Effects Of Mulching Culture On Soil Thermal-moisture Status, Yield And Water Use Efficiency Of Corn In Semi-arid Area

Corn (Zea mays L.) is the third mainly crop (inferior to wheat and rice) in China. its plantingarea is increasing yearly from1949to nowadays. However, the cropland area is decreasing withthe development of economy and town expanding, resulted in the restricted area of corn, and theproductivity of corn is determined by unit yield solely. Recently, whole field surface plasticmulching and double ridge-furrow planting (PMF), a new technology increased corn yieldsignificantly, is applied widely in arid and semi-arid northwestern China. However, there has nosystemic research on the mechanism of improvement of PMF. To explore these, field experimentwere conducted in dingxi county of Gansu province during2009-2010, where locates at hilly andsemiarid northwest Loess plateau. Three treatments involved in the field experiment,1) wholefield surface plastic mulching and double ridge-furrow planting (PMF),2) whole field surfacesand mulching and flat planting (SM), and3) flat planting without mulching (CK), designedrandomly and replicated three times. Soil temperature, soil water storage, crop growth index, drymass, water consumption in different growth stages, water use efficiency, yield and yieldcomponent of corn were determined and analyzed. The main results are as follows:1. PMF increased soil average temperature about3℃in0-25cm soil profile duringSeeding-Heading stage of corn, as compare with CK, improved corn development in early growthperiod. Soil temperature of PMF was linear correlation with air temperature, but responsiblesensitivity was lower than SM and CK, especially in10-25cm soil profile. Therefore, PMF couldsustain relative stable soil temperature, benefit to corn development. SM also could improve andsustain relative stable soil temperature, but the impact was not significant as PMF.2. At the minimum soil temperature point, soil temperature gradient (Gra) of three treatmentswas positive, the deeper soil heat transported to surface. However, the Gra was opposed at themaximum soil temperature point. Before corn jointing, whether at the minimum or maximum soiltemperature point, Gra followed the sequence as PMF﹥SM﹥CK, soil thermal conductivity ofPMF was stronger than SM and CK. From corn jointing to harvest, Gra followed the sequence asPMF﹥SM﹥CK at the minimum soil temperature point, and followed the sequence as PMF＜SM＜CK at the maximum soil temperature point, then, it suggested that soil thermal conductivity of PMF was stronger at lower soil temperature condition, weaker at higher soil temperature stage,plastic mulching adjust the characteristics of soil thermal conductivity, keep the relative stable soiltemperature, therefore, PMF improve corn growth, advance corn growth stage, shorten the wholegrowing stage, especially, extend the reproductive growth period, its benefit to corn filling.3. PMF could improve soil water storage in0-200cm profile and reduce evaporationsignificantly before corn jointing, enhance the soil water capacity, the more soil water sustainedfor later corn development. As compared with SM and CK, before corn jointing, PMF increasedsoil water storage by9.5mm and18.2mm in0-60cm soil profile, by13.7mm and9.6mm in60-120cm soil layer in2009, and by24.7mm and6.9mm in0-60cm soil layer, by8.6mm and14.2mm in60-120cm soil layer in2010, respectively. With the corn growth, there was a significant differencein water consumption between three treatments, which followed the sequence as PMF>SM>CK.Conversely, the change of soil water storage followed as CK>SM> PMF.After corn jointing, cornwater consumption accelerated, the most significantly stage was filling, then was the stage fromjointing to heading. During corn filling stage, as compared with SM and CK, water consumptionof PMF increased by72.0%and190.8%in2009, by84.5%and237.7%respectively in2010,during corn jointing-heading stage, water consumption of PMF increased by8.2%and23.9%in2009, by8.2%and37.8%respectively in2010. Thus, PMF could sustain a relatively better watercondition for corn reproductive growth. The water consumption peak was adaptive to thedynamics of precipitation. SM also could reduce evaporation and promote water use inreproductive growth period, but the effect was not significant as PMF.4. PMF increased soil temperature, soil water storage during corn growth early stage,increasd corn water consumption, therefore, improved leaf growth and biomass accumulation ofcorn. Leaf area index (LAI) of PMF was higher than SM and CK through whole corn growingstage and keep higher LAI in whole reproductive growth period, therefore, dry matteraccumulation of PMF was highest among three treatments, better vegetative growth supportreproductive growth and yielding. PMF and SM elongated reproductive growth period andaccelerate water consumption during corn reproductive stage, keep higher water use efficiencybiomass(WUEb) in whole reproductive growth period, benefit to the using of light, heat and water.Therefore, spike length, grain number per spike, grain weight per spike,100-grain weigh of cornwere increased significantly. For example, corn yield, harvest index (HI) of PMF increased by310.0%-356.2%and95.3%-169.6%respectively, as compared with CK. Likely, SM also increased corn yield and HI by224.3%-256.1%and76.1%-156.0%, respectively.5. WUEband WUEgof PMF were higher than CK significant, as well as SM treatment. AsCompared with CK, PMF and SM not only improved WUEb, but also kept higher WUEbthroughcorn reproductive growth period. After corn heading, WUEbof PMF decreased by4.8-6.1%,WUEbof SM decreased by5.8-7.9%, and WUEbof CK decreased by9.0-25.6%, resulted in theincrement of WUEgby265.6%-315.5%in PMF treatment, by204.9%-249.3%in SM treatment,respectively, as compared with CK.6. PMF increased corn yield continuously, but speeding up the soil water cycle andconsumption, as well as increased the water loss in deeper soil profile. Thus, the restored depth ofsoil water in0-200cm soil profile was deepest in PMF treatment under the same annualprecipitation, and then was SM, CK was shallowest. Under PMF treatment, the quicker soil waterloss promoted the speed of soil water restoration, further, the quicker soil water restoration drovethe crop water consumption, so the quantity and depth of soil water consumption in PMFtreatment increased with the increases of corn planting years. For example, from2009to2010, thedepth of soil water loss increased from20-120cm profile to120-200cm profile. After2years corncontinuous cropping, soil water content in40-120cm profile was less than9%in all threetreatments, especially, the soil water content of PMF treatment was7.9%, closed to the wiltingcoefficient (7.2%), corn development only depending on rainfall in growth season. The dynamicof precipitation was not coincide with corn water need in the experimental area, the continuouscorn cropping with PMF probably caused soil dry layer in semiarid area. Therefore, PMF couldimprove corn yield significantly, but continuous cropping may result in the significant reductionof soil water storage, and was disadvantage to the sustainable the balance of soil water storage.We can conclud that PMF firstly increased soil average temperature in0-25cm soil profileduring Seeding-Heading stage, increased Gra and0-200cm soil water storage before jointing stageof corn, improve corn development in early growth period. Secondly, PMF increased waterconsumption during corn reproductive growth stage, especially filling stage, promoted thetransferring of energy to grain, improved filling, benefit to the using of light, heat and water, thus,spike properties of corn improved significantly, spike length, grain number per spike, grain weightper spike and then yield, WUE(WUEband WUEg) of corn increased significantly. But, the costwas the huge consumption of soil water. For example, from2009to2010, the depth of soil waterloss increased from20-120cm profile to120-200cm profile. After2years corn continuous cropping, soil water consumption in0-200cm was up to163.6mm, soil water content in40-120cmprofile was7.9%, closed to the wilting coefficient (7.2%), corn development only depending onrainfall in growth season, the potential risk increased that soil water balance was broken and soilwater ecosystem was deteriorated. Therefore, effect of PMF on crop and soil was drove by Gra,taken by transferring of soil heat and water, was advantage to corn but disadvantage to soil waterecosystem.