CO₂&NH₃Emission In Winter Wheat Field With A Plastic Mulched-ridges And Unmulched Furrows

To study the effects of plastic mulched-ridges and unmulched furrows （PMRF） onammonia volatilization and soil respiration in winter wheat field. We used the enclosurechamber method to quantitatively determine the ammonia volatilization and an SR1LPchamber for soil CO₂emission. The dynamics of the soil ammonia volatilization and soilrespiration with the soil property were investigated in the different cultivation patterns. Thetested cultivar is Xiaoyan22. The field trials were conducted from Oct.2009to Jun.2011atYangling, Shaanxi province.1. In the growth season of winter wheat, the accumulation loss of volatilized NH₃wasmost intense during the first2weeks after sowing. The soil ammonia volatilization beforewinter accounted for more than82%-95%of total NH₃emission in conventional flat practice,and only49%-86%in PMRF. It was implied that soil ammonia volatilization mainly occur inthe first month after seeding, and had a great drop after turning green stage. The simulationresults indicated that ammonia accumulation loss complied with Elovich dynamic equationbefore the winter, and linear equation after turning green stage.2. The PMRF could significently reduce the ammonia volatilization by changing themechanism. In2009-2010, the volatilization amount in the plots with PMRF under the Napplication rate180kg·ha^-1（RM180） and240kg·ha^-1（RM240） were1.9±0.2kg N·ha^-1and2.4±0.7kg N·ha^-1separately, and the amount of conventional practice with nitrogenapplication rate180kg·hm^-2（TF180） was4.3±0.8kg N·ha^-1. Compared to the conventionalflat planting system, the PMRF could reduce volatilization amount by56.3%and43%, and Nloss rate dropped from1.6%of conventional practice to0.2%-0.4%of PMRF. The results ofthe trial during2010-2011indicated thatNH3emission rate in the PMRF practice were1.66±0.3kg N·ha^-1-3.28±0.51kg N·ha^-1, and4.68±0.35kg N·ha^-1of the conventional flatpractice. Compared to the conventional flat practice, the PMRF couldreduceNH3volatilization by29.8%-63.8%. The NH₃emission loss was1.9%of the applied Nin conventional practice, but the loss was only0.3%-0.8%of the applied N in FRFM practice.3. Laboratory simulation experiment show the deep application of N fertilizer had moreeffects than plastic film mulch on limiting ammonia volatilization. The ammonia volatilization of conventional practice before winter was affected by the soil NH₄⁺-N contentand soil moisture, but it was affected by the NH₄⁺-N content and indirect effected by the soilsurface temperature and soil moisture of PMRF. The ammonia volatilization of traditionalpractice and PMRF was mainly influenced by the concentration of soil NH₄⁺-N content afterturning green stage. The PMRF could significantly reduce the ammonia emission loss owingto change the dynamics and mechanism of the soil ammonia volatilization temporally andspatially.4. There were significant seasonal variations in soil respiration. Soil respiration waslowest during the winter when the wheat was in the seedling stage and highest during thesummer when the wheat was mature. The data suggested that soil CO₂emission in theplastic film mulched-ridge （RM） was greater than that in an unmulched, smooth field （TF）.Furthermore, CO₂emission rates from the plastic film-mulched ridges were greater than thosefrom the unmulched furrows （FU）. The mean soil CO₂fluxes were1.14±0.20μmolCO₂·m^-2·s^-1from the unmulched, smooth field,2.06±0.44μmol CO₂·m^-2·s^-1from the plasticfilm-mulched ridge, and0.75±0.11μmol CO₂·m^-2·s^-1from the unmulched furrow. DiurnalCO₂emissions from plastic film-mulched ridges, unmulched furrows, and unmulched,smooth fields followed similar patterns during the winter and early spring. Specifically, CO₂emissions increased during the morning, reached a peak around noon, and then decreased inthe afternoon. In contrast, there were differences in diurnal CO₂emissions among thetreatments after jointing stage. There was a double peak in soil CO₂emission from plasticfilm-mulched ridges. However, CO₂emissions from unmulched furrows and unmulched,smooth fields remained steady throughout the day.5. Soil respiration was significantly correlated with soil temperature at the5cm depth.Soil respiration increased as the soil temperature increased from10to24-31°C. Soilrespiration decreased at soil temperatures>31°C. The effect of soil temperature on soil CO₂emission was best described by a quadratic function, whereas the interactive effects of soiltemperature （T） and soil moisture （W） on soil CO₂emission were best described by thefollowing equation: f（R）=a（bT2+cT）（1+dln（2W）/T）+e.