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Sulfur deficiency symptoms and application of sulfur fertilizers in several crops
In recent years, due to the continuous increase of land multiple cropping index and crop yield, crops have increased sulfur nutrient absorption from the soil; in some places, due to changes in the use of chemical fertilizers, large quantities of non-sulfur-containing fertilizers such as phosphine and urea are applied, and superphosphate The use of sulfur-containing fertilizers such as calcium and ammonium sulfate is reduced; some soils with low organic matter content and coarse texture have low sulfur content; in areas with high rainfall, more sulfur is lost from rainwater and seepage water; environmental pollution treatment is increasingly strengthened, and the atmosphere The concentration of sulphur in the water and the reduction in the sulphur obtained from the atmosphere and in the irrigation water reduce the amount of organic manure and farm manure in recent years, and the supply of organic sulphur to the soil is becoming less and less. Therefore, it is easy to cause soil sulfur deficiency in some areas. Understanding the symptoms of sulfur deficiency in common crops and taking effective measures in time have a very important role in guiding agricultural production. First, the main crops lack of sulfur symptoms. When crops lack sulfur, their growth is hindered, their leaves are chlorotic or yellow, their leaf area is small, and their stems are weak and short, similar to the symptoms of nitrogen deficiency. The difference is that when the sulfur is lacking, the leaves turn green and yellow, first appearing in the young leaves; and the nitrogen deficiency is manifested first from the lower old leaves. 1, wheat: plant color light green, young leaves more obvious than the old leaves chlorosis, severe sulfur deficiency, brown spots appear on the leaves. 2, rape: The initial performance of the plant light green, young leaves paler than the old leaves, after the leaves gradually appear purple patches, curling up the edge of the leaves, late flowering knot, flower buds small and pale, short and thin roots. 3, rice: return to late-green, little or no tiller tiller, thin and thin plants, thin leaves and a small number of pieces, young leaves were light green or yellow-green, water-stained round brown spots on the tip of the leaves, dead coke. Dark brown roots, less white roots, delayed growth period. 4. Cotton: The plants are short and the whole plant becomes pale green or yellow-green, and the growth period is delayed. 5. Soybeans: The new leaves are pale green to yellow, and leaf veins are chlorotic, but the old leaves are still light green. The old leaves also lose green and yellow, and brown spots appear. The plants are thin, the roots are thin, and the nodules are stunted. 6. Tobacco: The whole plant is light green, the old leaves of the lower part are dry and the tips of the leaves are often curled, and some protruding bubble points also appear on the leaves. 7. Potatoes: Leaves and veins are usually yellowed. Symptoms are similar to nitrogen deficiency. However, the leaves do not fall off in advance. When the sulfur is extremely low, brown spots appear on the leaves. Second, the application of sulfur fertilizer technology 1, the application period: the crop in the vicinity of reproductive growth, the peak period of sulfur demand. As the crops age, the ability to absorb sulfur declines. Therefore, sulfur fertilizers should be applied before reproductive growth and better as a basal fertilizer. They can be mixed with fertilizers such as nitrogen, phosphorus and potassium, and combined with arable land. If sulfur deficiency is found during crop growth, fast-acting sulfur fertilizers such as ammonium sulfate, calcium persulfate, and potassium sulfate can be used as top dressing or foliar spray. 2. Application amount: The application amount of sulfur fertilizer should be determined according to the crop type and the degree of sulfur deficiency in the soil. Sulfur fertilizers should be applied to crops that require more sulfur in soils that lack sulfur. According to the results of field experiments conducted over many years, the appropriate sulfur application rates for several crops in Anhui Province are: 2 kg per mu for rice and wheat; 4 kg per mu for soybean; and 4-6 kg per mu for rape. In general, sulfur-bearing soils with 1.5-3 kg of sulfur per acre can meet the needs of seasonal crops. For example, 20 kg of calcium phosphate per acre or 10 kg of ammonium sulfate can be applied, and 10 kg of plaster or 2 kg of sulfur powder can also be applied. . In order to increase fertilizer efficiency, the amount of sulfur applied should be compatible with the amount of nitrogen and phosphorus applied, and the amount of nitrogen and phosphorus applied should be increased. The amount of sulfur applied should be increased accordingly. It is recommended that in wheat production, 10 kg of nitrogen should be applied per acre and 2 kg of sulfur should be applied. In soybean production, 3 kg of phosphorus should be applied per acre, and 3 kg of sulfur should be applied. 3. Application method: The sulphur fertilizer can be applied alone, or it can be mixed with NPK and combined with ploughing into the soil. Sulfur fertilizers should be applied early, can be mixed with fine soil or chemical fertilizers, ploughed into the soil as a base fertilizer, can also be seeded and applied to the seed ditch (holes) beside the seed fertilizer, but also mixed soil and fertilizer for the application of root fertilizer .