine soil. WA wheat is fully covered with soil and the seedlings emerge on their own without the need for manual seedling release. Oats, peas, and alfalfa are planted in open fields without mulching, and the seedling release process is omitted. Damaged mulch should be repaired and drainage holes in furrows should be cleared in a timely manner after strong winds and rain.

[0038] Weed control: Apply metolachlor as a pre-emergence pretreatment spray after sowing and before seedling emergence; perform manual shallow weeding when the crop has 4 leaves and is branching, with a weeding depth not exceeding 3cm; during the seedling stage, only manual weeding is used, and no chemical herbicides are used throughout the process to avoid pesticide residues affecting the quality of forage.

[0039] Pest and disease control: Based on the local pest and disease types of each crop, apply low-toxicity green pesticides during the corresponding key growth stages. Potatoes are protected against late blight, corn is protected against corn borer, peas are protected against powdery mildew, wheat is protected against stripe rust, and oats and alfalfa are protected against aphids. All pesticide application is stopped 30 days before harvest to ensure the safety of grain and forage.

[0040] In this invention, the soil aggregate index R is determined. 0.25 WR 0.25 The methods for measuring MWD, GMD, PAD, ELT, as well as soil pH, organic carbon, total nitrogen, and cation exchange capacity are as follows: (1) Index collection: Soil physical index R was collected from the 0-20cm and 20-40cm soil layers. 0.25 WR 0.25 The original data matrix of 5 treatments × 10 indicators was constructed, including MWD, GMD, PAD, ELT, and chemical indicators such as pH, organic carbon, total nitrogen, and cation exchange capacity. (2) Data standardization: Positive and negative indicators are differentiated by using the extreme value method for dimensionless conversion, and the numerical range is unified from 0 to 1; the positive indicator is R 0.25 WR 0.25 The following are the indicators: MWD, GMD, organic carbon, total nitrogen, and cation exchange capacity; negative indicators are PAD, ELT, and pH, as detailed in the table below. (3) Construct the optimal reference sequence: take the maximum value of each index after standardization as the theoretically optimal soil state parent sequence; (4) Difference calculation: Solve for the absolute difference between each processing index and the optimal sequence to obtain the global two-level minimum difference and the two-level maximum difference; (5) Calculation of correlation coefficient for single index: Set the resolution coefficient ρ=0.5, and substitute it into the correlation coefficient formula to obtain the correlation coefficient for each index; (6) Weighted comprehensive scoring: The comprehensive grey relational degree of each treatment is obtained by weighting and summing with fixed index weights. The higher the relational degree value, the better the soil comprehensive improvement effect. Based on the relational degree value, the best scheme is selected by ranking the advantages and disadvantages of each crop rotation mode.

[0041] The specific calculation steps are as follows: Step 1: Construct the original evaluation matrix Suppose there are m processes (m=5) and n evaluation metrics (n=10), and the original data matrix is ​​as follows: $ X= mn : The measured value of the m-th process and the n-th indicator.

[0042] Step 2: Dimensionless standardization of indicators (eliminating dimensions and distinguishing between positive and negative directions) (1) Standardization of positive indicators (the larger the better: aggregates, nutrient fractions) max(x n ): The maximum value of all processed indicators for the nth index; min(x) n ): The minimum value of all nth indicators.

[0043] (2) Standardization of negative indicators (the smaller the better: pH, PAD, ELT) After standardization, all numerical ranges are unified to [0,1], and the closer the value is to 1, the better the improvement effect.

[0044] Step 3: Determine the reference optimal sequence (parent sequence) Optimal sequence X0={ , ,…, For each indicator, the standardized maximum value is taken: =MAX( , ,…, ) This represents the theoretically optimal soil improvement state, and the correlation between all treatments and this optimal sequence is calculated.

[0045] Step 4: Calculate the difference sequence, the minimum difference of two levels, and the maximum difference of two levels. (1) Absolute difference sequence: the absolute value of the difference between each treatment and the optimal sequence. Δmn=∣ - | (2) Minimum difference of level one: the minimum difference within each column of indicators (3) Two-level minimum difference: The global minimum value of all differences Δmin = (4) Maximum difference between two levels: the global maximum value of all differences Δmax = Step 5: Calculate the correlation coefficient ξmn for a single indicator ξmn= ρ = 0.5 resolution coefficient; ξmn ∈ (0,1], the larger the value, the closer the processing is to the optimal level under this index.

[0046] Step 6: Calculate the weighted overall grey relational degree ri The weighted sum is calculated by combining the preset indicator weights wj (∑wj=1): ri= The larger the ri is, the better the comprehensive soil improvement effect of the crop rotation mode; sorting by ri from largest to smallest, we get the ranking of the superiority and inferiority of each treatment (corresponding to the ranking results in Table 5 below).

