An Introduction to the Characteristics and Scientific Application Methods of Sulfur-Containing Urea

Sulfur-containing urea is a nitrogen fertilizer made by introducing sulfur into ordinary urea. There are two common forms: one in which sulfur is incorporated into the interior of the granule during granulation, and another in which sulfur is coated onto the surface of the urea granule. Whichever form it takes, it supplies both nitrogen and sulfur nutrients to the soil.

Compared with ordinary urea, the most prominent feature of sulfur-containing urea is that it supplies nitrogen and sulfur together. Sulfur is one of the essential secondary elements for crop growth, participating in protein synthesis and various metabolic processes. It has a positive effect on increasing the oil content of crops such as rapeseed and peanut, as well as the flavor quality of Liliaceae crops such as garlic and onion. On sulfur-deficient soils or for sulfur-loving crops, the nutrient supply is often more complete than with ordinary urea alone.

From an application standpoint, sulfur-containing urea can be used as a base fertilizer and as a topdressing. It is especially suitable for crops with high sulfur requirements, such as Brassicaceae, Liliaceae and Fabaceae. When applying, it should be placed deep and covered with soil to reduce nitrogen loss through volatilization as ammonia; when used as a seed fertilizer, it should be kept at a certain distance from the seeds to prevent burning the seeds and seedlings. Sulfur-coated granules are relatively hard, so there is no need to crush them deliberately before application, lest their slow-release structure be damaged.

It should be noted that sulfur, after oxidizing in the soil, produces an acidic reaction. In fields that are already strongly acidic, when applying it heavily over the long term, it should be reasonably adjusted according to the soil pH, with improvement measures such as lime applied when necessary. During storage, keep it in a dry, ventilated place, and guard against moisture and caking. Overall, sulfur-containing urea is a supplementary, upgraded variety of ordinary urea; choosing it sensibly according to soil conditions and crop needs can better bring out the fertilizer effect of combined nitrogen and sulfur.