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