Field Crop 2025, Vol.8, No.6, 258-264 http://cropscipublisher.com/index.php/fc 260 4 Effects on Soybean Growth Parameters 4.1 Emergence rate, seedling establishment, and plant vigor Soybeans need sufficient nutrients and good soil conditions from germination to seedling growth. With sufficient nutrients, especially after the use of organic fertilizers, seedlings grow faster and have stronger vitality. Studies have found that if the light conditions are good, the weight of the aboveground part and the roots will increase, the stems will be thicker, and the leaves will become larger (Figure 1) (Huynh et al., 2025). Some organic fertilizers can also improve soil structure, especially when the soil acidity is high, which helps to increase the germination rate and the health of seedlings (Sattar et al., 2023). Figure 1 Soybean seedlings: (a) A0_11, high light intensity, uniform PPFD distribution; (b) B0_11, nonuniform PPFD distribution. Discoloration of leaves indicates nutrient deficiency symptoms (Adopted from Huynh et al., 2025) 4.2 Plant height, number of branches, and LAI changes Plant height, number of branches and leaf area index are several important indicators to measure whether soybeans grow well. If nutrients are managed properly, such as using organic fertilizers, the plants will grow taller, the leaves will become larger, and some can even increase branches. Studies have found that after taking these measures, plant height can be increased by 21%, leaf area by 18.7%, and leaf dry weight can even increase by 66.4% (Wang et al., 2025). However, if high temperature or drought occurs, the leaves may become smaller, with fewer branches, and the whole plant will be shorter, all of which will lead to a decrease in yield (Hu and Wiatrak, 2012; Jumrani and Bhatia, 2018). At this time, if organic fertilizers with good water retention are added, these adverse effects can be alleviated and the plants can continue to grow normally. 4.3 Root activity and nodulation dynamics The health of the roots is directly related to the ability of soybeans to absorb water and nutrients, and also affects biological nitrogen fixation. Using organic fertilizers and some beneficial bacteria, such as growth-promoting bacteria or mycorrhizal fungi, can make the roots grow more and longer, with a larger surface area, and the number of nodules will also increase, up to 68% more (Ngosong et al., 2022). These changes are related to increased acid phosphatase activity in the rhizosphere, an enzyme that helps plants absorb nutrients and thus increase yields. Good nodule growth can also increase the content of protein, sugar, and trace elements in the grains, indicating that the relationship between roots and microorganisms is important for high soybean yields. 5 Impacts on Yield and Seed Quality 5.1 Pod number per plant, 100-seed weight, and total yield The yield of soybean mainly depends on three aspects: the number of pods per plant, the size of seeds (that is, the 100-grain weight), and the total harvest. Scientific nutrient management, such as replacing chemical fertilizers with part of organic fertilizers, is helpful in these aspects. Experiments have found that when nutrients are more
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