[0047] Example 1 A method for improving soil fertility through crop rotation in the dryland farming area of ​​the Loess Plateau includes the following steps: S1: Site Selection The experimental plots were selected in Xizhai Village, Xiangquan Town, Anding District, Dingxi City, Gansu Province. The soil was yellow cotton soil and the previous crop was maize in continuous cropping for many years. The land was uniformly prepared and divided into experimental plots. S2: Set planting treatment The annual alternation single-season cropping system adopts grain and forage rotation treatment, with a single plot area of ​​35m² and a 1m isolation zone between plots; S3: Unified application of base fertilizer The uniform base fertilizer application rate for all communities is: N 120 kg·hm² -2 P2O5 90 kg·hm -2 K2O 90 kg·hm -2 The fertilizers selected are urea, superphosphate, and potassium sulfate; S4: Standardized sowing Every April, sowing is carried out uniformly. Three sets of crop rotation are matched with differentiated mulching, row and plant spacing, sowing depth and sowing amount are standardized and regulated. The uniform use of black mulch film with a width of 120cm and a thickness of 0.01mm is used for full film double furrow covering, with the large ridge 70cm and the small ridge 40cm, the ridge height 10-15cm, the film edge covered with 2-3cm of soil, and a horizontal soil pressing strip every 2m. S5: Layered Soil Sampling and Testing Two consecutive years of field experiments were conducted, with soil samples collected from two depths (0-20cm and 20-40cm) during the vigorous growth and maturity stages of the crop, respectively; the soil aggregate index R was measured. 0.25 WR 0.25 MWD, GMD, PAD, ELT, as well as soil pH, organic carbon, total nitrogen, and cation exchange capacity; S6: Grey relational comprehensive evaluation: integrating soil physical and chemical indicators for comprehensive scoring.

[0048] In this embodiment, the forage rotation in step S2 is a potato-oat (PO) rotation.

[0049] In this embodiment, the localized special varieties used in step S2 are: the potato is Dingshu No. 4 and the oat is Dingyan No. 2.

[0050] Example 2 The difference from Example 1 is that the forage rotation in step S2 is a corn-pea (MP) rotation, and the localized special varieties used in step S2 are: corn Dajingjiu 23 and pea Dingwan 10.

[0051] Example 3 The difference from Example 1 is that the crop rotation in step S2 is a wheat-alfalfa (WA) rotation, and the localized special varieties used in step S2 are: wheat Dingxi 40 and alfalfa Gannong 5.

[0052] Experimental Example 1 This experimental case is located in Xizhai Village, Xiangquan Town, Anding District, Dingxi City, Gansu Province (104°30'55.2"E, 35°27'37.9N). The climate of this area belongs to the North Temperate Semi-humid to Mid-Temperate Semi-arid zone, with obvious continental monsoon climate characteristics. The average annual temperature is between 5.7 and 7.7 ℃, the frost-free period is between 122 and 160 days, and the average annual rainfall is between 350 and 600 mm, but the rainfall distribution is uneven, mainly concentrated in July, August, and September. The average annual sunshine duration is between 2114 and 2433 hours. Before the experiment, the land use in this area was continuous cropping of maize, with the variety Gannong 3, and the growth condition was poor. At the start of the project, the original continuous cropping plots were uniformly prepared and divided into plots, and the initial soil conditions of each plot were consistent with the historical soil use. This study focuses on the cross-sectional comparative analysis of the results after the implementation of crop rotation. The local average temperature during this growing season was 22.5 ℃, and the cumulative precipitation was 220.2 mm. Detailed rainfall and temperature data for April-September 2024 and 2025 are shown in Table 1. The 2024 data are statistical values ​​for the entire Anding District, and the 2025 data are measured values ​​from the Anding District meteorological station. The soil type at the experimental site was mainly loess, with a texture of silty loam (85% silt, 31% sand, and 11% clay). The physicochemical properties of the topsoil before the experiment were: organic carbon 6.01 g·kg⁻¹. -1 pH 8.48, available nitrogen 45.23 mg·kg -1 16.4 mg·kg of readily available phosphorus -1 192.5 mg / kg of readily available potassium -1 .

