Molecular Soil Biology 2025, Vol.16, No.5, 272-286 http://bioscipublisher.com/index.php/msb 281 reduce the risk of waterlogging and yield reduction. Ridge cultivation can be considered to increase the bed height, which is also conducive to drainage and warming. Combining the above measures, a multi-pronged management approach such as drainage, deep plowing, crop rotation and selection of tolerant varieties can be adopted for heavy clay soils, which can significantly improve the growth environment of bean crops, reduce the occurrence of root rot and seedling death, and ensure yield formation. 6.3 Water retention and mulching technology in light sandy soil environment Light loam and sandy soil are prone to drought stress due to their poor water retention capacity, which is a key problem to be overcome in bean cultivation. On this type of soil, the cultivation technology of "water retention and moisture increase" should be emphasized, including mulching to retain moisture, zoned irrigation and soil fertilization. Mulching technology has been widely used in crops such as peanuts and mung beans in northern dry farming areas. By covering with plastic film, soil moisture evaporation is reduced and the water use efficiency of crops is significantly improved. Studies have shown that planting mung beans with mulching on semi-arid sandy land can increase soil water storage by more than 20% during the growing period compared with no mulching, and increase yield by 15% to 25% (Wang et al., 2022). Mulch can also increase soil temperature, accelerate the growth of bean seedlings, and have a certain weed suppression effect. However, long-term use of mulch can also cause residual film pollution problems, which require measures such as residual film recycling. In addition to mulch, organic mulching is also an effective moisture conservation measure. For example, spreading straw and rice straw on mung bean fields can cool and retain moisture and reduce surface runoff. Chalise et al. (2019) found that covering crop residues can increase soil water content from 0 cm to 10 cm, reduce soil temperature and improve the yield structure of soybean populations. In areas where water resources permit, the "small water frequent irrigation" method can be used to make up for the defect of sandy soil that is easy to lose water. The application of drip irrigation or micro-sprinkler irrigation in sandy peanuts shows that segmented and multiple irrigation saves more than 50% of water than traditional flooding, while increasing the number of crop pods and 100-grain weight. Therefore, it is advisable to promote water-saving irrigation technology on light sandy soil to improve water use efficiency. On the other hand, in view of the problem of easy loss of nutrients in sandy soil, it is necessary to pay attention to increasing the application of organic fertilizers and planting green manures to improve soil fertility and gradually improve soil texture and structure. Through continuous fertilization for several years, the organic matter and clay content of sandy soil can be significantly increased, thereby enhancing the soil's ability to retain water and fertilizer (Chalise et al., 2019). For example, in an experiment in the Northwest Irrigation Area, 5 tons/hectare of organic fertilizer was added to the mung bean field for three consecutive years, and the organic matter content of sandy loam increased by 0.3 percentage points, the field water holding capacity increased by 2 percentage points accordingly, and the average yield of mung beans increased by 12% compared with the control. On light sandy soil, a three-pronged approach of "covering + water conservation + fertilization" is needed: covering to retain moisture is a temporary solution, improving soil quality is a fundamental solution, and reasonable irrigation can ensure that legumes can grow normally and obtain higher yields in a dry and leaky soil environment. 7 Analysis of Typical Application Cases in Different Ecological Zones 7.1 Northeast black soil region: combination of high-yield soybean cultivation and straw return to the field The soil in the black soil region of Northeast China is fertile, but long-term cultivation has caused problems such as organic matter decline and soil erosion. In order to ensure the continued high yield of soybeans, the local area has explored a technical system of "high-yield cultivation mode + straw return to the field". On the one hand, by breeding soybean varieties that are resistant to dense planting and lodging, and supporting dense planting and fine management, a breakthrough in yield is achieved; on the other hand, the straw of crops such as corn is crushed and returned to the field, fertilizing the soil and improving the soil structure year by year. Taking the high-yield research field in Hailun City, Heilongjiang Province as an example, high-yield varieties are selected with dense planting of 250 000 plants per hectare, and the soybean yield exceeds 4 tons/hectare. At the same time, the full amount of straw is returned to the field and the no-till mulching technology is implemented. The organic matter content of black soil has increased from 3.5% to more than 4% within 5 years, and the soil's ability to store water
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