Key Technical Points for Scientific Management of Soybeans Adapted to Seedling Conditions

Liang Huizhen, associate researcher at the Cash Crop Research Institute of the Provincial Academy of Agricultural Sciences, said that at present most areas of our province's soybeans are at the flowering and podding stage, which is the period of greatest nutrient and water uptake and also the peak period of root nodule nitrogen fixation. The main goal at this stage is to promote more flowering and more pod setting, prevent premature senescence, control excessive vegetative growth, increase flowers and preserve pods, reduce shedding, and lay the foundation for a high yield.

Due to the tight time schedule at sowing, summer soybeans often receive no or little basal fertilizer, and by the time the soybeans set pods, nutrient deficiency occurs, so flower and pod fertilizer should be applied promptly. At the soybean flowering and podding stage (earlier for poor-growing plants, later for vigorous-growing plants), apply 5-10 kg of urea per mu. If the soil has a strong fertilizer supply capacity and the plants grow robustly, apply less or none, so as to avoid excessive vegetative growth that causes lodging or shedding of flowers and pods. In combination with nitrogen fertilizer application, foliar spraying of phosphorus and potassium fertilizers and micro-fertilizers such as boron and molybdenum can improve quality, promote maturity, and has a very good yield-increasing effect. Generally spray about 2 times, each time using 100 g of potassium dihydrogen phosphate, 25 g of ammonium molybdate, and 100 g of borax per mu (first dissolve the ammonium molybdate and borax in a small amount of warm water), dilute with 50 kg of water, and spray evenly.

In some places, soybeans showed excessive vegetative growth after rain, which can be handled by manual topping. Topping means pinching off the 2 cm growing tip of the main stem at the full-flowering or final-flowering stage; varieties with a determinate podding habit and poor barren land are not suitable for topping.

Lu Weiguo, associate researcher at the Cash Crop Research Institute of the Provincial Academy of Agricultural Sciences, told reporters that recently the Huang-Huai region has had relatively heavy rainfall and rising temperatures, entering the hottest mid-fu period, and soybeans have entered a rapid growth period. At the same time, because rainfall and irrigation conditions varied greatly across regions when soybeans were sown in June this year, sowing dates were inconsistent. According to different sowing dates and soybean growth conditions, the following management measures should be taken:

Normally sown soybeans, that is, soybeans sown before June 20, are already at the flowering and podding stage and have entered the period when vegetative growth and reproductive growth proceed together, so adequate water and fertilizer supply should be ensured. For soybeans growing excessively after rain, spraying growth regulators such as triiodobenzoic acid and paclobutrazol at the early flowering stage can control excessive vegetative growth. If the excessive growth is severe, spray once more at the full-flowering stage. In rainy weather, pay attention to drainage.

Late-sown soybeans, that is, soybeans sown after June 20, are mostly at the branching stage, while early-maturing varieties are at the early flowering stage. Topdressing at this time has a very good yield-increasing effect. The amount of topdressing should be determined according to soil fertility and soybean growth conditions; plots with high fertility and excessive growth should not be topdressed. Topdressing should pay attention to the combination of nitrogen and phosphorus fertilizers. In the late flowering and podding stage, no more topdressing should be done, only foliar spraying, such as potassium dihydrogen phosphate and Dizhongbao. Soybeans tending to grow excessively should be deep-hoed to injure part of the fine surface roots, promote deeper root growth, and prevent lodging.