NBPT (n-butyl thiophosphoryltriamide) and DMPP (3

4-dimethylpyrazolphosphate) were used as composite inhibitors. By optimizing the combination and using the drum spray process

a new type of composite inhibitor coated urea fertilizer was developed. The effect of coating was analyzed by SEM and EDS. Field experiments were conducted to systematically evaluate the effects of different nitrogen topdressing on nitrogen regulation. Five treatments were set up: (1) No N application (CK); (2) farmers’ habit of applying urea (CU); (3) optimization of applying urea (CUU); (4) optimization of applying inhibitor coated urea (CUY1); (5) optimization of applying inhibitor coated urea (CUY2). The field in-situ continuous dynamic observation was carried out within 15 days after applying urea at the ten leaf stage of summer maize and jointing stage of winter wheat. The composite inhibitor was uniformly coated on the surface of urea to form a thin

compact and smooth coating layer. The coating layer was evenly distributed with phosphorus and sulfur elements

which indicated that the composite inhibitor and urea had effectively combined. Compared with the common urea after the same N application

the ammonia volatilization of CUY1 and CUY2 in summer maize and winter wheat decreased by 55.19%

32.15% and 52.46%

39.43% respectively. After topdressing in summer maize season

the content of soil NO3--N in 0-20 cm soil lager in CU and CUU treatment reached the peak value at the 5th day

which was significantly higher than that of CUY1 and CUY2 treatment at the same period

and significantly lower than that of CUY1 and CUY2 treatment at the later stage. According to the trend of CUY1 treatment

the effect of CUY2 treatment on stabilizing NO3--N in 0-20 cm soil layer is better. After topdressing in winter wheat season

the content of soil NO3--N in CU and CUU treatment reached the peak value on the 5th and 3rd day

respectively. The content of soil NO3--N in CUY1 and CUY2 treatment increased slowly

and reached the peak value on the 11th day

which was 38.64%

36.08% and 43.65%

48.19% respectively lower than that of CU and CUU treatment. After the 11th day

the content of NO3--N was significantly higher than that of CUU with the same N application. At the same time of ensuring the yield and net income

urea coated with inhibitor significantly reduced the ammonia volatilization and leaching loss concentration of nitrogen

among which CUY1 treatment on winter wheat had better economic benefit

CUY2 on summer maize had the best effect of regulating nitrogen

and the effect of reducing leaching down was obvious.