Field Crop 2025, Vol.8, No.4, 187-194 http://cropscipublisher.com/index.php/fc 189 3 Mechanisms Enhancing Water Use Efficiency 3.1 Improved soil moisture retention through surface residue cover In many fields, people have found that as long as the crop residues after harvest are left on the surface, the moisture condition of the soil can be improved significantly. This is particularly evident in no-till or cover tillage. Straw acts like a barrier. First, it blocks the direct evaporation of water, and then it helps rainwater or irrigation water seep in more easily. Compared with traditional ploughing, the soil moisture content under residue cover is often 8-33% higher, and this difference is more obvious during the critical growth period of crops (Du et al., 2023). 3.2 Reduced evaporation and enhanced infiltration rates Conservation tillage reduces soil tillage and can maintain its original structure and porosity by itself. In addition, with the stubble covering, the surface temperature fluctuates little, the wind speed is suppressed, and the evaporation is correspondingly reduced. More importantly, the surface layer of the soil is less likely to form a crust, its aggregation is enhanced, and both the speed and depth of water infiltration increase. In this way, the root zone can acquire more water reserves. Especially in semi-arid or even arid areas, this advantage often determines whether crops can smoothly pass through the growing season (Su et al., 2007; Cong et al., 2024). 3.3 Influence on root development and water uptake efficiency Once soil conditions improve, the growth pattern of plant roots will also change accordingly. They tend to grow deeper and be more widely distributed, expanding their range of water acquisition and naturally having stronger drought resistance. At the same time, the physiological state of the plants will also be better as a result, such as higher water potential in the roots and leaves, more dry matter accumulation, and more prominent stress resistance. Taken together, these factors have driven the improvement of water use efficiency (WUE) and ultimately supported the yield (Peng et al., 2019; Peng et al., 2020). 4 Agronomic and Environmental Benefits of Conservation Tillage 4.1 Yield stability and resilience under drought-prone conditions The effect of conservation tillage is most easily observed in areas where rainfall is unstable or drought is prone to occur. No-tillage and less tillage methods often make the yield more stable, and sometimes even increase it. With the improvement of soil structure, water can be retained better and evaporation is less, so crops are naturally less likely to be crushed by water shortage. Many studies and meta-analyses have reached similar conclusions: in semi-arid and arid regions, production can increase by approximately 5-10%, especially during water shortages (Qin et al., 2024). As for the improvement in resilience, it is mostly attributed to the enhancement of water supply and root development. When these two factors are combined, the yield does not fluctuate greatly with different seasons (Deng et al., 2022). 4.2 Reduction in runoff and erosion The problem of soil erosion is actually very common in farmlands. One notable benefit of conservation tillage is to suppress this matter. The surface stubble remains, and the soil is less affected by raindrops and wind, so the runoff is naturally reduced. Compared with traditional farming methods, the soil loss rate has decreased significantly. This not only retains fertility but also reduces the amount of sediment and chemical substances flowing into rivers and lakes, thereby improving water quality (Busari et al., 2015). In the long run, erosion prevention is about maintaining soil productivity and delaying land degradation. 4.3 Enhanced soil organic matter and carbon sequestration Over time, the effects of conservation tillage on organic matter and carbon will become apparent. Because the decomposition rate of stubble has slowed down, they are more likely to accumulate in the soil, thereby increasing soil organic matter (SOM). Many studies have pointed out that measures such as no-tillage and straw mulching can significantly increase the organic carbon in the surface soil while reducing greenhouse gas emissions (Hussain et al., 2021; Wang et al., 2022). These changes bring many benefits: smoother nutrient cycling, enhanced soil fertility, and the ability to "lock" more carbon in farmland, which can be regarded as an indirect contribution to mitigating climate change (Wang et al., 2021).
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