Growth And Evapotranspiration Components Of Spring Maize Planted In Furrow With Plastic Mulched Ridge

Dynamics of soil moisture and evaporation, farmland evapotranspiration, and growth process ofrain-fed spring maize are monitored continuously for two years in plastic mulching and un-mulchingfields of dry-farming experimental zone in Shouyang County, Shanxi Province, and the changingregularities of field evapotranspiration components are also analyzed to explore crop water useefficiency in different stages of growth period and different levels, so this paper seeks to reveal themechanism of plastic mulching enhancing maize yield. The main conclusions are as follows:1. In comparison with un-mulching treatment, the temperature of soil surface layer inside andoutside the plastic mulching area increases by an average of0.8℃and0.2℃respectively, averagevolumetric moisture content relatively increases by3.12and3.68percentage points respectively. Airtemperature and leaf area index are important factors that affect the temperature of soil surface layer,what is more, soil initial moisture content in soil depth of20cm, rainfall, leaf area index are importantfactors that affect the volumetric moisture content of soil surface layer, overall determinationcoefficients (R Square) are more than0.75. In addition, compared with un-mulching treatment, thevolumetric moisture content of soil depth of10cm inside plastic mulching area dramatically increasesby7.6%, soil depth of20cm has a4.5%increase, soil depth of30cm has the lowest increase of0.4%.2. Spring maize variety is Jingdang-951in2011, plastic mulching treatment has seedling emergencerate of97.8%, which is significantly higher than83.4%of un-mulching treatment, in addition, with thehelp of plastic mulching, each growth stage of spring maize emerges an average of7days in advance,meanwhile, whole growth period shortens11days; Compared with2011, Spring maize variety isXianyu-335in2012, plastic mulching treatment has seedling emergence rate of95.3%, which is higherthan90.2%of un-mulching treatment, each growth stage of spring maize emerges an average of8daysin advance, and whole growth period shortens12days. Moreover, the leaf area index (LAI), plant height,aboveground and underground dry matter of plastic mulching treatment are significantly higher thanun-mulching treatment by110.2%,13.5%,42.9%and12.7%respectively in2011, by91.2%,25.4%,79.2%and71.1%respectively in2012. The biomass and seed yield per unit area in plastic mulchingarea increase by14.9%～21.9%and12.1%～14.3%respectively. At the same time, the plastic mulchingalso markedly improves grain water use efficiency by21.7%～30.3%to2.86～3.81mg/g.3. Before June of maize jointing stage and from August to mature stage in2011, average dailyevapotranspiration of plastic mulching treatment is lower than un-mulching treatment by6.8%and0.4%respectively, but between June and August, average daily evapotranspiration of plastic mulchingtreatment is higher than the latter by5.1%. Overall evapotranspiration of plastic mulching treatment inwhole growth period is376.2mm, lower than un-mulching treatment by6.0%, and soil evaporation islower by57.7%. Before June and from July of maize jointing to mature, average dailyevapotranspiration of plastic mulching treatment is lower than un-mulching treatment by19.4%and8.4%～11.5%respectively, but from June9to June28, leaf area index of spring maize in mulching area is significantly higher than un-mulching area by67.3%, it exists the biggest difference in these twotreatments at this period, and average daily evapotranspiration of plastic mulching treatment is higherthan the latter by22.5%. Overall evapotranspiration of plastic mulching treatment in whole growthperiod of2012is318.4mm, lower than un-mulching treatment by13.9%, and soil evaporation is lowerby51.4%. In addition, Dividing coefficient (η) is the share of the bare soil evaporation in fieldevapotranspiration, average daily dividing coefficient of mulching area in the whlole growth period is0.232, significantly lower than37.0%of un-mulching area, which average daily dividing coefficient is0.368. Dividing coefficient is highly index-correlated to leaf area index, determination coefficients (RSquare) of un-mulching and mulching treatments are0.980and0.876separately.4. Water ues efficiency rule in levels of dry matter accumulation of WUEdma_Tand WUEdma_ET,ecosystem of WUEecoperforms for the birth earlier period low, the intermediate stage is high, the laterperiod slightly low changes tendency, and the three levels of water use efficiency behave extremelysignificant linear relationship, determination coefficients (R Square) are more than0.65. AverageWUEdma_T, WUEdma_ETand WUEecoof whole growth period in mulching area are significantly higherthan un-mulching by60.0%,23.7%and37.2%respectively.It is thus clear that, plastic mulching technology retains soil water and heat to promote maizegermination, advances growth stages, increases dry matter accumulation rate by higher increments,significantly reduces soil evaporation and field evapotranspiration, and then saving water is used forcrop transpiration to increase the assimilation of biomass. Eventually, it can improve biomass andeconomic yield per unit area and crop water use efficiency significantly. In addition, compared withdifferent planting varieties in these two years, spring maize of Xianyu-335has stronger photosynthesis,faster dry matter accumulation, lower field evapotranspiration, higher yield of economic, biomass andwater use efficiency per unit area, so it is ideal for choosing Xianyu-335to plant in this region.