Sulfur is one of the 16 nutrients necessary for crops. The application of sulphur fertilizer in China's sulfur-deficient areas can generally increase crop yield by 15%-20% and improve crop quality. Tests show that citrus, soybean, sugar cane, peanut, sweet potato, tea and other crops have a significant increase in sulfur application, generally more than 10%.
The causes of crop sulphur deficiency vary. First, the soil itself is deficient in sulfur. For most red soils in the south, the sulfur content is low, generally below 0.03%, while the available phosphorus is only 16-30 ppm. In the production, the sulfur deficiency of crops is extremely common due to the imbalance of nitrogen and sulfur ratio. With the large application of nitrogen fertilizer, there will be different degrees of sulfur deficiency. Second, with the increase in multiple cropping indices and yield per unit area, more and more sulfur is removed from the soil. At present, fertilizer varieties are constantly pursuing high concentrations. In particular, most manufacturers replace urea sulfate with urea, ammonium phosphate instead of calcium phosphate, potassium chloride instead of potassium sulfate, and chemical fertilizers containing sulfur are decreasing, making the sulfur needed in the soil unable to make ends meet. . The third is the use of heavy calcium fertilizer. In the past, when low concentrations of calcium were applied, there was no problem of sulfur deficiency in the soil, because the main component in calcium is monocalcium phosphate and the secondary component is calcium sulfate. Therefore, calcium can make crops obtain sulfur nutrition, and in some places, heavy superphosphate is applied all the year round. This fertilizer has been improved in the manufacturing method, so that the fertilizer does not contain impurities such as calcium sulfate, but natural sulfur deficiency occurs frequently after perennial application. problem.
When the crop is deficient in sulfur, its appearance symptoms are similar to nitrogen deficiency, the leaves are light green or yellow, and the deficiency occurs on the leaves of young leaves. Generally, the young shoots turn yellow, the leaves are green and yellow, and the plants are yellow and uniform. It is thin, the roots are slender and not branched, the flowering is delayed, and the fruit is reduced. The symptoms of nitrogen deficiency begin with the lower old leaves, and the symptoms of sulfur deficiency begin with the upper new leaves, which are easy to distinguish. The sulphur deficiency of rapeseed and cotton often shows that flowering continues continuously, flower buds cannot develop, seeds are not fully developed, and plants are dwarfed. When the rice is deficient in sulfur, the greening is slow, no tillering or less tillering, the plant is thin and short, the leaves are thin, the young leaves are pale green or yellow-green, the tip of the leaves is water-soaked round brown spots, the tip of the leaves is scorched, and the roots are dark brown. , white roots are less, and the growth period is delayed. Vegetables are deficient in sulfur, plants are generally chlorotic, and later growth is inhibited. Generally, firstly, the yellowing of the young leaves (buds) begins throughout the whole leaf, and when it is severe, it turns white, and the veins do not leave green. The stem is thin, the root is slender and not branched, the flowering is delayed, the shell rate is high, and the fruit is small. Leguminosae and cruciferous and onion garlic crops are prone to sulfur deficiency.
At present, sulfur fertilizers suitable for crop application mainly include sulfur powder, superphosphate, potassium sulfate, ammonium sulfate and gypsum powder. Due to different crop types, soil types and fertilization purposes, the application amount, application method and fertilization period of sulfur fertilizer are different, and the amount of application is generally more than that of application and acupoint application. Water-soluble fertilizers (such as sulphate sulphur fertilizer) can be used as base fertilizer, top dressing and seed fertilizer; water-insoluble fertilizers (such as sulphur-based sulphur fertilizer) are generally used as base fertilizers, and should be applied as base fertilizers. Sulfate fertilizers are generally recommended. Such as ammonium sulfate, superphosphate, gypsum, potassium sulfate and the like. Sulfur fertilizers have highly dispersible granular sulfur fertilizers. The recommended amount of sulphur fertilizer for different crops is different. The recommended amount of sulphur fertilizer is 1.3-2.7 kg/mu for cereals, 2.4 kg/mu for beans, oils and vegetables, and 2.7-5.3 kg/mu for sugar. At the same time, the application of sulfur fertilizer should be combined with nitrogen, phosphorus and potassium to achieve nutrient balance. To achieve optimal growth of the crop, the ratio of nitrogen to sulfur in the plant is 15:1-20:1. When crops are fertilized, the ratio of nitrogen to sulfur is generally 7:1, and the ratio of phosphorus pentoxide to sulfur is 3:1.
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