Effects of Water and Nitrogen Coupling on Soil Gaseous Nitrogen Emission Under Alternate Irrigation & N Placement

A field experiment was conducted by second-order central designed with composite orthogonal rotational matrix for two variables to investigate the effects of quantity coupling between water and N under AINP(alternate irrigation and N Placement) on soil NH3 volatilization and N2O emission and summer maize yield.The gaseous N was collected by open-bottomed chambers made from PVC in field.NH3 was absorbed in the chamber with boric acid and then titrated with dilution H2SO4 in the lab.A 5mL sample of headspace air was taken at 2-4 d interval after fertilization and stored in evacuated glass vials with butyl rubber seals which were put in 4℃ fridge until analysis.The N2O concentration of each sample was measured by Varian 3800 gas chromatograph.The results indicated that total NH3-N volatilization accumulation of AINP were 4.78-17.00 kg/hm2,and 1.89%-11.89% of applied N,while soil N2O-N emission were 0.59-0.88 kg/hm2,and 0.01%-0.31% of applied N.Total NH3-N volatilization and N2O-N emission from conventional treatment were 19.55 kg/hm2 and 1.29 kg/hm2,and 8.27% and 0.45% of applied N respectively.Maize yield of AINP were 4 163.18-6 942.00 kg/hm2.The simulation results showed that the lowest of total NH3-N volatilization and N2O-N emission would be 9.28 kg/hm2 when water amount was 800.00 m3/hm2 and N rate was 24.80 kg/hm2.The highest maize yield would be 6 367.07 kg/hm2 when optimal water amount and N ratio were 930.12 m3/hm2 and 238.19 kg/hm2 respectively.The NH3 volatilization and N2O emission could be lower(≤12.84 kg/hm2) when irrigation water were 658.06-941.94 m3/hm2 and N rate were 87.36-131.16 kg/hm2.The maize yield could be higher(≥4 934.91 kg/hm2) when the water amount were 910.22-1 134.20 m3/hm2 and N rate were 215.89-270.78 kg/hm2.Under AINP,there could be not only lower the gaseous N loss but also higher yield when the optimal irrigation water were 910.22-941.94 m3/hm2,but there was no agreement of the N rate between higher yield treat and the lower N loss one.Compared with conventional irrigation and N application,AINP could decrease NH3 volatilization and N2O emission and increase summer maize yield significantly.