Soybean normal fertility requires more nitrogen, phosphorus, and potassium nutrients, followed by calcium, sulfur, magnesium, and trace elements such as molybdenum, boron, and manganese. From the branching stage, the absorption and accumulation of nitrogen gradually increased with the growth of the plant, and reached the maximum at the grain; the peak of phosphorus absorption was during the branching-crusting stage, and the phosphorus uptake from seedling to anthesis was not significant, but It has a great influence on the whole growth period. Pre-fertility more potassium absorption, potassium absorption after scab peak.
First, the lack of symptoms of soybean
Nitrogen deficiency: The amount of nitrogen needed for the whole growth period of soybeans was 4-5 times higher than that of cereals of the same amount. The soybean-deficient nitrogen plants had short growth, few branches, light pale green or yellow-green leaves, and uniform color, especially the first yellow leaves of the base.
Potassium deficiency: Soybeans are prone to potassium deficiency, and symptoms occur when 5-6 leaves are present. The middle and lower leaf margins are "gold-rimmed" due to loss of green. The old veins protrude from the wrinkled edges and the petioles turn brown. The knot is thin and the grains are more. Phosphorus deficiency: When soybeans lack phosphorus, brown spots appear on leaves after flowering, and seeds are small. Severe stems and leaves are dark red, nodule development is poor. Calcium deficiency: When the soybean is deficient in calcium, the new leaves do not stretch and the old leaves have gray spots. Veins brown, petiole soft drooping. The dark brown is fragile and sticky. The junction between the petiole and the leaf blade is dark brown. In severe cases, the top of the stem curls and it hangs like a hook. Symptoms of magnesium deficiency are the first true leaves, and the middle and lower leaves of adult plants fade first, then they are orange or orange-red. However, the veins remain green, and the mesophyll of the veins often bulges slightly to make the leaves wrinkle.
Zinc deficiency: When soybeans are deficient in zinc, they grow slowly, yellowing between veins, and the leaves appear faded spots with lemon yellow, gradually expanding and forming necrotic plaques, followed by necrotic tissue shedding.
Boron deficiency: Soybean lack of boron into the top of the bud to stop growing the next volume, atrophy and dwarfing, chlorosis between veins, the tip of the curve, the rough old leaves thickened, the main root tip death, lateral roots and more short, nodule dysplasia. After flowering, shedding more, less pods, more deformed. Deficient in molybdenum: the leaves are thick and wrinkled, and the leaves are faded. There are many tiny gray-brown spots. The edges of the leaves curl upwards and they are cup-shaped. The number of nodules on the roots is small and the root nodule is also small and the growth and development are poor.
Second, control methods
The requirement of large amounts and trace elements for soybeans to be satisfied from the soil depends on the abundance of trace elements in the soil and the environmental conditions of the plant roots. In our county, the soil is mostly yellow-fluid soil, and boron, molybdenum, and zinc fertilizers are frequently encountered in the soil. The appropriate amount of nitrogen, phosphorus and potassium fertilizers plays an important role in improving the quality of soybeans. Therefore, we should master the following points when growing soybeans:
(1) Dressing of trace elements with ammonium molybdate and borax, 3 grams of ammonium molybdate per kilogram of seed, 2 kg of borax and 0.1 kg of hot water to make it melt, wait until the air cools and mix with seeds to promote root nodules Well developed.
(B) the application of fertilizer base fertilizer is best to use farmyard fertilizer, when planting soil before sowing, usually 3-4 square meters per hectare of farmyard fertilizer, or cake fat 40-50 kg. The principle of fertilization is mainly phosphorus fertilizer, supplemented by nitrogen fertilizer. Apply 15 kg of compound fertilizer or 25 kg of soybean fertilizer per acre, and apply it when sowing the soil.
(3) The principles that should be mastered in the top-dressing period of top-dressing top-dressing growth period are the application of phosphorus in the early growth period and the increase of nitrogen in the later period. About 5 days before the initial flowering, soybeans should be topdressed once, and 5 kg of urea, 10-15 kg of diammonium phosphate, and 10 kg of potassium chloride can be applied per acre. The topdressing method should be applied in combination with the cultivator. For fields where base fertilizer cannot be applied, fertilizer should be applied early in the seedling stage. After the flowering of soybean, its own nitrogen fixation capacity can no longer meet its rapid growth and development needs, and soybean is sensitive to phosphorus. Therefore, in the later period of crop growth, topdressing and foliar spray fertilizer should be carried out, with 0.5 kg of urea per mu and 150 g of potassium dihydrogen phosphate. Adding 25 grams of ammonium molybdate, 75 grams of borax and 50 kilograms of water to increase the rate of soybean flowering and scarring.
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