Effects of nitrogen fertilizer combined with nitrification inhibitor on growth and N₂O emission of fresh maize in Hainan

【Objective】In order to provide theoretical basis for guiding the one-time base application of nitrogen fertilizer and reducing N₂O emission in the production of fresh maize in Hainan，the effects of nitrogen fertilizer combined with nitrification inhibitor dicyandiamide（DCD）on the growth and N₂O emission of fresh maize were studied.【Method】Sunuo No. 6 maize was selected as test material，and a field plot experiment was conducted. There are 4 treatments including control（CK，no urea applied），one-time base application of nitrogen fertilizer（S1，urea+DCD），two-time application of nitrogen fertilizer（S2，urea applied at 40% base，60% urea applied at large trumpet stage）and three-time application of nitrogen fertilizer（S3，urea applied at 20% base，40% urea was applied in the small trumpet stage，40% urea was applied in the tasseling stage）. The N₂O gas was collected at the 2^nd，5^th and 8^th d after fertilization，and collected once each week later to determine the soil N₂O emission flux and cumulative emission，soil samples were collected before fertilization and during gas extraction to determine soil pH and other chemical properties，plant biomass，yield and nitrogen use efficiency were determined during maize harvesting.【Result】There was no significant difference between soil pH of nitrogen application treatment and CK（P>0.05，the same below），but soil pH of S1 treatment was the lowest and significantly lower than that of S2 treatment（P<0.05，the same below）. Compared with S2 and S3 treatments，S1 treatment significantly reduced soil total nitrogen content by 6.15% and 12.86% respectively. S1 treatment was beneficial to increase soil available P content， but not conducive to the accumulation of available potassium，S2 and S3 treatment has no significant effect on soil available phosphorus and available potassium content. Nitrogen application significantly increased maize plant biomass and yield，both values in S1 treatment were the highest. Compared with S2 and S3 treatments，S1 treatment significantly increased maize plant biomass by 30.42% and 10.95%，and yield significantly increased by 13.37% and 19.05% respectively. The nitrogen efficiency of S1 treatment was the highest，which was significantly increased by 37.00% and 59.38% compared with S2 and S3 treatment respectively. Nitrogen application significantly increased nitrogen content in maize organs. The cumulative nitrogen uptake of maize plants under S1 treatment was 22.95% and 34.69% higher than that under S2 and S3 treatment respectively. S1 and S3 treatments were beneficial for nitrogen distribution to stems and leaves，but S2 treatments did not change the way of nitrogen distribution. Nitrogen application promoted N₂O emission，and the cumulative N₂O emission of all nitrogen application treatments was significantly higher than that of CK，and the highest N₂O emission was found in S2 treatment，which decreased by 54.46% and 54.33% in S1 and S3 treatments respectively，compared with S2 treatment. The HN₄⁺-N content of soil in each treatment had an obvious peak from the trumpet stage to the harvest stage，while the peak time of NO₃^--N content in soil was different. Correlation analysis results showed that N₂O emission flux was extremely significantly and positively correlated with NO₃^--N content and soil water content（P<0.01， the same below），and extremely significantly and negatively correlated with 5 cm soil temperature.【Conclusion】Compared with multiple nitrogen application，nitrogen fertilizer combined with nitrification inhibitor one-time base application can significantly promote the fresh maize growth，yield，nitrogen efficiency and also reduce N₂O emission at the same time. It can be used as the recommended fertilization mode for fresh maize in Hainan.