Studies On The Techniques For Controlling Nutrient Runoff Losses From Rice Fields And Soil Erosion From Nonwood Forests

Runoff losses of nitrogen and phosphorus from cropping systems are main non-point pollution sources. Soil erosion in economic forests is also serious. Controlling nutrient imports and runoff is important measurement for lowering nitrogen and phosphorus loads.In this paper, the effects of the integrated fertilization with organic manure and chemical nitrogen fertilizer, or the application of coated urea on rice growth and nitrogen and phosphorus runoff losses were studied. The effects of vegetation management on soil erosion and nutrient losses in chinese chestnut forest were also abserved. The results were as follows:1. Under rice-rice cropping conditions, the grain yields of early rice or late rice of the treatment of integrated fertilizion with organic manure and chemical nitrogen fertilizer were similar to those of the chemical fertilizion treatment (FP). So were the amounts of nitrogen and phosphorus accumulated in shoots of early rice or late rice. The appearant chemical nitrogen recoveries in late rice of the integrated fertilizion treatments (CM, CM-N) were significantly higher than that of FP treatment. Integrated fertilizion with organic manure and chemical fertilizers can maintain rice grain yields and improve nitrogen use efficiency in late rice or the whole rice-rice rotation.2. Under single-season rice cropping conditions, the grian yield and nitrogen amount accumulated in rice shoots of the treatment of integrated fertilizion with organic manure and chemical fertilizers treatment (T4) based on reducing 30% nitrogen dose and 40% phosphate dose were significantly higher than those of the control (T1).Concentrations and lossed amounts of total nitrogen, total phosphorus, ammonium nitrogen, organic nitrogen, inorganic phosphorus of treatment T4 in runoff water were significantly lower than those of treatment T1. As the differences of runoff volumes among four treatments were unsignificant, the reduction of nitrogen and phosphorus losses was contributed to the lower nitrogen and phosphorus concentations in runoff water for the intergrated fertilizion.3. Under single-season rice cropping conditions, the grain yield of the treatment (T4)with applying coated urea based on reducing 30% nitrogen dose and 40% phosphate dose was similar to that of the control (T1), and so were the amounts of nittogen and phosphorus accumulated in rice shoots. Concentrations and lossed amounts of total nitrogen, total phosphorus, ammonium nitrogen, organic nitrogen, inorganic phosphorus of treatment T4 in runoff water were significantly lower than those of treatment T1. Since the differences of runoff volumes among five treatments were unsignificant, the reduction of nitrogen and phosphorus losses was due to the lower nitrogen and phosphorus concentations in runoff water for the application of coated urea.4. In the two field experiments with single-season rice, the concentrations of total nitrogen, ammonium nitrogen, nitrate nitrogen, total phosphorus and inorganic phosphorus in runoff water were significantly correlated to the contents of water-soluble total nitrogen, ammonium nitrogen, nitrate nitrogen, total phosphorus and inorganic phosphorus in soil, implying that soil soluble nitrogen and phosphorus were the main sources of nitrogen and phosphorus in runoff water. The reduction of fertilizer rates and utilization of the slow release fertilizer can effectively lower the runoff losses of nitrogen and phosphorus from rice field.5. The volume of runoff water and amount of sediment of treatments (T3, T4, T5)with bandyly planting of bamboo in chinese chestnut forest were significantly lower than those of the control (T1). The differences of concentrations of total nitrogen and ammonium nitrogen in runoff water and concentrations of total nitrogen and total phosphorus in sediment among treatment T1, T3, T4 were unsignificant. The losses of total nitrogen, ammonium nitrogen, nitrate nitrogen, total phosphorus, inorganic phosphorus with runoff water and total nitrogen and total phosphorus with sediment of treatment T4 were significantly lower than those of treatment T1, which were due to the reduction of runoff water and sediment.