The Investigation Of Soil Carbon Dioxide Emissions Of The Summer Maize Farmland

This paper discussed the summer maize field ecosystems by using the staticchamber sampling on different soil moisture and different fertilization. Within2consecutive years of observation and research on the gas emissions in differentgrowth stages, using gas chromatography for sample analysis, we obtained the gasemissions rules of corn field greenhouse. The results are as follows:（1） Seasonal change of the summer maize soil CO₂emission increases and goesto the maximum within about sixty days. Then it drops. Low nitrogen concentration(N150mg·kg^-1) deal with summer corn soil CO₂emissions by a maximum of513.7mg/m²·h; high nitrogen concentration (N300mg·kg^-1) deal with summer corn in soilCO₂emission maximum is589.7mg/m²·h. The change is consistent with the summermaize growth cycle, in which the summer maize is usually at the most exuberant stageafter growth of sixty days. The temperature of5cm soil,10cm soil and20cm soil ofsummer maize significantly correlates with seasonal changes of its CO₂emission rule.（2） In different growth stage of summer maize, the intraday change of CO₂emission shows the same. It increases from night, and goes to the maximum at14:00.Then it falls. After applying three concentrations of nitrogenous fertilizer within allthe growth stages, the intraday change of CO₂emission shows great different. Theresult is that nitrogenous fertilizer increases the CO₂emission and that the amount ofCO₂emission is positively proportional to the concentration of nitrogenous fertilizer.In the same nitrogen concentration, the amount of CO₂emission at heading stage ismore than that of jointing stage and the amount at jointing stage is more than that ofmature period. For example: under nitrogen, the jointing stage of summer maize soilCO₂emission volume value of315.2mg/m²·h, the heading stage, soil CO₂emissionvolume value of454.2mg/m²·h, mature soil CO₂emission volume value of282.1mg/m²·h. The amount of CO₂release peaks at the heading stage.（3） The intraday change of CO₂emissions in different weather conditions showssimilar with （2）. All growth stages in the sunny days when the soil CO₂emissionsmean respectively: seedling160.6mg/m²·h, jointing337.0mg/m²·h, heading409.4mg/m²·h. The mean of CO₂emission in sunny days、cloudy days and rainy daysshows great difference. It can be when the weather is fine, summer maize soil CO₂emissions will increase somewhat. In the same weather conditions, the sort of CO₂emission in different growth periods is heading stage> jointing stage>seedling stage. Meantime, CO₂release peaks at the heading stage.（4） With three different soil moisture treatments, the soil CO₂emissions inseedling and jointing stages have changed obviously, which is increased in themorning and then decreased. With the condition of different soil moisture, the mean ofdifferent growth stage varies significantly. We can conclude that at the conditionwhich is soil water content accounts for70%of the field water holding capacity,summer maize soil CO₂emissions have increased significantly. Seedling stage whenthe value of237.3mg/m²·h, the jointing stage is351.9mg/m²·h.（5） Soil CO₂release in Jointing Stage and temperature of10cm soil aresignificantly related. The linear regression equation is y=9.8567x+21.82, of whichR²is0.8786（P<0.01）. Summer Maize heading Stage soil CO₂release and10cm soiltemperature was significant correlation, the linear correlation equation wasy=15.56x-49.112, R²was0.8358（P<0.01）. We can draw that the soil temperature andsummer maize soil CO₂emission are significantly correlated. The temperature is akey limiting factor.