Legume Genomics and Genetics 2025, Vol.16, No.6, 288-296 http://cropscipublisher.com/index.php/lgg 290 3 Effects of Film Mulching on Broad Bean Germination 3.1 Enhanced germination rates due to stable soil temperatures In the first few days after sowing the seeds, whether the surface temperature can be stable is actually quite critical. Can the mulch help? Experimental data shows that it can. New mulch can increase the surface temperature by 18.4%, and old mulch can also increase it by 11.4% (Zhao et al., 2022). It doesn't sound like much, but in cold weather or at the beginning of spring, this temperature difference may be the "watershed" that determines whether or not the seeds will germinate. However, the hotter the better, and local overheating may damage the roots. Therefore, the temperature increase should be just right, which will help germination without being "suffocated". 3.2 Reduction in seedling mortality by maintaining adequate soil moisture The difference between covering with film and not covering with film can be seen quickly. After a few days of exposure to the sun, the water evaporates quickly, and the seedlings fall to the ground without absorbing any water. The film acts like a blanket covering the soil, which reduces water evaporation and makes the area around the roots more moist. According to data, the water content of covered soil is about 11% higher than that of uncovered soil (Jasim & Alghrebawi, 2020). This amount of water is particularly critical in the seedling stage, not only for survival, but also for rapid growth and nutrient absorption. 3.3 Influence of mulch color and transparency on germination efficiency Film is not just about covering it. Different colors and transparency are really important. Some people used semi-transparent film and found that broad beans grew better than before. It is not a coincidence. The main reason is that this film allows sunlight to penetrate while preventing the surface from getting too hot, which is a good balance (Yuan et al., 2010). Although there are not many comparative studies on different colors, from experience, semi-transparent and ordinary plastic films have significantly improved germination rates and early growth. So when choosing a film, you really can't just look at whether it is cheap or not. You also have to look at the weather and soil quality. Whether it is suitable is the key. 4 Impact on Soil Moisture Conservation 4.1 Prolonged retention of soil water content in root zones After laying a film (whether plastic or biodegradable), evaporation will be much less, and the soil's water storage capacity will be stronger, so the root zone is wetter, and the upper layer of 0-20 cm is most obvious (Chen et al., 2019). The experiment found that the moisture content of the plots covered with white film was higher than that of bare land in the soil layer up to 10 meters deep, which can retain water longer and extend the water supply time of crops (Wang et al., 2022). This effect is most prominent in the early and middle stages of crop growth, which can ensure that broad bean roots always have water to absorb (Li et al., 2022). 4.2 Reduced frequency of irrigation and water input Because water is not easy to escape, there is no need to water frequently after laying the film. Studies have shown that fields with film use less water, and some treatments save up to 41.86% of water compared to those without film (El-Shafie et al., 2024). In addition, the film can also reduce soil evaporation and evapotranspiration by 60.7% and 10.1% respectively, further saving water, while maintaining or even improving yield and water use efficiency. 4.3 Prevention of soil crusting and enhancement of soil structure The ground film can also block direct rainwater erosion and reduce strong evaporation, so the soil surface is not easy to form lumps, not easy to be compacted, and water can seep in more easily. Under the conditions of film laying, infiltration is enhanced, soil structure is improved, and the dry soil layer recovers faster; among them, the white film has the most outstanding rain storage efficiency and water recovery effect. After the structure becomes loose, the roots are easier to stretch and the soil is healthier (Mao et al., 2020). 5 Influence on Plant Growth and Yield 5.1 Improvement in early plant vigor and root development Mulching can increase soil temperature and make humidity more stable, which helps plants grow more vigorously
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