Fertilizer Nitrogen Loss Via N₂ Emission From Black Soil In Maize Field Of Northeast China

Nitrogen?N₂?emission from denitrification is an important aspect for the closed cycle of the global nitrogen and an approach to lose fertilizer nitrogen via N₂ emission.The black soil region of northeast China makes great contribution to producing cereals in China.Due to the limitation of denitrification measurement methods,the quantitative/estimation of fertilizer nitrogen loss via N₂emission is very inadequate in this area.In this research,we took the widely black soil in the Songjiang Plain as research object,and we divided it into three groups by using three different fertilization treatments,named straw+traditional fertilizer treatment group?S+Ncon?,straw+80%nitrogen fertilizer treatment group?S+Nopt?,no-straw+no-fertilizer-nitrogen treatment group(N₀).We determined N₂ and N₂O emission rates of the soil of different treatments in the maize season by using the helium-based gas-flow-soil-core technique.Here is the results.?1?Fertilization and rain would significantly enhance N₂ and N₂O emissions of farmland soils.S+Ncon group showed the highest N₂ emission on the 11th day after fertilization,which amounted to 9.9±2.3?g N kg^-1 h^-11 approximately 2970±690?g N m^-2 h^-1.the peak of N₂O emission appeared on the 18th day after fertilization,which was 2.1±2.1?g N kg^-1 h^-1approximately 630±630?g N m^-2 h^-1.The emissions of the N₂ and N₂O after fertilization and the N₂O/?N₂+N₂O?molar ratio are mainly affected by soil moisture;?2?The cumulative emissions of N₂ and N₂+N₂O of S+Ncon group in a month after nitrogen fertilizer application were 9.4±0.9 and 11.7±1.5 kg N ha^-1,respectively accounting for3.9±0.4%and 4.9±0.6%of nitrogen fertilizer input(240 kg N ha^-1).;?3?The effect of nitrogen fertilizer reduction treatment?S+Nopt?on N₂ and N₂O emission and N₂O/?N₂+N₂O?ratio is unclearer than traditional fertilization treatment?S+Ncon?.Besides the sampling measurements in mid-June,the nitrogen fertilizer reduction treatment has a tendency to reduce N₂O emissions and increase N₂ emissions,resulting in the decrease of the N₂O/?N₂+N₂O?ratio.However,the mid-June sampling observed higher N₂ and N₂O emissions and N₂O/?N₂+N₂O?ratios than traditional fertilization treatments group,mainly due to the high of inorganic nitrogen?NO₃^-and NH₄⁺?in the soil.The results above provide data support for fertilizer nitrogen loss via N₂ emission in black soil region of northeast China on maize season.Because of the large spatial heterogeneity in fertilizing farmland,the optimal measures of field management and nitrogen fertilizer application rates still needed to be further confirmed.