Bioscience Methods 2025, Vol.16, No.5, 254-261 http://bioscipublisher.com/index.php/bm 255 soil (Zamora Natera et al., 2022). Yellow lupine is particularly stable. No matter how the environment changes, it can grow well. It is a very promising green manure crop. 2.2 Nitrogen fixation and organic matter contribution The most famous point of leguminous green manure is that it can "grab" nitrogen in the air and help the soil add nutrients. Their nitrogen fixation is related to the species and environment. Some species do not fix nitrogen when the soil is too poor, but broad beans can fix up to 419 kg of nitrogen per hectare, and yellow lupins can fix more than 200 kg (Aguiar et al., 2024). After green manure is applied to the field, the nitrogen content of the soil can increase by up to 200 kg/hectare. This can help us use less chemical fertilizers and make the next crop grow better. These green manures can also bring a lot of organic matter, improve soil structure, and make the soil more fertile (Lyu et al., 2024). 2.3 Decomposition rate and release of major mineral elements After green manure is applied to the field, it will slowly decompose and release nutrients. The speed of its decomposition mainly depends on what kind of plant it is, when it is returned to the field, and what the climate is like. Some green manures, such as lupins and Indian Viola yedoensis, can release 60% to 80% of nitrogen 4 to 6 weeks after returning to the field (Herath et al., 2023). Sword beans and dwarf beans decompose very quickly and are suitable for short-term nutrient supplementation; but dodder and pigeon pea decompose more slowly and are more suitable for long-term soil covering and moisture retention (Mangaravite et al., 2023). Generally speaking, green manure decomposes quickly at first and then slows down, so that nutrients can be provided quickly and then continuously supplemented later. The minerals such as nitrogen, phosphorus, and potassium released by green manure are closely related to the decomposition speed, and the decomposition speed is also affected by what it contains, such as the ratio of lignin to nitrogen (Silva et al., 2008; Watthier et al., 2020). 3 Rotation Design and Field Management 3.1 Sowing, incorporation timing, and tillage practices In legume rotation, the planting and use of green manure should be planned in advance. Leguminous green manures such as broad beans, peas, vetch and lupins are usually planted at the beginning of the rotation. Compost and phosphate rock are usually spread before land preparation, which allows crops to better absorb nutrients (Meena et al., 2018). Green manure is usually returned to the field when the grain is about halfway into the grain filling or when it grows more lushly, which can maximize the nitrogen fixation effect and organic matter (Toleikienė et al., 2024). Tillage methods can be plowing or less tillage (such as chiseling), both methods are effective. However, the choice of which method should be considered in the long run, such as whether soil nutrients will be lost, especially when used with other organic fertilizers (Diacono et al., 2019). Compared with returning fresh green manure directly to the field, fermented or composted green manure, such as clover, can help release nitrogen more evenly and reduce nutrient loss. 3.2 Rotation cycle and legume cultivar matching How to arrange the crop rotation and what legume green manure to use are the two things that determine whether the green manure is effective. Green manure is often rotated with grain crops or vegetables, such as corn, wheat, barley, onions, etc., which can increase the yield and nutrient cycle in the field (Gao et al., 2024; Nguyen et al., 2024). When choosing green manure, you should consider the local climate and what the next crop needs. For example, broad beans and wild peas have good water retention and strong nitrogen fixation, while narrow-leaved lupines and peas are more outstanding in absorbing phosphorus (Céspedes et al., 2022). The amount of green manure returned to the field (generally 2 000 to 4 000 kg dry weight per hectare) and the time of returning the green manure to the field will affect the nutrient and yield changes in the field. If there is more rainfall and the climate is suitable, the effect of green manure will be more obvious and the yield will increase faster. 3.3 Integrated irrigation, pest, and weed management Good coordination of green manure with irrigation, pests and weeds management is the key to achieving sustainable production. Leguminous green manure can improve the soil's water retention capacity, especially in droughts, it can reduce irrigation water (Pál and Zsombik, 2022). Green manure grows fast and can cover the soil
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