[0053] Table 1. Changes in average temperature and cumulative precipitation in the experimental area from April to September, 2024-2025. 1. Experimental Design Field plot experiments were conducted, with both crops and forage grasses in the experimental plots operating on a single-crop-per-year system in a typical rainfed dryland farming area, and manual sowing in April each year. The experiment included five treatments: three crop rotation treatments (potato-oat (PO), forage maize-pea (MP), and wheat-alfalfa (WA), and two control treatments for continuous cropping of local typical crops (potato continuous cropping (CK1) and maize continuous cropping (CK2)). Each treatment was replicated three times, resulting in a total of 15 randomly arranged plots. The plot area was 35 m². 2 (5 m × 7 m), with a 1 m wide isolation strip between adjacent plots. Nitrogen, phosphorus, and potassium fertilizers are applied uniformly to the experimental plots before planting each year, at a rate of N = 120 kg·hm². -2 P2O5 90 kg·hm -2 K2O 90 kg·hm -2Nitrogen fertilizer is urea (containing 46% N), phosphorus fertilizer is superphosphate (containing 16% P2O5), and potassium fertilizer is potassium sulfate (containing 50% K2O). Planting in 2024 and 2025 will be done manually. See Table 2 for forage / crop varieties, sowing methods, and seed sources.

[0054] Table 2 Planting and sowing information for various forage crops in 2024 and 2025 2. Sample Collection and Processing Sampling was conducted in 2024 and 2025 during the peak growth and maturity stages of crops, respectively. The phenological periods corresponding to the peak growth and harvest stages of forage / crops are shown in Table 3, and the specific sample collection times are shown in Table 4. Soil samples were collected from each plot in the experimental area at depths of 0-20 cm and 20-40 cm using a 3.5 cm diameter soil auger. Five samples were collected from each soil layer in each plot and mixed to form one soil sample. Back in the laboratory, the soil samples were cleaned to remove gravel, plant roots, and other debris, preserving the original soil structure as much as possible. Soil clods were gently broken along natural fracture surfaces into pieces approximately 10 mm in diameter and placed in a well-ventilated, shaded area to air dry naturally. One portion of the dried soil was used for soil aggregate analysis, and the other portion was sieved through a 0.25 mm sieve for soil chemical property determination.

[0055] Table 3 Correspondence Table of Key Phenological Periods for Forage Grasses / Crops Table 4 Sample collection time 3. Measurement Indicators and Methods (1) Determination of soil aggregate composition and stability analysis Dry sieving and wet sieving methods are used to determine the composition and stability of soil aggregates. The specific operation of the dry sieving method is as follows: a set of sieves composed of 5 sieves with pore sizes of 5, 2, 1, 0.5 and 0.25 mm is placed on an automatic sieving instrument, 200 g of air-dried soil sample is placed on the uppermost sieve of the sieve set, shaken at a speed of 180 times per minute for 1 minute, the soil weights of 6 particle size fractions: >5 mm, 2-5 mm, 1-2 mm, 0.5-1 mm, 0.25-0.5 mm and <0.25 mm are collected and weighed respectively, and the proportion of mechanically stable soil aggregates with different particle sizes is calculated. Water-stable aggregates are determined by the wet sieving method, and the specific method is as follows: 50 g of air-dried soil sample is prepared according to the composition proportion of aggregates of each particle size obtained by the dry sieving method, the sieve set matched with the soil aggregate analyzer is placed into the water bucket of the aggregate analyzer from top to bottom (5, 2, 1, 0.5, 0.25 mm), water is added into the bucket until the position where the uppermost soil sample can be just wetted, the prepared 50 g soil sample is placed into the uppermost soil sieve, the switch is started after standing for 10 min, the sieve set vibrates up and down at a frequency of 30 times per minute for 5 min in the water bucket. After vibration is completed, the sieve set is carefully taken out of the water bucket, after draining for 3-5 min, the soil aggregates on each layer of soil sieve are washed into pre-numbered and weighed aluminum boxes with a washing bottle filled with distilled water, aggregates of 6 particle size fractions: >5 mm, 2-5 mm, 1-2 mm, 0.5-1 mm, 0.25-0.5 mm and <0.25 mm are collected, dried to constant weight, weighed and the proportion of water-stable aggregates with different particle sizes is calculated. Aggregate stability indicators include mean weight diameter of aggregates (MWD), geometric mean diameter (GMD), macroaggregate content (R 0.25 ), the amount of water-stable aggregates >0.25 mm (WR 0.25 ), percentage of aggregate disruption (PAD) and unstable aggregate index (ELT). Finally, the values of the above indicators are calculated. The specific calculation formulas are as follows: In the formula: R 0.25 represents the content of mechanically stable aggregates >0.25 mm (%); WR 0.25M<0.25 indicates the content of water-stable aggregates with a particle size of >0.25 mm (%); M<0.25 indicates the total weight (g) of soil aggregates with a particle size of less than 0.25 mm; MT indicates the total weight (g) of soil before sieving; M indicates the weight (g) of soil aggregates with a particle size of >0.25 mm before water sieving. Wi represents the average diameter (mm) of the i-th particle size aggregate; Wi represents the percentage of the i-th particle size aggregate content (%); WT represents the total mass (g) of soil required for water sieving.

