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The Research On Ammonia Volatilization And Nitrogen Use Efficiency In Saline-sodic Paddy Fields

Posted on:2018-03-04Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y Y LiFull Text:PDF
GTID:1313330539465096Subject:Ecology
Abstract/Summary:PDF Full Text Request
Nitrogen concentration is very low and soil fertility is poor in the saline-alkali soil in the Songnen Plain of Northeast China.Soil salinity and nitrogen concentration significantly influence rice yield and nitrogen use efficiency.However,it was very difficult to improve nitrogen use efficiency in saline-sodic paddy fields.The purpose of our experiment study was that reveal the relationship of environmental factors and ammonia volatilization in saline-sodic soils under different nitrogen fertilizer application levels,nitrogen migration and nitrogen use efficiency,nitrogen absorption regularity of rice and the relationship between rice root activity and yield were also studied by 15N-labeled stability urea in saline-sodic soils.The research results were as follows:1.The simulation test in the laboratory shows that,nitrogen volatilization increased with the pH rising when the pH in solution was from 7.59 to 8.55.The nitrogen volatilization maximum occurred in pH 8.55.The nitrogen volatilization of 3 nitrogen fertilizers was in the order: ammonium sulfate > ammonium nitrate > urea,with the pH changing from 8.55 to 9.58.The nitrogen volatilization of urea increased with the EC rising.2.In a pot experiment,we found that the ammonia volatilization in moderate saline-sodic soil was significantly greater than the amount of ammonia volatilization in light saline-sodic soil.The amount of ammonia volatilization significantly increased with increasing of nitrogen fertilizer application.It was positive correlation between these two indexes.In the long term location fertilization experiment,combined application of organic fertilizer and NPK and straw returning can decrease the amount of ammonia volatilization in saline-sodic paddy fields.3.In field trials,rice vegetative growth and reproductive growth were significantly inhibited in saline-sodic soil.When the soil pH was 9.0,the rice seed setting rate was around 40%.The aboveground growth of rice was affected mainly by saline-sodic stress in soil.Under the same degree of salinity,reasonable application of nitrogen fertilizer can significantly promote the rice growth and increase rice yield,and decrease the negative effect of salinity on rice growth.4.With increasing of nitrogen application levels,the output of bleeding sap increased significantly in rice root.And the output of rice bleeding sap was the largest and the grain yield was also the highest during rice heading stage in saline-sodic soils.5.At the same saline-sodic degree,nitrogen requirement were different for different varieties rice,the yield dongdao 4 rice,dongdao 2 rice and Baijing 1 rice reached the highest when nitrogen application level was 150 kg·N/hm2;the yield of Changbai 9 rice reached the highest when nitrogen application level was 300 kg·N/hm2.Therefore,the optimal N application rate should be determined according to the degree of soil salinity and the characteristics of rice varieties in rice production.6.Different nitrogen use efficiency existed the rice plant in varies saline-sodic soils.In light saline-sodic soil,with nitrogen application rate increasing from 75 kg·N/hm2 to 300 kg·N/hm2,nitrogen recovery efficiency in rice plant changed from 46.75% to 62.95%.In moderate saline-sodic soil,with nitrogen application rate increasing from 75 kg·N/hm2 to 300 kg·N/hm2,nitrogen recovery efficiency in rice plant changed from 39.84% to 48.21%.The 15 N retention rate changed from 4.1% to 10.0% in two saline-sodic soils.7.The soil nitrogen balance was calculated as the basis of nitrogen,the optimal nitrogen application rate was calculated by nitrogen regression index method in field scale,and obtained the calculation formula of nitrogen application rate under straw returning in saline-sodic paddy field,it was: RNR = 1.267×10-6Yyield2 + 1.24×10-2Yyield-41.4;If without straw returning,the calculation formula was: RNR = 1.267×10-6Yyield 2 + 1.24×10-2Yyield-22.7...
Keywords/Search Tags:Saline-sodic soil, Rice, Nitrogen uptake, Ammonia volatilization, Nitrogen use efficiency
PDF Full Text Request
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