Field Crop 2025, Vol.8, No.5, 231-237 http://cropscipublisher.com/index.php/fc 235 make the soil more fertile and beans grow better. For example, applying biochar and phosphate fertilizer together can increase the pH value, nitrogen and phosphorus content of the soil, and allow the soil to capture more nutrients. These improvements allow cowpea roots and leaves to grow more nodules and increase beneficial plant components (Table 1) (Phares et al., 2020). These results show that data-guided fertilization methods can help us stabilize production and improve quality in modern agriculture. Table 1 Rhizosphere soil properties following application of biochar and inorganic phosphorus fertilizer (TSP) (n = 3) (Adopted from Phares et al., 2020) Treatment pH TotalN(%) AvP (mg/kg) SOC (%) CEC (cmolc/kg) Control 5.43 ± 0.03a 0.09 ± 0.02a 7.34 ± 0.09a 0.72 ± 0.00a 4.43 ± 0.10a BC1.5 5.83 ± 0.03b 0.22 ± 0.04b 11.25 ± 0.43b 1.12 ± 0.03b 5.05 ± 0.07b BC2.5 6.10 ± 0.01c 0.30 ± 0.02c 13.92 ± 0.67c 1.34 ± 0.02c 6.38 ± 0.05c BC1.5+P 5.86 ± 0.01b 0.36 ± 0.03d 23.52 ± 0.79d 1.16 ± 0.04b 5.08 ± 0.10b BC2.5+P 6.11 ± 0.01c 0.43 ± 0.03e 26.78 ± 0.65e 1.36 ± 0.02c 6.41 ± 0.04c %CV 0.4 9.5 3.5 2.3 1.4 Table caption: BC1.5 = biochar at 1.5 t/ha, BC2.5 = biochar at 2.5 t/ha, P = phosphorus fertilizer; CV: coefficient of variation, AvP = available phosphorus, SOC = soil organic carbon, CEC = cation exchange capacity. Each value is presented as mean ±1 standard deviation. Means in the same column and lettered with same alphabet superscripts are not significantly different at p < 0.05 using Fisher's protected LSD test (Adopted from Phares et al., 2020) 7.2 Farmers’ self-management plot experiment in Heng County, Guangxi In Heng County, Guangxi, local farmers also used soil testing and formula methods to grow cowpeas. Through field experiments, they used a method called "crop response model (STCR)" to determine the amount of nitrogen, phosphorus and potassium fertilizers based on the actual soil conditions. This method is also equipped with a calculator and fertilization formula, which is very convenient to use. As a result, farmers not only save fertilizer, but also increase the yield of green beans and use nutrients more evenly. These practices show that even small-scale growers can grow well and make more money as long as they use scientific methods. 7.3 Case study of greenhouse for facility agriculture in Weifang, Shandong Soil testing and formula fertilization have also been tried in some greenhouses in Weifang, Shandong. Under this facility agriculture condition, farmers first do soil tests, and then use water-soluble fertilizers with irrigation to deliver fertilizers directly to the roots of crops. In this way, the yield of seeds and stems is increased, and the main nutrients in the soil are better absorbed (Jayanthi et al., 2024). Coupled with modern irrigation technology and sophisticated nutrient management, cowpeas can grow fast and well, and keep the soil healthy. This method is particularly suitable for efficient planting in greenhouses. 8 Concluding Remarks In cowpea cultivation, soil testing and formula fertilization is a very practical technological advancement. The core of this method is to first test the nutritional status of the soil, and then give reasonable fertilization suggestions based on the target yield. Farmers can use chemical fertilizers and organic fertilizers (such as biochar, compost, and green manure) together based on these suggestions, which can not only increase soil fertility but also increase cowpea yield. At the same time, this practice can also improve some important indicators of the soil, such as pH value, organic carbon content, and nutrient utilization rate. Under the premise of ensuring yield, it can reduce the use of chemical fertilizers, which is beneficial to environmental protection and sustainable development. However, there are also some practical problems in the application process. The soil types, climatic conditions, and farming methods in different regions vary greatly, which may lead to different effects of the same method. In addition, farmers in some areas have difficulty in obtaining soil testing services and do not have a deep understanding of formula fertilization. Some formula suggestions are too general and lack guidance for specific plots. In order to solve these problems, it is necessary to increase the promotion of technology, provide reasonably priced and easy-to-use soil testing services, and promote comprehensive fertilization plans in combination with
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