[0056] (2) Determination of soil chemical properties Soil pH determination: potentiometric method; Soil organic carbon content determination: potassium dichromate external heating method; Soil cation exchange capacity determination: hexaamminecobalt trichloride extraction-spectrophotometric method; Soil total nitrogen content determination: Kjeldahl method.

[0057] 4. Test Results (1) Effects of different crop rotation patterns on soil aggregate composition and distribution (1.1) Composition and distribution of soil mechanical stability aggregates In 2024, during the vigorous growth period, the 0-20 cm soil layer ( Figure 1 The particle size distribution of aggregates under each treatment showed that large aggregates (>0.25 mm) dominated, while micro-aggregates (<0.25 mm) had a lower proportion. In the vigorous growth stage (20-40 cm soil layer), compared to the 0-20 cm layer, the proportion of large particles increased by 5-10% overall. Particle sizes of 0.5-0.25 mm and <0.25 mm decreased compared to the 0-20 cm soil layer, while other particle sizes increased. In the mature stage (0-20 cm soil layer), compared to the vigorous growth stage, the proportion of >0.25 mm particles increased in all treatments, but the <0.25 mm particle size showed a rapid increase in the MP and WA treatments. The PO treatment showed a stable increase in the content of >0.25 mm aggregates compared to the vigorous growth stage, with more significant changes in CK1 and CK2 compared to the crop rotation treatment, and a significant decrease in the content of <0.25 mm aggregates. In the mature 20-40 cm soil layer, the proportion of large-sized particles further increased in all treatments, and the changes in <0.25 mm particle size in MP and WA were consistent with those in the 0-20 cm layer. Overall, from vigorous growth to maturity, the proportion of large-sized particles in the 0-20 cm soil layer increased by an average of 10%, and in the 20-40 cm layer by 5-15%; the proportion of large-sized particles in the 0-20 cm layer was lower than that in the 20-40 cm layer, by an average of 10-20%.

[0058] 2025 ( Figure 2During the vigorous growth stage, in the 0-20 cm soil layer, the PO treatment had the lowest content of particles >5 mm and the MP treatment had the highest content. In the 20-40 cm soil layer, the MP treatment had a significantly higher content of aggregates >5 mm than other treatments, while the 1-0.5 mm particle size had the lowest content among all treatments. In the mature stage (0-20 cm soil layer), compared to the vigorous growth stage, the proportion of large particles increased by about 5-10% in all treatments, with the largest increases in >5 mm and 1-0.5 mm particles. In the 20-40 cm soil layer, the proportion of 5-2 mm particles further increased by about 5% compared to the 0-20 cm soil layer, while the 1-0.5 mm particle size further decreased, and the 0.5-0.25 mm and <0.25 mm particle sizes showed a trade-off. Soil structure degradation was more pronounced during the vigorous growth stage, while the soil structure became more stable during the mature stage.

[0059] Comparing 2024 and 2025, the total proportion of large-sized particles (>5 mm and 5-2 mm) was on average 5-10% higher in 2025, especially in the vigorous growth stage (0-20 cm) of the MP rotation pattern. Medium-sized particles (2-1 mm and 1-0.5 mm) dominated the WA treatment in 2024, maintaining a stable proportion of 40-55%. Growth stage changes showed that, from vigorous growth to maturity, the increasing trend of large-sized particle proportions was consistent in both years, except for the mature MP and WA treatments in 2024, with a greater increase in the 0-20 cm soil layer than in the 20-40 cm layer. In the rotation treatments, the MP and WA treatments had a higher proportion of >0.25 mm particles compared to continuous cropping, averaging 10-20% higher, and the distribution of 5-2 mm and 2-1 mm particles was more balanced.

[0060] (1.2) Composition and distribution of soil water-stable aggregates Depend on Figure 3 and Figure 4 It can be seen that the aggregate particle size in both years was mainly <0.25 mm. (2024) Figure 3 During the vigorous growth period in the 0-20 cm soil layer, the proportion of aggregates <0.25 mm exceeded 60% in all treatments, with the MP treatment having the lowest proportion. The MP treatment had the highest content among particles with diameters of 0.5-0.25 mm and 1-0.5 mm. The distribution was similar at a depth of 20-40 cm. At the mature stage in the 0-20 cm depth, the proportion of particles <0.25 mm was similar to that during the vigorous growth period, remaining dominant, but some MP treatments showed a greater distribution of medium-sized particles. At a depth of 20-40 cm, the crop rotation treatment showed a lower content of aggregates >0.25 mm compared to the continuous cropping treatment.

