Sulfur is one of the 16 nutrients necessary for crops . It is the basic element that constitutes sulfur-containing amino acids and proteins , and is also an important component in the synthesis of other physiologically active substances, directly involved in the metabolism of crops. Rational application of sulphur fertilizer plays an important role in improving rice yield and improving quality.
1. Rice's demand for sulfur and grading standards Sulfur is an essential nutrient element for rice growth and development. Sulfur is a component of many important enzymes in rice , affecting nitrogen metabolism, such as amino acid, protein synthesis, nitrate reduction, etc.; carbon metabolism, such as photosynthesis, carbohydrate and sugar synthesis, fat metabolism, etc. have important effects. Sulfur is an essential component of the essential amino acid methionine, methionine is the amino acid initiation of protein synthesis, it is reasonable Sulfur could significantly increase the protein content of the rice, and to improve the nutritional quality of rice. The sulphur content of rice stems and leaves is similar to that of phosphorus, which is 0.15-0.30% . The effective sulfur grading standards for paddy soils are: severe sulfur deficiency <12 mg / kg, sulfur deficiency 12-20 mg / kg, potential sulfur deficiency 20-30 mg / kg, sulfur medium 30-40 mg / kg, rich in sulfur > 40 mg / kg.
Second, symptoms of sulfur deficiency paddy rice while sulfur deficiency, dwarf plants thin, leaf yellowing; small number of thin sheet leaf, pale green or yellow-green leaves; poor root growth, dark brown. After transplanting, the hair roots are less, the greening is slower, the tillers are less or not divided; the growth period is delayed, and the yield is reduced.
The leaves of sulfur deficiency all turn yellow, the old leaves are more serious than the young leaves, and the leaves become smaller, similar to nitrogen deficiency. However, in the absence of nitrogen, yellowing starts from the tip of the blade ; in the case of sulfur deficiency, the entire blade is yellowed. In southern China, the phenomenon of “sittingâ€, which is slow in growth and the yellowing of leaves, is often associated with sulfur deficiency.
Third, the method of rational application of sulphur fertilizer in rice (I) during the application period of rice in the vicinity of reproductive growth, is the peak period of demand for sulfur. As the growth period progresses, the ability to absorb sulfur decreases. Therefore, the sulfur fertilizer should be applied before the reproductive growth, and the base fertilizer is better applied. It can be mixed with fertilizers such as nitrogen, phosphorus and potassium, and combined with the cultivated land to be applied to the soil. If sulfur deficiency is found during crop growth, quick-acting sulfur fertilizer can be used for top dressing or page spraying.
(2) The application rate of sulfur fertilizer should be determined according to the crop variety and the degree of soil sulfur deficiency. In the soil with more sulfur deficiency, more sulfur fertilizer should be applied. Studies have shown that the recommended amount of sulfur per mu in rice is 2-4 kg. Sulfur fertilizer should be used together with nitrogen, phosphorus and potassium fertilizer to achieve nutrient balance and improve fertilizer efficiency.
Sunny potassium fertilizer 5-12% sulfur, can fully meet the demand for sulfur in rice, it is recommended to use directly Sunny potassium compound fertilizer, nitrogen, phosphorus, potassium, sulfur four complete nutrition. The base fertilizer is 20-40 kg per mu, and the topdressing fertilizer is 10-20 kg per mu .
IV. Increasing yield and increasing yield of rice sulfur application Applying sulfur fertilizer can effectively correct rice sulfur deficiency. However, many factors affect the effects of sulfur fertilizers, such as crop rotation system, growing season, soil type and organic matter content, as well as sulfur content in rainwater and irrigation water. According to the test report in recent years, the application rate of 2.0-4.0 per mu is based on pure sulfur, and the yield increase is 1.5-12.0% , with an average yield increase of 4.7% .
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