Legume Genomics and Genetics 2025, Vol.16, No.6, 270-278 http://cropscipublisher.com/index.php/lgg 272 nutrient requirements can better absorb nutrients from the soil and improve resistance to problems such as pests and drought (De Mazancourt et al., 2022). There is a method called "4C" (competition, complementarity, cooperation and compensation) that can help us understand how these crops affect each other (Watson et al., 2021). In addition, arranging the proportion and planting layout of leguminous crops can further improve yields and resource utilization, increase income, and make agriculture more sustainable (Liu et al., 2024). 3 Intercropping Strategies Involving Leguminous Crops 3.1 Strip intercropping: arrangement, spatial benefits, and root zone management To put it simply, strip intercropping is to plant leguminous crops and non-leguminous crops in strips. You can imagine a field where a strip of soybeans is planted first, and then a strip of corn is planted. The strips are close to each other but independent of each other. In this way, each crop stays in its own root zone to absorb water and fertilizer safely, and can share excess resources at the junction of the strips. The design of the strips allows for more uniform sunlight exposure, and a more reasonable distribution of water and nutrients, resulting in higher yields and a more stable system. Take soybean-corn strip intercropping as an example. This combination has significantly increased crop productivity and resource utilization in many field trials, which has greatly helped China's food security and sustainable agriculture (Liu and Yang, 2024). If each strip is changed to "double-row" planting, that is, two rows of crops are planted in one strip, it can further reduce the competition between similar crops, making the yields of corn and leguminous partners more stable and higher. 3.2 Relay intercropping: sequential sowing to optimize temporal resource use The idea of intercropping is different from that of strip intercropping. It relies on "time difference" to reduce competition. The method is very simple: plant one crop first, let it germinate, grow, and harvest first, and when it is almost finished, sow another crop. In this way, the light, water, and fertilizer consumed by the two crops are basically staggered, and they don't fight too much. Adding up the whole season, the land is more fully utilized and resources are less wasted. For example, the "relay race" mode of corn and pigeon peas is that corn comes on stage first, and pigeon peas follow up. In many areas, such relay planting can achieve higher total yields and better land utilization effects than planting only corn or only pigeon peas (Thierfelder et al., 2020). 3.3 Mixed intercropping: biodiversity enhancement and weed suppression in legume-cereal systems Mixed intercropping refers to the direct intercropping of legumes and cereals, with wider or narrower row spacing, not requiring uniformity but seeking complementarity. With more plant species in the field, it is not easy for pests and pathogens to target them, and it is more difficult for weeds to take root, so pesticides and herbicides are naturally used less frequently. What's even better is that legumes can "catch" nitrogen from the air through nitrogen fixation and turn it into nutrients in the soil, which is equivalent to applying a layer of "nitrogen fertilizer" to cereals for free (Carlsson et al., 2020; Hossain et al., 2021). A large number of studies have shown that legume-cereal intercropping can not only improve land productivity, but also reduce yield fluctuations and make the system more resilient. For small farmers and low-input planting environments, this mixed method is a good key to stable production and increased income (Njira et al., 2024). 4 Agronomic and Environmental Benefits 4.1 Enhanced nitrogen use efficiency and soil fertility improvement In intercropping systems, especially those involving legumes, nitrogen utilization efficiency can be significantly improved, and the soil becomes more fertile. There are symbiotic bacteria on the roots of legumes, which "pull" nitrogen from the air into the soil and supplement fertilizer in a natural way, so synthetic fertilizers can be used much less. After the nitrogen is fixed, the legumes themselves benefit first, and the crops next to them can also share the benefits. Over time, the total nitrogen reserves in the field slowly increase, and organic matter accumulates step by step (Pelzer et al., 2020; Hossain et al., 2021). Sufficient nitrogen and fertile soil, these two points work together to keep the farmland healthy in the long term and make the agricultural system more sustainable.
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