The sowing date of summer soybeans is in the busy season of “three summers”. The farmers with insufficient labor are planting under the condition of no soil fertilization. The nutrients needed for soybeans depend on the nutrients remaining in the soil before the crops and the growth period of soybeans. top dressing. Therefore, top dressing plays an important role in increasing soybean yield. Its topdressing skills are as follows:

Early application of seedling

Soybeans need to absorb nutrients from the soil after emergence. Although the amount of fertilizer is not large, but the soybean root nodules are still in the formation stage, the nitrogen fixation ability is very weak. If the nitrogen nutrient supply is insufficient, it is easy to cause the seedlings to become "starved". Caused by poor growth, it will inevitably affect the early development of strong seedlings, which is not conducive to high yield of soybeans. Early seedlings can promote the growth of roots and leaves, so that the young stems are thick and the axillary buds differentiate rapidly. Generally, when the first compound leaves are unfolded, the urea is 3 to 5 kg per mu. Do not apply too much nitrogen fertilizer, too much nitrogen fixation will inhibit the development of rhizobium, which is not conducive to high yield of soybean. Soybean seedlings are sensitive to phosphorus reaction. Appropriate amount of phosphate fertilizer in seedling stage is beneficial to promote the formation and development of soybean nodule. Generally, 7.5~15 kg of calcium phosphate is applied per acre, and cultivating after application.

Skillful application of flower fertilizer

Soybean flower pod period is the period in which soybeans absorb the most nutrients in their lifetime. Applying appropriate amount of nitrogen fertilizer before flowering or early flowering can reduce the loss of flower pods, and obviously increase the yield, which can increase the yield by about 20%. Generally, 5 to 7.5 kg of urea per acre is used, and the fertilizer is applied after the dew is dried, and then the cultivation is carried out. If the soil is fertile and the plant grows robustly, it should be less or not traced to the nitrogen fertilizer to prevent it from growing. If the application of phosphate fertilizer is insufficient at the time of sowing, it should be supplemented at this time, and 7-10 kg of calcium phosphate per acre is applied.

Spraying granular fertilizer

After the soybean enters the pod blast stage, the nitrogen fixation capacity and root activity of Rhizobium gradually decline, and the ability to absorb fertilizer is weakened. At this time, foliar spray fertilizer should be used to supplement nutrients, so as to increase the source of Zhuangzi, reduce shedding, and increase soybean yield. quality. Generally, 50 kg of 0.4% potassium dihydrogen phosphate solution per mu is used, sprayed on soybean leaves on cloudy or sunny days, spray once every 7~10 days, and spray 2~3 times. If the plant has denitrification and premature aging, add 0.5 kg of urea per acre.

Replenishing micro-fertilizer

Trace elements are also indispensable in the growth and development of soybean. For example, if the soybean is deficient in magnesium, the old leaves are grayish green, and yellow spots are formed between the veins. The 0.5% magnesium sulfate solution should be sprayed on the leaves in time; the manganese deficiency in soybeans is first manifested on the new leaves, and the rest is yellow except for the veins. It is necessary to spray 0.05% manganese sulfate solution in time; the soybean is deficient in molybdenum, the young leaves are yellow-green, and the chlorosis is formed between the veins and the swelling is downward. The 0.05% ammonium molybdate solution should be sprayed in time. The amount of foliar spray fertilizer is small, and it can be sprayed once every 7~10 days, even for 2~3 times. In addition, soybean is also sensitive to boron. Boron deficiency can affect normal growth and development, causing flower pods to fall off. 0.2% borax solution can be sprayed once in the seedling stage and the initial flowering stage.