[Emission of NH3 and N2O from Spinach Field Treated with Different Fertilizers].

Agricultural management techniques such as fertilizer or manure application have substantial influence on NH3 and N2O emissions and, by understanding this influence, management strategies can be developed to reduce them. An experiment was conducted in a greenhouse at Hunan Agricultural University during 2012 to 2013, to investigate effects of different fertilizers on NH3 and N2O emissions. The treatments included control without fertilizer (CK), swine composting fertilizer (SC), stored swine manure fertilizer (SS), and chemical fertilizer (FC). The fluxes of NH3 and N2O were collected by venting method and static-chamber method, respectively. The results showed that during the spinach growth season, compared with FC, loss of both NH3 and N2O for SC were reduced by 52.9% and 95.12%, respectively(P<0.01). However, loss of NH3 for SS increased by 24.8%, and loss of N2O reduced by 48.8% compared with FC. Loss rate of NH3 were SS (10.97%) > FC (4.19%) > SC(2.74%), and emission coefficient for N2O were FC(4.50%) > SC(2.21%) > SS(0.60%). Yield and utilization of nitrogen for SC were reduced by 19.61% and 13.20% compared with FC, respectively, but not significantly; and significantly reduced by 27.9% and 40.0% compared with SS, respectively. Loss of gases (NH3 and N2O) for SC were 1.83%, which was the lowest, while utilization of nitrogen for SC was 13.20%, similar with FC. Greenhouse temperature was not the critical factor during the spinach planting in winter, but soil water was. Therefore, optimizing manure management could reduce ammonia volatilization and N2O emission loss without decreasing vegetables production, and the present data indicated that SC would be optimal for better yields with reduced ammonia volatilization and N2O emission loss.

[Emissions of NH3, N2O, and NO from swine manure solid storage in winter].

Swine manure solid storage is a typical management in rural area of China. In order to investigate the characteristics of NH3, N2O and NO emissions during manure storage in winter (Nov., 2012 to Feb., 2013), two treatments were conducted: non-covered (NC) and covered (C) with straws, and each treatment had three times of pile-turning during the 73 days storage. The emission fluxes of three nitrogen gases (NH3, N2O and NO) were measured and the profile-N2O concentrations inside the swine pile profile and in the soil under the pile were also measured. The results indicated that 2.1%-2.6%, 0.02% and -0.000 25% of total nitrogen were lost in the form of NH3, N2O and NO respectively during the whole swine manure solid storage. The nitrogen gases in the two treatments had the same variation characteristics, but all the nitrogen gases were reduced in the covered treatment. In the early storage stage, NH3 emission peak occurred first and then the emissions of N2O and NO started increasing. In the middle storage stage, the emissions of NH3 and NO showed mutual growth and decline trend. In the late storage stage, N2O emission peak was twice higher than that in the early stage, while NH3 and NO emissions showed a slight increase. Before and after pile-turning operation, NH3 emission had little change, but N2O emission was decreasing and NO emission was rising after pile-turning.

[Performance of nitrogen and phosphorus removal of sulfur/limestone autotrophic denitrification system].

In order to investigate the performance of nitrogen and phosphorus removal of the sulfur/limestone system from low C/N municipal sewage, a sulfur/limestone packed column reactor fed with synthetic wastewater, and operated in the way of anaerobic biological filter was constructed. The effects of HRT, initial concentration of phosphate, pH and temperature on nitrogen and phosphorus removal were studied. The results showed that with influent of NO3(-) -N 30 mg/L, PO4(3-) -P 15 mg/L, the optimal HRT value was 6 h, and removal rates of TN and phosphorus were 100% and 44.64% respectively. Initial concentration of phosphate and initial pH had a significant influence on nitrogen and phosphorus removal. In order to keep nitrogen removal rate higher than 90%, initial concentration of phosphate should not be below 0.4 mg/L; the optimal pH value was 6.5, and removal rates of TN and phosphorus were 91.51% and 47.68% respectively. Temperature had a positive impact on that system, the nitrogen and phosphorus removal rate decreased with decreasing temperature. The nitrate removal efficiency was high in the temperature range of 18-30 degrees C, and the efficiency of phosphorus removal rate reached about 50%, when the temperature was between 25-30 degrees C. The dephosphorization behavior of sulfur/ limestone system correlated closely with autotrophic denitrification process, and the mechanism of phosphate removal of the SLAD system was mainly due to chemical precipitation. The system had the performance of nitrogen and phosphorus removal from low C/N municipal sewage, the highest phosphorus removal rate could reach 50%.