Urea, a white crystalline solid containing 46% nitrogen, is widely used in the agricultural industry as an animal feed additive and fertilizer. Commercially, fertilizer urea can be purchased as prills or as a granulated material. In the past, it was usually produced by dropping liquid urea from a “prilling tower” while drying the product. The prills formed a smaller and softer substance than other materials commonly used in fertilizer blends. Today, though, considerable urea is manufactured as granules. Granules are larger, harder, and more resistant to moisture. As a result, granulated urea has become a more suitable material for fertilizer blends.
Water-soluble fertilizers may be coated or encapsulated in sulfur to slow the release of nutrients. Sulfur-coated urea (SCU) is manufactured by coating hot urea with molten sulfur and sealing with polyethylene oil or a microcrystalline wax. It usually contains 30-40%N and 15-20%S and the colour of Sulfur-coated urea is yellow.
It is being used in rice, wheat, corn, vegetable, bamboo, fruit and garden with such features as fertilizer-saving, labor-saving, output-increasing, income-increasing and environment improvement. As one new kind of bio-fertilizer, it has excellent social and economic benefits. Demand for SCU has increased over time because of the following advantages relative to readily soluble nitrogen fertilizers:
- In have rain condition, the nitrogen loss per mu (15kg nitrogen) is 0.53~0.6kg, which is similar to the land without nitrogen, which the normal loss is 2.13~2.4kg/hectare. In the regions where lose nitrogen easily, the availability is 50% (4% for normal urea) in lands.
- It can improve outputs of crops all kinds of lands.
|Average Degree %||15.7||15.4||13.4||14.9||14.7||8.5||25.9||5.9|
|Increase Degree %||5.0-57.0||5.5- 38.1||4.3-39.0||3.5-39.1||6.4- 32.9||5.0-13.8||14.9-36.9||5.0-13.0|
Sulfur coated urea can offer good effects for ropes with long growth period, crop in sand lands. It also offers good effects to green lands, pasturage and ornamental.
- Improving the quality of crops.
Sulfur coated urea can improve the quality of crops, which is related to the demands of plant on sulfur and the dosage of fertilizer.
- Used as soil regulator.
After the urea is release, the sulfur shell can keep moisture air and increase the permeability of soil, it also can kill bacteria and dispel insects. It also can improve soil in long-term application.
- Saving labor and time, reducing the coat of labors.
It can meet the demands of growth in one-time application. As to the crops with long growth period such sugar cane, can offer fertilizer in every stage of growth; moreover, it is hard to fertilize in the strawberry field coated with membrane, so we can used SCU for the crops coated with membrane, especially for chili and tomato in green house.
Polymer-coated urea fertilizers use a hydrophobic (water insoluble) coating that temporarily isolates the urea prill from the soil environment. These polymer coatings may be resins or mineral-based products that act as semipermeable membranes or impermeable membranes with tiny pores. Nutrient release through these membranes is controlled by the properties of the coating material, i.e., its permeability characteristics as affected by temperature and moisture Thus, they are not significantly affected by soil properties such as pH, salinity, soil texture, microbial activity, re-dox potential or cation exchange capacity.