| Based on the sulfur coated urea and sulfur coating as the main materials, studies of different dosage of sulfur coated urea content and various sulfur coated urea on rice growth effect were carried out in this paper. And we studied the influence of the different dosage of sulfur coating to the chemical properties of the soil and rice growth and yield after years of sulfur coated urea employ on the basis of common urea and sulfur coated urea. This paper presented warning to the sulfur coating residual problems of SCU and presented the reasonable application of SCU on rice. Main research results and conclusions were as follows:1. The nitrogen utilization and the yield of rice were increased remarkably through different dosages of sulfur coated urea and different fertilization modes. With an increase in the amount of sulfur coated urea, the rice yield increased significantly. And SCU3 (high quantity controlled release fertilizer) had the highest yield, with production increases of 95.46% and 26.58% compared with common urea nitrogen and comparison, respectively.2. Different amount of sulfur coating brought different influences to rice growth and chemical properties of soil. Compared with CK, all nitrogen treatments had good effects of yield. While compared with common urea, low sulfur amount resulted better yield. But with increasing of the amount of sulfur coating, the rice yield had decreasing trend. Hence, proper amount sulfur could improve the yield of rice while excessive sulfur caused a reduction of output.3. Compared with CK, the contents of water-soluble HCO3- dealed with nitrogen reduced, and the content of soil water-soluble Cl- increased significantly. While compared with CK and Urea treatment, all the sulfur treatment significantly increased the contents of water-soluble SO42- in soil. Proper amount of sulfur coating could improve activation degree of Ca, Mg in soil, while excessive amount of sulfur coating could inhibit its activation.4. The sulfur coating was applied based on the sulfur coated urea, and different amount of sulfur coating brought different influences. Proper amount of sulfur coating had significantly promotive role to rice plant height, chlorophyll, growth and yield of rice. Compared with CK, the increase production of the rice yield was more than 60% by using controlled release fertilizer, and the SCU + 5S had the highest rice yield. Different amount of sulfur coating had a little effect to nitrogen utilization of rice.5. The sulfur coating was applied based on the sulfur coated urea, could improve the content of soil soluble salt, resulting in hoist of conductivity. In the flooded conditions, high amount of sulfur coating was reduced, lead to large amount of H2S, Fe2+ and Mn2+. As a result, the soil reductive material volume was increasing rapidly. And the original soil redox system was changed. The acid-base balance of soil was also affected and the physical and chemical properties of soil were degenerated, leading to soil acidification and reducing.6. In flooded conditions, low sulfur coating could improve the growth of microorganism and microbial activity. On the contrary, high amount of sulfur coating was reduced to sulfide (S2-), inhibiting the growth of microorganism and microbial activity. The soil microorganism quantity (SMBC and SMBN) increased firstly, and then decreased with the increased amount of sulfur coating.The application of sulfur coated urea at one time instead of traditional ordinary urea method could satisfy the needs of rice growing season, and had a significant effect of nitrogen utilization and the yield of rice. Under flooded conditions, controlled release fertilizer application for successive years had potential threat to the deepen soil acidification reducibility. Therefore, in the actual rice production, we should adopt appropriate draining fell, reduce groundwater, and implement measures such as floods rotation to enhance oxidizability, eliminate reducing material and improve the growth of rice. |
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