Study On The Characteristics Of Greenhouse Gases Flux And Its Simulation In Maize Field Under Different Fertilization Management

This field experiments were located in Yuci county, Jinzhong area, Shanxi Province. Two fertilization management practices were selected. They are: (1) traditional fertilization as (Trad); (2) optimized fertilization as(Opt). Emission fluxes of N₂O, CO2 and CH₄ for spring-maize field was continuously measured by automatic chambers, studied on the influence of fertilization management practices on greenhouse gases(GHG) emission. The objective was to find a management which can reduce GHG emission and studied the contribution of maize to N₂O emission. Integrated evaluation of these treatments was provided by taking grain yield and N₂O emissions into consideration; Use the field observation data to calibration and validation the Water and Nitrogen Management model (WNMM). The calibrated and validated WNMM was then used to simulate N₂O emissions from this soil to find significantly correlated factors to N₂O emission from spring-maize field. This research is important to evaluate GHG emission from agriculture and explore the methods to abate GHG emission. The main results are as follows:1. Measurement resultsThe typical diurnal variation of CO2 flux showed a concave shape in 2006 and a double peak shape in 2007. The CO2 flux has a significant correlation with air temperature in 2006 and has a significant correlationship with soil temperature at 5cm depth and 10cm depth. In general, the CO2 and the CO2 flux from optimized fertilization maize field didn't show any significant different compared with which from traditional fertilizated maize field.The typical diurnal variation of CH₄ flux didn't showed any regularity, we can found that the maize field could absorb some CH₄ from the air. The CH₄ absorbability from Opt is larger than Trad, which indicated that the N fertilizer can inhibiton the CH₄ absorbability of the maize field. In general, emission CH₄ and the CH₄ flux from optimized fertilization maize field didn't have any significant different with which from traditional fertilizated maize field.The typical diurnal variation of N₂O flux showed single peak shape , double peak shape and"N"shape, so the maize field manifested as N₂O emission source. The N₂O emission was mainly influenced by the tillage, top dressing, irrigation and precipitation. The influences of tillage, top dressing and irrigation on N₂O emission is account about 80%. N₂O flux from maize field with optimized fertilization was very significant lower than that with traditional fertilization (p<0.01). Maize do emit N₂O, but the regularity and mechanism of the crop emission isn't clear, so it need further study.2. WNMM simulationThe Water and Nitrogen Management model (WNMM) was calibrated and validated to simulate N₂O emissions from semiarid and maize-cropped soil system on a loam soil at yuci, North Plain of China(NPC)from May 2007 to september 2007. The calibrated and validated WNMM was then deployed to simulate N₂O emissions from this soil from 1951 to 2007 for nine scenarios of N fertiliser application and nine water management respectively at yuci. This sensitivity test found that the annual N₂O emissions for this semi-arid and intensively cultivated maize-cropped system were significantly correlated to annual N fertiliser application rate (r=0.99) and maize yield (r=0.43). Based on this 57-year simulation, multivariate regression models for estimating annual N₂O emissions were developed (by the fertilization, crop yield, temperature difference, annual average daily radiation and precipitation) for this semi-arid and intensively cultivated maize-cropped system in NPC, which explained over 97% of yearly variations of annual N₂O emissions predicted by WNMM.3. The integrated evaluation of agricultural management practicesThe results of this research showed that the N₂O flux from maze field with optimized fertilization was very significantly lower than that with traditional fertilization and the CH₄ absorbability from Opt is stronger than Trad,meanwhile the crop yield from Opt is not lower than Trad, so evaluation based on crop yield and GHG emissions showed that the Opt is a better management practice for it not only could reduction N₂O emission but also it could reduction farmer's input on fertilization, and it didn't at the cost of crop yield.