Effects Of N Application Rate On Yield Of Maize And NO3~--N Content Of Soil In Sichuan Hills Region

From2010to2011years, in this paper, the field experiments of5different levels of nitrogen were conducted at Renshou and Nongchang in Sichuan, to focus on effects of nitrogen rate on dry matter accumulation, N accumulation and soil NO3--N content at different growth stages of maize and yield, nitrogen use efficiency and residual nitrogen in the different position of soil profile after harvest. The results showed us:(1)In the range of300kg/hm2nitrogen rate, with the increasing of nitrogen rate, the yield improved, but added more, the yield increased unsignificantly or decreased. At Renshou and Nongchang, the yields of N300application were more than others, which were9360and8885kg/hm2, and increased117.75%,145.69%than No in2010. The yield of N390application was highest and increased129.4%than No and not obviously compared to N195and N292.5, which was7284kg/hm2. With the increasing of nitrogen rate, row number per ear, grain number per row and1000-seeds weight increased at every stage.(2)The aboveground biomass and N accumulation of maize increased gradually as growth process at different nitrogen amount, and the upward trend of aboveground biomass was consistent at Renshou(2010) and Nongchang(2010and2011). In2010, the aboveground biomass and N accumulation of maize on different level of nitrogen was not significantly different at Renshou, but for Nongchang it was not. And N accumulation of other opptiongs was increased contrasting to No at every growth stage. The aboveground biomass of N300application was highest after harvest at both Renshou and Nongchang. At Nongchang, N accumulation of maize in the different nitrogen rate increased greatly, the N accumulation of N390application was highest, increased by404.8%than No opption. In2011, the aboveground biomass of N195application was highest at every growth stage except for harvest. But when was harvest stage, the aboveground biomass of N390opption was highest, but the difference was not obvious that compared to N292.5application. Plant height and leaf area index along with the increase of nitrogen rate amounts, had increased in the period.(3)In2010, the PFP-N of N150application was higher than others, respectively, were53.9and39.7kg/kg at Renshou and Nongchang. But for Nongchang was N97.5application and it was71.2kg/kg in2011. Under the treatments of N150and N97.5, the NRE, NAE and NPE were higher than other treatments.(4)With growth process, the trend of rhizosphere soil content was drop-rising-descending, and the difference was not significant for each other, but the biger nitrogen levels was more than other treatments at Renshou and Nongchang in2010. At Renshou, soil NO3--N content changed as "U". Soil profile NO3--N residue of0-40cm was more than others and soil profile NO3--N residue is highest in the N375treatment at Renshou and Nongchang, but for Nongchang, the total NO3--N residue was less than Renshou.In2011, soil profile NO3--N residue of0-40cm was rising-drop-drop trend and was more than other layer. The soil profile NO3--N residue of N390treatment was highest.