Effects Of Plastic Mulching And Irrigation On Soil Thermal Characteristics And WUE Of Corn

Recently, studies on water use efficiency based on grain yield have been widelyreported while it still lacks systematic theoretical basis for effective water-savingmethods in agronomy. It is seriously considered that studies on effects of plasticmulching on soil thermo-hydraulic characteristics on farmland scale were on theurgent agenda. Besides, phase water use efficiency at various growth stages of maizeis still lack of systematic evaluation. Field maize was taken as research object inShiyang River Basin, one of most water deficient regions in Hexi Corridor, Gansuprovince. A field experiment was carried out to investigate the effects of differentmulching and irrigation regimes on soil thermo-hydraulic characteristics, and therelationship between phase water use efficiency based on biomass accumulation（WUEET.B） and WUE based on grain yield （WUEET.Y）, as well as key factors impactingWUEET.Band WUEET.Y. Main results were concluded as follows:1. Grain yields under whole mulching with high irrigation level, whole mulchingwith moderate irrigation level, and half mulching with high irrigation level on aridland were achieved to13275.5,12880.5, and12409.9kg ha-1, respectively. This wasattributable to improved kernel number,100-kernel weight, and double cob rate underthose three treatments. Irrespective of mulching patterns, high irrigation levelincreased those three yield components compared to moderate and low irrigation level.Whole mulching with high irrigation level significant increased those three yieldcomponents, with their values averaging659kernels per cob、36.4g per100-kernel,and23.9%, respectively. Irrespective of irrigation regimes, whole mulching increasedthose three yield components and leaf areas per plant.2. Plastic mulching and irrigation regimes had significant effects on phase andtotal water consumption. Total water consumption increased as the irrigation quotaincreased, reached the maximum at high irrigation level followed by moderate levelwhile the minimum was taken from maize at low irrigation level. Effect of differentmulching on water consumption was insignificant （P <0.05） under the same irrigationlevels. Under whole mulching condition, high and moderate irrigation levels increasedwater consumption by25.3and13.5%as compared to low irrigation level whileunder half mulching the percentage increases in water consumption were25.2and 11.7%, and, under no mulching treatment, were28.4and14.3%. From seedling tojointing, phase water consumption was highest in no mulching followed by halfmulching and lowest in whole mulching. However, from jointing on, phase waterconsumption was increased as the irrigation quota increased.3. Deficit irrigation is an effective way to improve water use efficiency, as wellas the WUEET·B. Under the same irrigation quota, whole mulching obtained the highestWUEET·Yfollowed by half mulching and no mulching resulted in the lowest WUEET·Y.WUEET·Ywas highest in maize under whole mulching with low irrigation level,averaging at19.9kg ha-1mm^-1while was lowest under half mulching with highirrigation level, averaging at13.3kg ha-1mm^-1, a decline by33.2%compared to theformer treatment. There was a positive correlation between WUEET·Yand WUEET·Bduring bell mouthed to filling. In contrast, there existed significantly negativecorrelation between WUEET·Band corresponding ET, E, and E/ET during seedling tojointing, and bell mouthed to flowering, respectively. Similar treatment effect wasalso observed between WUEET·Yand corresponding ET, E, and E/ET.—4. Transpiration rate （Tr） is not susceptible to irrigation quota under the same—mulching treatment across the growing season while the response of Tr to mulchingpatterns was significant （P <0.05）, irrespective of irrigation levels. Under wholemulching condition, photosynthetic rate peaked at heading stage while the maximu—rate appeared at middle filling stage under half or with no mulching. An under wholemulching with moderate irrigation was highest across treatments during growing—season (averagely47.0mmol m^-2m^-1). Tr under whole mulching was significantlyhigher than that of half and no mulching during bell mouthed to filling. Under high—irrigation level, Tr under whole and half mulching was10.1and8.2mmol m^-2m^-1,respectively. Leaf photosynthesis and transpiration were the processes that showedsynergistic effect and closely coupling between them. Under whole mulchingcondition, WUElwas not susceptible to irrigation quota, whereas WUElwith nomulching was significantly higher than that of whole mulching under the same——irrigation level. There was a positive correlation between Tr and An whilecorrelation between WUEland WUEE.TB, and WUEland WUEET.Ywas not significanteven at P <0.05. 5. Mulching and irrigation significantly influenced soil water content in the0-30cm soil profile while the effects on soil water content in the30-110cm soil profilewas insignificant （P <0.05）. Soil temperature at0-30soil depth simultaneouslychanged with air temperature. Thus mulching treatment not only improve watercontent in top soil, but also increased soil temperature at0-30cm depth while itexhibited a negative correlation between soil water content and soil temperature at agiven depth. There were negative correlations among accumulated soil temperature at0-30cm layer and soil water content and WUEl.