Effects Of Dicyandiamile And Different Fertilizer Levels On Nitrogen Distribution And N₂O Emissions In Grain System

Nitrogen is an essential element for plant growth. The excess of the crop nitrateaccumulation, nitrogen leaching and runoff losses from arable land, increasing ofatmospheric N₂O emission flux because of excessive nitrogen application andunreasonable management measures to achieve high yield have caused a worldwideenvironmental concern.To reduce the amount of soil N₂O emission flux into theatmosphere, we discuss nitrification inhibitor to control urea hydrolysis and oxidationprocess of NH4+. It plays an important role in controlling nitrogen fertilizer pollution andenhancing the nitrogen use efficiency. Using typical aquic soil for the tested soil,we carriedout corn-wheat-corn rotation experiment for three seasons. Different fertilizer levels addedto nitrification inhibitor Dicyanamide （DCD） to study the effects of nitrification inhibitorDicyanamide （DCD） and different fertilizer levels on nitrogen use efficiency, soil Ndistribution in time-space and N₂O emission flux.We could determine the optimal nitrogenfertilizer amount. It was proved that adding nitrification inhibitors DCD effected onreducing N₂O emission flux.These were very important to provide scientific theory supportfor reasonable fertilization amount, improving nitrogen use efficiency and reducing thepollution of the agricultural.The main conclusions of this study were as following:1. To determine the reasonable amount of nitrogen fertilizer and nitrificationinhibitors. The results showed that during the three seasons, with the increasing of nitrogenapplication rate, the plant dry weight and grain of maize and wheat were increasing as “S”shape in every season. When nitrogen application rate was at225kg·hm^-2, the yields ofmaize and wheat were the highest. With DCD or without DCD treatments both had a twoquadratic regression between the application rate and yield.The quadratic regression modelcould calculate the maximum yield application rate of corn and wheat in every season.Compared with the blank treatments, the yields of nitrogen treatments in the three seasonswere increased by24.42%-32.89%. Compared with LN, MN and HN treatments, the yieldsof DCD+LN, DCD+MN, DCD+HN treatments in the three seasons were increased by2.71%,0.37%and1.78%. It suggested that DCD could improve the crop yields, because ofthe reinforcement of dry matter accumulation and nitrogen nutrient use efficiency andprocess.2. To definite the temporal-spatial distribution discipline of the nitrate content in soil in every season. The nitrate content in soil straightly reduced with the soil depth in thevertical distribution, especially in0⁴0cm soil. As the extension of crop growth period,the nitrate content had a little decrease, however, after topdressing nitrogen in crop growthperiod, the nitrate content would be temporary increasing,and then began to decrease. DCDcould reduce the N residue in the soil.3.To show DCD could reduce N loss as N₂O emission flux in the wheat-maizerotation system. In the level conditions of high, mid and low nitrogen, the emission flux ofN₂O from three treatments of DCD were all less than LN, MN and HN treatments,decreased by1.66%,7.40%and5.66%in the first season. The emission flux of N₂O fromthree treatments of DCD were all less than LN, MN and HN treatments, decreased by23.84%,26.06%and36.05%in the secend season. The emission flux of N₂O from threetreatments of DCD were all less than LN, MN and HN treatments, decreased by38.22%,33.52%and22.85%in the third season.