Effect of Nitrogen Application Level on Nitrogen Use Efficiency in Wheat and Soil Nitrate-N Content under Bed Planting Condition

Abstract

The variation of nitrate-N content in soil was investigated in winter wheat under bed planting,and the N use efficiency and yield were compared between cultivation patterns of bed planting and flat planting.The amount of N accumulation in wheat plant,N harvest index,and grain yield of wheat were increased with the increase of N application rate,but the N use efficiency and the soil N contribution tended to decrease.At low N application rate(0-66 kg ha-1),the possibility of nitrate-N leaching was declined with no massive accumulation at 0-100 cm soil layer.At high N application rate(165-264 kg ha-1),the content of nitrate-N in 60-100 cm soil layer increased and began to move down in the soil.Cultivation patterns had an effect on N use efficiency,which of bed planting showed higher N use efficiency and wheat yield than flat planting.In flat planting pattern,nitrate-N was mostly accumulated in soil of 60-80 cm depth,which was shallower than that in flat planting(80-100 cm).Cultivation patterns had larger effect on N use efficiency than N application rate;whereas,N application had larger effect on N harvest index,grain yield,and harvest index than cultivation patterns.Under the experimental condition,high N use efficiency and N harvest index were observed in N application treatment of 165 kg ha-1,and the N use efficiency of wheat was significantly higher in bed planting(45.32-47.25%) than in flat planting(35.75-36.41%).The highest grain yields were 8 078.31 kg ha-1 in flat planting and 8 212.27 kg ha-1 in bed planting,which were both obtained in N application treatment of 264 kg ha-1.