Utilization of Nitrogen in Wastewater Low in Pollution Degree in Paddy Fields and Its Effect on Reducing Fertilizer Application in Tai Lake Region

A pot experiment was designed to study the potential capacity of paddy fields in reducing fertilizer application rates with the irrigation of 3 kinds of low-polluted wastewater: eutrophied river water (RW), tail water from a domestic sewage treatment plant (DS) and biogas slurry (BS), as well as the effects on the growth and yield of Oryza sativa, N uptake, N loss in field runoff, ammonia volatilization, soil nutrients. Results show that 1) in Treatments BS, DS and RW, the plants all grew normally and yield of the crop was not affected with a higher N uptake efficiency. 2)Compared to Treatment SF (irrigated with tap water), Treatments BS, DS and RW were 21.6%-48.2% lower in concentration of total N in the overlaying surface water during the peiord before tillering. N concentration was more or less the same during the tillering period, and much higher during the panicle fertilization period and the milking period. 3) Treatments BS, DS and RW reduced the daily mean N volatilization during the basal and panicle fertilization periods, but increased the rate during the tillering and milking periods. However, the total ammonia volatilization of the whole growing season did not vary much between treatments and ranged from 41.58 to 45.45 kg·hm^-2. 4) Soil available N, P, K and organic carbon after harvesting was a bit higher in Treatments BS, DS and RW than in Treatment SF, especially in Treatment DS. 5)Throughout the whole rice growing season, the paddy field could accommodate 4858-5441 m³·hm^-2 for low polluted water. Treatment DS, RW, and BS removed 107.1, 31.4 and 132.9 kg·hm^-2, respectively, and could reduce the use of chemical N fertilizer by 44.41%, 12.83% and 55.11%, respectively. In terms of integrated yield and environmental benefits, Treatment DS significantly increased N fertilizer utilization rate and minimize the risk of N loss with runoff during the early rice growing season, and improved effectiveness of soil fertility of the paddy fields in the Tai Lake Region.