[0061] 2025 ( Figure 4During the vigorous growth stage (0-20 cm), the proportion of aggregates <0.25 mm was higher than 80% in all treatments, while the proportion of aggregates >5 mm was the lowest. The PO and MP treatments had higher proportions of aggregates >0.25 mm than other treatments, while the WA treatment had the lowest content of aggregates >0.25 mm. Below the 20-40 cm soil layer, the proportion of aggregates <0.25 mm decreased slightly, while the proportion of aggregates 0.5-0.25 mm increased, especially in the CK1, PO, and MP treatments, with a slight decrease in the CK2 treatment. The changes in aggregate size during the mature stage were similar to those during the vigorous growth stage. Below the 0-20 cm soil layer, aggregates with a size of 5-2 mm increased. In the 20-40 cm layer, the PO treatment showed more stratification in the distribution of 1-0.5 mm and 0.5-0.25 mm aggregates compared to the 0-20 cm layer. In summary, the PO treatment has a certain effect on improving the water stability of soil aggregates.

[0062] Compared to 2024, in 2025, during the vigorous growth stage (0-20 cm depth), the proportion of large aggregates (>2 mm) was similar across all treatments, while microaggregates (<0.25 mm) accounted for over 80%. However, the proportion of particles with a diameter of 0.5-2 mm decreased slightly in 2025, especially in the PO and MP treatments. At a depth of 20-40 cm, the proportion of aggregates with a diameter <0.25 mm decreased slightly in 2025 compared to 2024, while the proportion of large aggregates increased accordingly, particularly in the PO treatment, which showed a greater variety of particle sizes. During the mature growth stage (0-20 cm depth), the proportion of small aggregates was similar to that of 2024 in 2025, but aggregates with a diameter >5 mm were more abundant in 2025, as seen in the PO and MP treatments. At a depth of 20-40 cm, the overall distribution in 2025 was more stratified than in 2024, with a decrease in the proportion of <0.25 mm aggregates and an expansion of the middle layer particle size in all treatments, especially in the CK1 and PO treatments where the bottom layer was more abundant.

[0063] (2) Effects of different crop rotation patterns on soil aggregate stability (2.1) Soil mechanical aggregates (R 0.25 ) and water-stable aggregates (WR) 0.25 )content like Figure 5 As shown, different crop rotation patterns significantly affected the soil's >0.25 mm mechanical stability aggregates (R0.25). 0.25 ) and water-stable aggregates (WR) 0.25 The content of ) P <0.05). During the vigorous growth period of the 0-20 cm soil layer in 2024, the content of large aggregates (R) among the CK1, PO, and MP treatments... 0.25 No significant difference was observed in CK2 levels, but CK2 was significantly higher than in the WA treatment; at maturity, CK2 was significantly higher than in other treatments, while MP treatment showed higher R levels.0.25 The content was the lowest. In the 20-40 cm soil layer, the CK1, CK2, and PO treatments were still higher than the MP and WA treatments. Entering 2025, the MP treatment showed higher R content during the vigorous growth period in both the 0-20 cm and 20-40 cm soil layers. 0.25 Value, conversely, PO processing R 0.25 The content was slightly lower than in 2024. It is worth noting that during the vigorous growth period in the 20-40 cm soil layer, the R content of the WA treatment was [missing information]. 0.25 The value was significantly lower than other treatments.

[0064] In water-stable aggregates (WR) 0.25 Regarding the treatment of PO and MP, both treatments significantly increased the content of water-stable macroaggregates in the soil, but the improvement effects of the two treatments showed significant differences in soil stratification. 0-20 cm topsoil: PO treatment with WR during the vigorous growth and maturity stages in 2024. 0.25 The highest content was found in WR, approaching 40%, significantly higher than MP, WA, and the two continuous cropping controls; during the vigorous growth and maturity stages in 2025, the surface layer was transformed into MP-treated WR. 0.25 The highest content is found in PO, followed by PO. 20-40 cm deep soil: In both experimental years, the MP treatment showed WR 0.25 The improvement effect was better than that of PO treatment, but the improvement of deep water-stabilized aggregates in PO was significantly weaker than that in the surface layer; data from both years showed that WA treatment improved WR in the 20-40 cm soil layer. 0.25 The content was the lowest, below 5% in some periods, significantly lower than PO, MP and the continuous cropping controls CK1 and CK2.

[0065] The combined results of the two-year stratification show that PO has a significant advantage in improving water-stable aggregates in the top 0-20 cm soil layer, while MP has a stronger long-term effect on improving water-stable aggregates in the 20-40 cm deep soil layer.

