Detailed Explanation of Key Management Techniques for Soybeans During the Flowering and Podding Stage

During the flowering and podding stage, soybeans require thick, sturdy stems and dark green, thick leaves free of spots. Field management mainly focuses on preventing premature aging, controlling excessive vegetative growth, preserving flowers and increasing pods, and preventing shedding.

1. Skillful application of flower fertilizer

The flowering and podding stage is the period when soybeans absorb the most nutrients, and skillful application of flower fertilizer can generally increase yield by more than 15%. At the early flowering stage of soybeans, generally 5-10 kg of urea is applied per 667 sq m as a topdressing; for poorly growing plants, more should be applied, while for robust and luxuriant plants, less or no topdressing should be applied. In conjunction with nitrogen fertilizer application at the flowering stage, phosphorus, potassium, and trace element fertilizers such as boron and molybdenum should be sprayed on the leaves. Generally, 2 sprays are applied, each time per 667 sq m using 100 g of monopotassium phosphate, 25 g of ammonium molybdate, and 100 g of borax (first dissolved in a small amount of warm water), all added together to 50 kg of clean water and evenly sprayed on the stems and leaves of the plants.

2. Drought resistance and drainage

Soybeans have a high water requirement during the flowering and podding stage. They are particularly sensitive to moisture, and drought easily causes flower and pod drop. Therefore, under drought conditions, if leaves are found to be wilting at noon, irrigation should be carried out promptly to combat drought. However, flooding irrigation must be avoided, as it can easily cause root suffocation and rot, soil compaction, and cracking when dry, damaging the root system. Furrow irrigation with a small amount of water is preferable, just enough to moisten the soil. Soybeans have poor waterlogging tolerance and are susceptible to waterlogging damage. When there is excessive rain during the flowering and podding stage, attention should be paid to promptly clearing ditches and draining excess water.

3. Spraying hormones

1. Paclobutrazol

Paclobutrazol can control soybean plant height, shorten internode length, increase stem thickness, prevent lodging, increase the number of branches and pods per plant, improve seed-setting rate and grain weight, and promote the formation of top pods, generally increasing yield by more than 12%. It should be sprayed about 7 days after the beginning of flowering; for well-growing plants, it is appropriate to apply it somewhat earlier, before the beginning of flowering. Use 50-100 g of 15% paclobutrazol wettable powder per 667 sq m, diluted with 50 kg of water, and evenly spray both the front and back of the leaves. For indeterminate podding varieties, the spraying concentration can be higher; for determinate podding varieties, it should be lower. For poorly growing fields, it should be higher; for well-growing fields, it should be lower.

2. Sodium bisulfite

It is a photorespiration inhibitor. When applied to soybeans, it can reduce nutrient consumption from photorespiration, improve plant architecture, promote soybean root growth and increase the number of rhizobia, with good effects on preserving flowers and pods, increasing yield by more than 10%. Application method: spray once each at the early flowering stage and the full flowering stage, each time using 10 g of sodium bisulfite per 667 sq m, diluted with 75 kg of water, and choose to spray the leaves in the afternoon when sunlight is not too intense. Photosynthetic trace element fertilizer (100 g per 667 sq m) can also be mixed with monopotassium phosphate for spraying.