Effects of chemical fertilizers application combined with manure on ammonia volatilization and rice yield in red paddy soil

A field experiment was conducted in Qiyang, Hunan province, a typical red soil region of southern China, to study the effects of organic and inorganic N fertilizers on ammonia volatilization and rice yield in paddy soil. Four treatments were designed with four replications and laid out in field by Latin Square Design. Four treatments were PK treatment as control, NPK treatment (urea as N), NPKM treatment (half chemical fertilizers + half manure) , M treatment (pig manure as N) , same amount of N, P, K either organic or inorganic forms (N 150 kg/hm2, P2O5 100.5 kg/hm2 and K2O 109.5 kg/hm2) were applied in each plot. All fertilizers were applied once as base fertilizers before one day of rice transplanted. NH3 volatilization was measured by chamber method. Concentration of NH4+-N, pH and temperature in surface water were determined simultaneously. The results showed that NH3 volatilization in the four treatments decreased in order as NPK NPKM MPK. N loss through NH3 volatilization during rice growth period accounted for 37.8 % of N applied in NKP treatment, 12.7% in NPKM treatment and 0.9% in M treatment averagely. When urea was applied to paddy soil, it changed to NH4+-N quickly, the concentration of NH4+-N in surface water within 10-15 days after fertilization was much higher than that of manure treatment. NH3 volatilization, which was mainly occurred in 20 days after fertilization in early rice and 9-10 days in later rice, was close related to concentration of NH4+-N, temperature and pH of surface water. The rice yields of NPKM, NPK, M treatments were increased by 68.6%,68.1% and 60.0% respectively for early rice, and increased by 72.0%,69.6% and 34.2% for late rice compared with control treatment. Not only the yield of rice with NPKM treatment increased by 70 % averagely compared with PK treatment, but also thenitrogen loss was less compared with NPK treatment. N use efficiency of NPKM treatment was 34.9% , higher than that of NPK treatment (33.2%) and M treatment (28.0%).