[0066] (2.2) Mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates Different crop rotation patterns ( Figure 6 This significantly affected the mean weight diameter and geometric mean diameter of soil aggregates. P<0.05). Regarding MWD, significant differences existed among treatments in both 2024 and 2025. In 2024, during the vigorous growth period, the MWD value of the MP treatment in the 0-20 cm soil layer was significantly higher than that of the CK2 and WA treatments, but in the mature stage, CK2 was significantly higher than other treatments. In the 20-40 cm soil layer, CK1 was significantly higher than other treatments, with the MP treatment showing the lowest value during the vigorous growth period, and the WA treatment significantly lower than other treatments in the mature stage. In 2025, the MP treatment performed best during the vigorous growth period and worst during the mature stage. In the 20-40 cm deep soil layer, the MP treatment showed similar variation across different periods as the 0-20 cm layer, while the WA treatment consistently maintained a low MWD value. The trends in geometric mean diameter were generally consistent with the MWD trends.

[0067] (2.3) Soil aggregate disruption rate (PAD) and unstable aggregate index (ELT) like Figure 7 As shown, different crop rotation patterns significantly affected the soil aggregate disruption rate and unstable aggregate index (SCI). P <0.05), and significant annual and soil layer differences were observed among the treatments. In 2024, the differences in aggregate destruction rates among the treatments were relatively small, with values ​​mainly ranging from 60% to 85%. The MP treatment showed significantly lower rates than other treatments in all soil layers at all times. In 2025, the differentiation among treatments intensified. The WA treatment showed significantly higher destruction rates in both soil layers, especially in the mature stage, where its destruction rate approached or exceeded 90%, significantly higher than other treatments. In contrast, the PO treatment maintained a lower destruction rate in 2025. The trend of the unstable aggregate index was basically consistent with the destruction rate. In 2025, the instability index of the WA treatment increased sharply, especially in the mature 20-40 cm soil layer, where its index approached 100%, significantly higher than all other treatments. Meanwhile, the instability index of the PO treatment was significantly lower than that of the WA treatment. Overall, the aggregate destruction rate and unstable aggregate index slightly increased in 2025 compared to 2024.

[0068] In summary, crop rotation patterns (especially PO and MP) can effectively reduce the destruction rate and instability index of soil aggregates, and enhance the stability of soil structure; while WA treatment significantly increases the instability of aggregates, which is detrimental to improving soil stability in the Loess Plateau region. This result is consistent with the analysis results of MWD and GMD mentioned above.

[0069] Furthermore, it cannot be generally concluded that PO and MP have the same effect on improving water-stable aggregates, as their advantages in improving soil layers differ: potato-oat (PO) rotation is more conducive to the stability of soil aggregate structure in the topsoil layer, while corn-pea (MP) rotation for feed has a more significant advantage in improving water-stable aggregates in the deep sub-topsoil layer.

[0070] (3) The effects of different crop rotation patterns on key soil chemical properties (3.1) Soil pH like Figure 8 As shown, different crop rotation patterns significantly affected soil pH ( P <0.05), and significant annual and soil layer differences were observed among the treatments. Soil pH generally showed a decreasing trend in 2024 and 2025. In 2024, the pH range for each treatment was 8.2-8.5, while in 2025 it decreased to 8.1-8.4. In both years, the pH of the MP treatment was generally lower than that of the PO and WA treatments. In the 0-20 cm soil layer during the vigorous growth period in 2024, the pH of the MP treatment was 8.25, significantly lower than the 8.40 of the CK1 treatment (<0.05). P <0.05); This difference will be even more pronounced in 2025, with the pH value of MP treatment dropping to around 8.20, while CK1 will remain above 8.30.

[0071] (3.2) Soil total nitrogen content There were significant differences in soil total nitrogen content among treatments in 2024 and 2025. Figure 9 In 2024, the total nitrogen content in the 0-20 cm soil layer was relatively high in the PO and MP treatments, and also higher than in the 20-40 cm soil layer, reaching 0.83 and 0.91 g / kg respectively during the vigorous growth period, significantly higher than CK1 (0.56 g / kg) and WA (0.60 g / kg). By 2025, the total nitrogen content in the MP treatment significantly increased, reaching approximately 1.40 g / kg at maturity, significantly higher than all other treatments; while the PO and WA treatments remained at the 0.90-1.00 g / kg level. In the 20-40 cm deep soil layer, the total nitrogen content was generally lower than in the 0-20 cm surface soil layer. In 2024, the total nitrogen content of each treatment ranged from 0.50 to 0.75 g / kg, with the PO and MP treatments maintaining a relative advantage. In 2025, the crop rotation treatment also showed a significant increase in total nitrogen content across all periods, reaching approximately 0.90 g / kg, significantly higher than CK1 and CK2 treatments (approximately 0.50-0.55 g / kg). This indicates that crop rotation, especially the MP pattern, can effectively increase the total nitrogen content of the soil, and this effect is more pronounced in the second year.

