| With industrialization and application of Slow-Release and Controlled-Release Fertilizer, Sulfur Coated Urea (SCU) has played an important role in fertilizer markets because of its lower price. But sulfur occupies 15%～30% in SCU. SCU brings a lot of sulfur to soil which is oxidized to sulphuric acid that may affect soil environment and plants growing. Bag buried and lab cultivation experiments were conducted to study degradatioin rate of sulfur-coating residue and capacity of SO42- absorption of different soil, in order to tentatively judge feasibility of using SCU in a long term. Pots experiments were conducted with maize and rice in brown soil and moisture soil, in order to study effects of SCU on soil chemical properties, biological properties and crops' physiological properties with different soil and farming methods, which will guide long-term utilization of SCU. The main results are as follows:1. Sulfur coating could stay in soil after brought in, and was oxidized to SO42- by soil bacteria. But brown soil and moisture soil have strong capacity of absorbing SO42- that can reduce water-solution SO42- to a certain degree and reduce effects to soil and crops.2. During maize growth period, SCU increased available sulfur significantly. On paddy fields, available sulfur had nearly the same change trends to dry fields.3. SCU increased water-solution SO42- in soil significantly. But with different soil and cultivation methods, it had different effects on pH of soil. When planting maize on Brown soil, soil pH didn't bring down significantly at harvest stage for successive two years. When planting maize on Chao soil, soil pH of each treatment was lower at harvest stage than that of before planting. But sulfur coating didn't have significant effects on paddy fields.4. When planting maize on brown soil and moisture soil, soil EC was brought up significantly at jointing stage, tasseling stage and harvest stage of maize by high SCU. But in paddy fields, it had different situation, and soil EC was the highest at harvest stage of rice.5. SCU brought up soil available Fe, Mn and Cu in moisture soil because pH was brought down by it.6. SCU brought up quantity of sulfur bacteria and dessulphurizing bacteria. Quantity of soil sulfur bacteria in SCU treatments was higher than that of common urea treatments at jointing stage and harvest stage of maize. And quantity of dessulphurizing bacteria increased significantly at jointing stage, heading stage and harvest stage of rice.7. In this experiment, fertilizer had retarding effect on catalase, and the effect growing with increase of fertilizer. In brown soil, SCU had anxo-action to catalase because it could release fertilizer slowly. But SCU didn't take on the same effect on moisture soil. When planting rice in brown soil, catalase had different change trends to that of dry fields. After inundation, catalase activity of nearly every treatment brought up gradually.8. SCU did not increase SO42- in shelled maize. SCU increased chlorophyll, height and yield of maize with two different soil. But sulfur coating had no significant effect on increasing chlorophyll and height, and sustained nitrogen supplying was the main reason. With low nitrogen, sulfur coating had good effect on increasing yield of maize, but with high nitrogen, controlled-releasing played the most important role. Yield of maize was highest in 2 times fertilizer. Compared with urea treatments, grain yield of SCU treatments increased 10.19% and 10.94% in brown soil, and 21.37% and 11.89% in moisture soil within two years. SCU had no significant effects on chlorophyll and height of rice, but increased tillter number and yield significantly. With different fertilizer levels, yield of rice increased 26.68% and 8.93% in 2008, and increased 7.02% and 9.72% in 2009.
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