Effect Of Nitrogen Application Methods On N₂O,CO₂Emissions And Nitrogen Balance In Typical Black Soil Farmland

In order to understand the effects of N fertilization application methods on the CO2and N2O emission flux and nitrogen balance in a maize field of cold blackland, this field experiments were observed continuously the CO2and N2O emission flux in maize were by using closed static chamber-GC/MS technique from Seedling to Harvest stage. The connection between soil water content, soil temperature and the emission flux of CO2and N2O was discussed, and the effects of different N fertilization application ways on dynamic altering of inorganic nitrogen and nitrogen balance were also explored. The conclusions of this research are as follows:1. Maize field N2O emission under different treatments showed similar variation trend with single maxima from maize Seedling to Maturity stage. For whole period, N2O emissions average fluxes under the different nitrogen level was different following the sequences:N240>N180>NO. Meanwhile, nitrogen application methods had different effects on N2O emissions showed BU(40%B+60%T)>BU100%B>40%BU+60%CRU(B)> CRU100%(B),which was increased as the soil temperature and rainfall on trends. Seasonal changes of N2O emission flux in maize field shown in sequence:Tasseling-booting stage>Jointing stage>Filling stage≈Seedling stag>Maturity stage. The seasonal changes of N2O emission flux in Tasseling-booting and Jointing stage showed more significantly than in others stage, which explained that the effects N fertilizer on N2O emission flux was more significantly at prophase and metaphase of maize growth.2. Consistent with the N2O, CO2emission of treatments showed similar variation with single maxima throughout the reproductive age, those ranged from327.60to1787.68mgC·m-2·h-1. Variation of annual CO2emission flux at different N levels showed N240N180> NO.Meanwhile, nitrogen application methods had different effects on CO2emissions showed BU100%B> BU(40%B+60%T)>40%BU+60%CRU(B)>CRU100%(B), the changes were increased as N levels and common urea ratio. Seasonal change of CO2emission the growth period of maize followed as:Tasseling-booting stage>Jointing stage>Filling stage>Seedling stag>Maturity stage. The changes was significant in each growth stage except in Mature stage.3. The soil water content has complex effects on CO2and N2O emission flux of maize field during the whole maize growth period. For specific performance, CO2and N2O emission flux were increased with soil water content under condition of suitable moisture, but reduced with the increasing soil water content when the soil water within a limited range. There was significant positive correlation between nutrient release of the CRU and soil temperature in correlation analysis, thus correlation analysis showed that correlation between soil temperature and CO2and N2O emission flux of40%BU+60%CRU(B) and CRU10O%(B) treatments was also significant. CO2emission flux, soil moisture content and soil temperature were positive correlation of all treatments, particularly was high between soil moisture content. It was manifested as higher soil temperature and relatively low soil moisture favor CO2emission.4. The controlled-release urea could keep the content of NH4+-N, NO3--N in each layer soil at certain level and further made soil maintain higher N-supply level. Under the same nitrogen application regimes, apparent nitrogen loss of treatment6[N240BU(40%B+60%T)] increased32.1kg·hm-2compared with treatment2[N180BU(40%B+60%T)],and that illustrated losses of nitrogen increasingly with nitrogen rate. Compared with treatment4(BU100%B), apparent nitrogen loss of treatment5(CRU100%B) reduced12.1kg-hm’2, suggesting that control release urea could effectively mitigate fertilizer N residue in soil under the same N level.5. According to the calculations of nitrogen balance in soil-plant system under different N application methods, the use of controlled-release urea could significantly improve nitrogen use efficiency and reduce the content of residual inorganic nitrogen after harvesting, so that the loss of nitrogen reduced. Especially treatment40%BU+60%CRU(B),which the controlled release urea and urea mixed fertilizer, had the highest nitrogen utilization efficiency, agronomic efficiency, physiological efficiency and partial factor productivity of applied, were42.6%>19.6kg/kg、46.0%and63.7kg/kg respectively.6. In a certain range, maize yields were increased with the increase of nitrogen. But the effect was not significant when superfluous nitrogenous fertilizer application. The best maize output of biological and economic under different processing conditions was N18040%BU+60%CRU(B) treatment, treatment N180BU(40%B+60%T) followed by and N240treatment the third. Among them, treatment of40%BU+60%CRU(B) was the most optimal type of N-fertilizer application in black soil corn agroecosystem, which significantly improved nitrogen use efficiency and economic benefit while significantly reduced the N2O and CO2emissions and N2O emission factor, lowered risk of inorganic nitrogen loss leaching to the deeper soil layer by kept steady content of nitrate-nitrogen in soil.