[0072] (3.3) Soil organic carbon content From 2024 to 2025, the soil organic carbon content in all treatments generally showed an upward trend. Figure 10The organic carbon content of each treatment ranged from 6.23 to 7.91 g / kg in 2024, increasing to 6.93 to 8.97 g / kg in 2025. The organic carbon content in the 0-20 cm soil layer was generally higher than that in the 20-40 cm deeper soil layer. In 2024, the average organic carbon content in the 0-20 cm soil layer was 7.4 g / kg, while it was 6.8 g / kg in the 20-40 cm soil layer; in 2025, these figures increased to 8.5 g / kg and 7.8 g / kg, respectively. Among different crop rotation patterns, the organic carbon content of the PO and MP treatments was generally higher. In 2025, during the vigorous growth period of the 0-20 cm soil layer, the organic carbon content of the PO treatment reached approximately 9.0 g / kg, significantly higher than other treatments. P <0.05). Treatments CK1 and CK2 showed moderate performance, with organic carbon content remaining at 8.0-8.5 g / kg. Although treatment WA showed improvement in 2025, it remained lower than treatments PO and MP at all times.

[0073] (3.4) Soil cation exchange capacity From 2024 to 2025, the soil cation exchange capacity (CEC) of all treatments generally showed an upward trend. In 2024, the CEC ranged from 9.2 to 11.5 cmol / kg, while in 2025 it increased to 9.8 to 12.3 cmol / kg. The CEC in the 0-20 cm topsoil layer was generally higher than that in the 20-40 cm deep soil layer. In 2024, the mean CEC in the 0-20 cm soil layer was 10.5 cmol / kg, while it was 10.0 cmol / kg in the 20-40 cm soil layer; in 2025, these values ​​increased to 11.4 cmol / kg and 10.7 cmol / kg, respectively. Among the five planting patterns, the CEC of the PO and MP treatments was generally higher. In 2025, during the vigorous growth period in the 0-20 cm soil layer, the CEC of the MP treatment reached approximately 12.3 cmol / kg, significantly higher than that of the CK1 treatment. P <0.05), and PO treatment also reached above 11.5 cmol / kg. CK1 treatment remained at a low level in both years, with CEC values ​​between 9.5 and 10.8 cmol / kg. CK2 and WA treatments showed moderate performance, with CEC values ​​between 10.0 and 11.8 cmol / kg. In conclusion, crop rotation can significantly improve soil cation exchange capacity, with the MP model showing the best effect, and this effect is more pronounced in the topsoil and in the second year of rotation. Figure 11 ).

[0074] (4) Comprehensive ranking of grey relational degree As shown in Table 5, the soil layer ranking during the vigorous growth period in 2025 was: MP > WA > PO > CK2 > CK1, and during the 20-40 cm soil layer, the ranking was: MP > PO > CK2 > CK1 > WA. During the mature growth period, the ranking was: MP > WA > PO > CK1 > CK2, and during the 20-40 cm soil layer, the ranking was: MP > PO > WA > CK2 > CK1. Overall, the MP treatment was the dominant treatment in all soil layers at all stages, followed by the PO treatment, and its performance trend was relatively stable across stages. In contrast, the WA treatment performed the worst among the three crop rotation treatments, especially showing a significant difference between the 0-20 cm and 20-40 cm soil layers during the vigorous growth period.

[0075] Table 5. Grey Relational Degree of All Indicators in All Periods under Different Crop Rotation Patterns in 2025 In summary, the forage-maize-pea (MP) rotation pattern significantly increased the content of large and water-stable aggregates in the soil of the Loess Plateau dryland region, increased the mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates, decreased the soil aggregate destruction rate (PAD) and unstable aggregate index (ELT), and lowered soil pH. It also increased the content of total nitrogen, organic carbon, and cation exchange capacity (CEC) in the soil, thereby improving soil nutrient storage capacity and fertilizer retention. Therefore, the forage-maize-pea rotation pattern is an effective way to improve soil aggregate stability and fertility in the Loess Plateau dryland region, and can synergistically enhance soil structural stability and ecological function.

[0076] Based on the combined results of two years of stratified soil indices and grey relational ranking, it can be concluded that: MP is the optimal crop rotation for comprehensive soil improvement and fertilization; PO has a moderate improvement effect; WA has significant shortcomings in soil improvement, with insufficient stability of deep soil aggregates and nutrient enhancement capacity, and is only recommended for plots with long-term forage production needs and low requirements for farmland improvement.

