Sulphur fertilizer reasonable application technology
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Sulfur, like nitrogen, phosphorus and potassium, is a nutrient element that is lacking in crop growth. Sulfur is indispensable for proteins, enzymes, and physiologically active substances in crops. Sulfur has unique effects in increasing crop yield and improving crop quality. The application of sulphur fertilizer can promote protein synthesis, increase the oil content of oil crops, increase the nitrogen fixation capacity of soybean crops, and increase the spicy odor of onion and garlic vegetables. Sulphur fertilizer has significant yield-increasing benefits in a variety of crops. According to the results of tests conducted by the International Institute for Sulfur Research in 1997 and 1998 in China, the average yield increase of major crops is above 6%-20%. Sulfur fertilizer not only increases crop yield but also improves crop quality and has significant economic benefits. The input-output ratio of sulfur fertilizer application is more than 1:3 on average. If sulfur fertilizer is used in sulfur-deficient soil, the input-output ratio can reach more than 1:9-10. The amount of sulfur required for crops is similar to that required for phosphorus. Some crops also require more sulfur than phosphorus, such as rapeseed, soybeans, peanuts, tobacco, sugarcane, and vegetables. In general, for every 1 ton of grain crops produced, such as rice and wheat crops require 3-4 kg of sulphur, legumes require 6-8 kg of sulphur, and oil crops require 10-12 kg of sulphur. Sulfur deficiency in crops can lead to growth retardation, leaf chlorosis or yellowing, small leaf area, and thin and weak stems, which are similar to nitrogen deficiency symptoms. The difference is that the chlorosis of the leaves first appears in the young leaves when sulfur deficiency occurs. Nitrogen deficiency is first manifested in the lower old leaves. The sulfur from which the crop grows comes from soil, fertilizers, algal water and the atmosphere. The total sulfur content of cultivated soil is 0.01%-0.05%, most of which is found in soil organic matter. The available sulfur that can be directly absorbed and utilized by crops is only less than 10% of the total sulfur content. Sulfur-containing fertilizers are an important source of supplemental soil sulphur. Rainfall and irrigation water also contain sulphur. The annual amount of sulphur that is dropped into the soil by rainwater is about 0.2-0.3 kg/mu. Sulphur dioxide in the atmosphere can be directly absorbed by plants. Sometimes half of the sulphur requirement of crops comes from the atmosphere. The normal concentration of sulfur dioxide in the atmosphere is 0.05 g/m3. If the content exceeds 1 g/m3, it will poison plants. Because the soil's available sulfur will be lost with water, the loss will be roughly equivalent to the amount of sulfur brought in by the rainwater. Therefore, the supply of sulfur in cultivated land mainly depends on fertilization. How to judge the lack of sulfur in soil and crops If the crop has the above-mentioned symptoms of sulfur deficiency, it can be used to determine the sulfur deficiency of crops. However, sometimes crops lack sulfur but there are no obvious symptoms; sometimes crop sulfur deficiency is also accompanied by the lack of other nutrients, or some kind of disease, whether the lack of sulfur is not easy to identify. For accurate diagnosis, quantification tests of soil sulfur and plant sulphur were carried out, as well as sulphur fertilizer tests. In general, the soil available sulfur content of 16 mg/kg soil is the sulfur deficiency index, below which soil is often insufficient for sulfur. Plants use dry matter total sulphur content as a nutrition assessment indicator. The general indicator for grass crops is 0.1% and cotton is 0.2%. The ratio of sulfur to nitrogen in crops can also be used as an index of sulfur nutrition status. Generally, the ratio of sulfur to nitrogen in leaf of field crops is 1:15-20. If the sulfur content is lower than this ratio, the crop may lack sulfur. Sulfur deficiency in farmland is becoming more and more serious. In recent years, large amounts of ammonium sulfate, urea, and other high-concentration non-sulfurized fertilizers have been used in recent years. The amount of sulfur-containing fertilizers such as superphosphate and ammonium sulfate has been reduced, and the amount of organic fertilizers and sulfur-containing pesticides has gradually decreased, resulting in annual reductions. The amount of sulfur applied to the soil decreases year by year. Second, the land multiple cropping index and crop yield increase, the amount of sulphur required for crop growth and the amount of sulphur taken away with the harvest, so that the soil sulfur content decreased year by year. Third, as the intensity of environmental pollution treatment is increased, the concentration of sulfur in the atmosphere and water is reduced, and the amount of sulphur obtained from the atmosphere and irrigation water is reduced. 4. Some soils with low content of organic matter and coarse texture have low sulfur content; in areas with high rainfall, more sulfur is lost from the leakage of drainage water, and the content of sulfur in soil decreases. Among the many causes of crop sulfur deficiency, the first three are the main reasons. According to the analysis results of more than 10,000 soil samples from 18 provinces and cities in China, 1/3 of the soil has a low effective sulfur content, among which sulfur deficiency conditions are common in the southern provinces and the Northeast. As the supply of sulfur-containing fertilizers is less than a year in a year, the demand for sulfur is increasing year-on-year due to the increase in grain production, and the sulphur fertilizer gap is increasing. In 1997, the sulphur deficit was 900,000 tons, in 2002. It has reached 1.5 million tons and is expected to reach 2.1 million tons in 2007. The situation is very serious. How to apply sulphur fertilizer rationally The currently used sulphurous fertilizers in China are mainly superphosphate and ammonium sulfate. Many compound fertilizers also contain different proportions of sulfur. Gypsum is an important sulfur fertilizer, slightly soluble in water, and should be ground before use to facilitate plant absorption and utilization. Sulfur is high in sulfur content, but it is hardly soluble in water. It is absorbed into crops after it is oxidized into sulphate by microorganisms. The fertilizer is slow but lasting. Crops are in need of sulphur peaks near the reproductive growth period. With the senescence of crops, the ability to absorb sulphur decreases. Therefore, sulphur should be applied before the reproductive growth period. It is better as a basal fertilizer and can be mixed with nitrogen, phosphorus, potassium and other fertilizers, combined with cultivated land. Into the soil. If sulfur deficiency is found during crop growth, fast-acting sulfur fertilizers such as ammonium sulfate can be used as topdressing or spraying. Sulfur iodide fertilizers should be applied early. They can be mixed with smashed soil and then spread to the soil along with the arable land. They can also be used as seed dressings or applied beside seeding ditch (holes) as seed fertilizers, and can also be used as mixed fertilizers. For rooting manure. The amount of fertilizer should be determined according to the amount of sulfur needed by the crop and the degree of sulfur deficiency in the soil. In general, 1.5-3 kg of sulfur per acre applied to the sulfur-deficient soil can meet the needs of the crop during the current season. For example, 20 kg of superphosphate or 10 kg of ammonium sulfate may be applied per acre, and 10 kg of gypsum powder or 2 kg of sulfur powder may be applied per acre.