Molecular Soil Biology 2025, Vol.16, No.3, 126-136 http://bioscipublisher.com/index.php/msb 130 al., 2024). Second, too much nitrogen fertilizer will cause too much nitrate and hydrocyanic acid (HCN) to accumulate in the soil and plants. If there is a drought, it will be even more serious, and the safety of food and feed will become a problem (Shehab and Guo, 2021; Wang et al., 2024). Studies have shown that when the amount of nitrogen fertilizer exceeds 90 to 120 kg/hectare, the HCN level in the plant will rise rapidly, and the antioxidant capacity will decrease. Therefore, in arid areas, nitrogen fertilizer should not be applied too much, and yield, quality and safety must be taken into account (Shehab and Guo, 2021; Wang et al., 2024). Using too much nitrogen fertilizer will reduce fertilizer efficiency and increase the risk of environmental pollution, leading to nitrogen loss. 6 Phosphorus and Potassium Nutrition 6.1 Phosphorus: Root development, flowering, seed setting Phosphorus is a very important nutrient in sorghum growth, especially when it grows roots, flowers and sets seeds. If there is enough phosphorus fertilizer, sorghum can grow more vigorously, accumulate more nutrients and have higher yields (Schlegel and Havlin, 2021; Guo et al., 2025). Some long-term field experiments have found that phosphorus fertilizer can not only increase grain yield, but also help the absorption of nitrogen fertilizer, saving fertilizer and money (Schlegel and Havlin, 2021). In addition, phosphorus is mostly concentrated in the grains, so it has a great impact on the final yield and quality (Ivanina et al., 2021). In saline-alkali land, if 60 kg/hectare of phosphorus fertilizer is used together with nitrogen fertilizer, the harvest index and nutrient absorption effect of sorghum can be significantly improved (Guo et al., 2025). 6.2 Potassium: Disease resistance, drought tolerance, grain filling Potassium is also critical for sorghum, especially in disease resistance, drought resistance and grain filling. Potassium is mainly stored in the stems of sorghum, which can enhance the resistance of the plant and help maintain water balance (Ivanina et al., 2021). Studies have found that when more nitrogen fertilizer is applied, the potassium content in the leaves and stems of sorghum will also increase, so that dry matter accumulation will increase and yield will increase (Kostadinova et al., 2018; Todorov et al., 2020). If potassium fertilizer is applied properly, it can make sorghum photosynthesis more efficient and have better nutritional quality. The effect of potassium fertilizer is particularly obvious in difficult environments such as drought or saline-alkali land (Abbaszadeh-Dahaji et al., 2020; Gulzhaina et al., 2025). With more potassium, the grains are fuller, and the yield and quality are naturally better (Ivanina et al., 2021; Guo et al., 2025). 6.3 Synergistic and antagonistic interactions with nitrogen Nitrogen, phosphorus, and potassium affect each other. Many studies have found that applying nitrogen and phosphorus together is better than applying them separately. This combination can increase grain yield and make fertilizer utilization more efficient (Zhu et al., 2020; Schlegel and Havlin, 2021; Guo et al., 2025) (Figure 2). When there is more nitrogen fertilizer, plants absorb phosphorus and potassium more strongly. In other words, phosphorus and potassium can be better absorbed and utilized only when there is enough nitrogen fertilizer (Kostadinova et al., 2018; Todorov et al., 2020). But if all three nutrients are lacking, nitrogen is often the first to be affected. Insufficient nitrogen will slow down the overall growth of sorghum and also reduce the absorption of phosphorus and potassium (Zhu et al., 2020). Scientifically combining nitrogen, phosphorus and potassium fertilizers is the key to improving sorghum yield and quality. This not only makes good use of nutrients, but is also more environmentally friendly and sustainable. 7 Organic and Bio-based Fertilizers 7.1 Impact on soil health and microbial activity Organic and biofertilizers are very good for soil. They make soil healthier and increase the variety and activity of microorganisms in the soil. For example, using materials such as cow dung and pine needles together with organic acids and beneficial bacteria (such as Priestia megateriumand Trichoderma harzianum) can reduce salt in the soil, increase nutrients, and promote better root growth and photosynthesis, which is very helpful for the growth of sweet sorghum (Xue et al., 2024). In Burkina Faso, studies have found that after using organic fertilizers such as Bokashi, the organic matter content of the soil increased, and there were more large animals in the soil, with a
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