[0077] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0078] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for crop rotation and soil improvement in the dryland areas of the Loess Plateau, characterized in that, Includes the following steps: S1: Site Selection A plot of land in the dryland loess soil of Dingxi Loess Plateau, Gansu Province, where maize is continuously cropped, was selected and the land was uniformly prepared and divided into experimental plots. S2: Set planting treatment The plantation adopts a single-crop-per-year rain-fed cultivation method and a grain-forage rotation treatment. The area of ​​a single plot is 35m², and a 1m isolation strip is set between plots. S3: Unified application of base fertilizer The uniform base fertilizer application rate for all communities is: N 120 kg·hm² -2 P2O5 90 kg·hm -2 K2O 90 kg·hm -2 The fertilizers selected are urea, superphosphate, and potassium sulfate; S4: Standardized sowing Sowing is carried out uniformly every April, with supporting measures such as ridging and mulching, standardized row spacing and plant spacing for spot sowing / row sowing. S5: Layered Soil Sampling and Testing Soil samples were collected from two layers (0-20cm and 20-40cm) during the vigorous growth and maturity stages of the crop, respectively; the soil aggregate index R was measured. 0.25 WR 0.25 MWD, GMD, PAD, ELT, as well as soil pH, organic carbon, total nitrogen, and cation exchange capacity; S6: Grey relational comprehensive evaluation: integrating soil physical and chemical indicators for comprehensive scoring.

2. The method for crop rotation and soil improvement in the dryland area of ​​the Loess Plateau as described in claim 1, characterized in that, The forage rotation in step S2 is a potato-oat rotation, a forage corn-pea rotation, or a wheat-alfalfa rotation.

3. The method for crop rotation and soil improvement in the dryland area of ​​the Loess Plateau as described in claim 2, characterized in that, The following localized special varieties are used in step S2: Dingshu No. 4 potato, Dajingjiu 23 for feed corn, Dingxi 40 wheat, Dingyan No. 2 oats, Dingwan No. 10 peas, and Gannong No. 5 alfalfa.

4. The method for crop rotation and soil improvement in the dryland area of ​​the Loess Plateau as described in claim 3, characterized in that, The potato-oat rotation is as follows: In the first year, potatoes "Dingshu No. 4" are planted on 20cm high ridges covered with 1m black plastic film, with spot sowing, row spacing of 25cm, plant spacing of 30cm, sowing depth of 10-12cm, and sowing rate of 275kg / hm²; in the second year, oats "Dingyan No. 2" are sown in open fields with a row spacing of 20cm, sowing depth of 3-4cm, and sowing rate of 75kg / hm².

5. The method for crop rotation and soil improvement in the dryland area of ​​the Loess Plateau as described in claim 4, characterized in that, The specific crop rotation of feed corn and peas is as follows: In the current year, feed corn "Dajingjiu 23" is sown individually under a 1m white film, with a row spacing of 40cm, a plant spacing of 15cm, a sowing depth of 4-5cm, and a sowing rate of 30kg / hm²; in the following year, peas "Dingwan 10" are sown in rows with a 20cm row spacing, a sowing depth of 3cm, and a sowing rate of 105kg / hm².

6. The method for crop rotation and soil improvement in the dryland area of ​​the Loess Plateau as described in claim 5, characterized in that, The wheat-alfalfa rotation is as follows: in the first year, wheat "Dingxi 40" is sown in rows with a spacing of 20cm, a sowing depth of 3-4cm, and a sowing rate of 180kg / hm²; in the second year, alfalfa "Ganong 5" is sown in rows with a spacing of 20cm, a sowing depth of 1-1.5cm, and a sowing rate of 12kg / hm².

7. A method for crop rotation and soil improvement in the dryland area of ​​the Loess Plateau as described in any one of claims 4-5, characterized in that, After all crops are sown, compact the soil promptly. Make drainage holes every 50cm in the furrows. When seedlings emerge, promptly break the film to release the seedlings and seal the film holes with fine soil to retain moisture.

8. The method for crop rotation and soil improvement in the dryland area of ​​the Loess Plateau as described in claim 1, characterized in that, Step S2 adopts a corn-pea rotation pattern for feed.

9. The method for crop rotation and soil improvement in the dryland area of ​​the Loess Plateau as described in claim 1, characterized in that, In step S5, the soil aggregates were determined by dry sieving to determine mechanically stable aggregates and by wet sieving to determine water-stable aggregates.

10. A method for crop rotation and soil improvement in the dryland areas of the Loess Plateau as described in claim 1, characterized in that, The method is applicable to rain-fed dryland farmland in Huangmian soil, Dingxi, Gansu Province, with an average annual rainfall of 350-600 mm and an average annual temperature of 5.7-7.7℃.

Images