The Research About The Relationship Between Uncovering Plastic Film Period And Water Fertilizer Coupling Of Film Mulch Maize In Western Guanzhong Region

In recent years, film mulching techniques of maize had became a major cultivationpattern in the northwest semiarid region especially the western guanzhong region. But filmmulching for a long time could destroy soil structure, affected the quality of cultivated landand soil permeability, suppressed the absorption of moisture, nutrients and crop growth, andcaused production reduction, it also left a lot of plastic film residues, which made the “plasticpollution” to agroecological environment. As a result, there presented low efficiency of waterand fertilizer, and large gaps between attainable yield of maize grown with recommendedpractices and potential productivity in this region. In order to solve the problems, the effectsof uncovering plastic film periods under different water and nitrogen conditions on rootgrowth, physiology, growth, yield, utilization of water and nitrogen and comprehensivebenefits of film mulching maize in western guanzhong region were studied and systematicanalyzed by pot and field experiments. After studying I have preliminarily obtained somemajor research results as follows:（1）The evaluation of root-inducing effect of summer maize under different water levelsand uncovering plastic film periods was studied. By using the principle component analysismethod to evaluate root length, root surface area, root average diameter, root volume and rootdry mass, the results showed that principle component could represent92.09%primordial rootinformation with better representation and objectivity, and thus could be used as the maizeroot system evaluation. When uncovering plastic film at tasseling stage in the higher waterlevel (65%θF～80%θF), the highest comprehensive root index, dry matter accumulation,yield and water use efficiency were achieved.（2）The effects of water levels and uncovering plastic film periods on physiology,growth, yield and water use efficiency of spring maize were studied.The results showed that,during middle and late growth stage, the treatment of uncovering plastic film at tasselingstage under middle water level had the best stem diameter, underground biomass, root shootratio, root activity, leaf chlorophyll content and leaf MDA content, and better plant height,leaf area, total biomass, aboveground biomass and leaf Pro content, which had little difference between these values and the maximum (minimum). Moreover, compared with the max yield(the treatment of uncovering plastic film at tasseling stage under high water level:111.2g plant-1), the yield of uncovering plastic film at tasseling stage under middle water level(108.3g plant-1), had little difference, reduced by2.7%. The water consumption ofuncovering plastic film at tasseling stage under middle water level was significantly lowerthan all high water treatments, and its WUE (8.31g kg-1)) was significantly greater than othertreatments.（3）The effects of nitrogen rates and uncovering plastic film periods on physiology,growth, yield, WUE and NUE of summer maize were studied.The results showed that, duringmiddle and late growth stage, through increasing the root activity, uncovering plastic film attasselling stage increased the plant height, leaf area, and dry mass accumulation, improvedleaf photosynthetic rate, decreased leaf MDA content, and got better ear characters, yield,WUE, NAE and NPFP in comparison with mulching plastic film treatment under threenitrogen rates. However, there were no significant differences between uncovering plastic filmat jointing-tasselling stage and mulching plastic film treatments. With the same uncoveringplastic film period, applying nitrogen fertilizer was better than without nitrogen application inthe physiology, growth, yield, WUE and NUE of summer maize. however, there were nosignificant differences between high nitrogen and low nitrogen treatments. As the increasingof nitrogen rates, leaf photosynthetic, yield and water use efficiency decreased, and leaf MDAcontent increased. In this study, taking yield, water and nitrogen use efficiency andenvironment effect into consideration, the appropriate uncovering plastic film period andnitrogen rate of summer maize in mulched field in the Guanzhong Region were uncoveringplastic film at tasselling stage under N120kg hm-2.（4）The effects of uncovering plastic film periods on soil temperature in maize rootzonewere studied.The results showed that, uncovering plastic film at tasselling stage loweredtemperature, relieved the adverse effect of high temperature during the later growing season,ensuring a favourable environment of moisture, fertilizer, gas and temperature and to improveWUE, NUE and yield, thereby improved economic benefits. Removing the film early can alsodecrease environmental pollution and reduce recovery or reprocessing costs, a distinct butsmall advantage.（5）The multi-hierarchy and multi-objective fuzzy theory was applied to establish amulti-hierarchy and multi-objective fuzzy evaluation model of comprehensive benefits touncovering film maize. The results showed that, uncovering plastic film at tasseling stageunder middle water level got the optimal comprehensive benefits in the treatments of coupling of water and uncovering plastic film period, and uncovering plastic film at tasseling stageunder low nitrogen got the optimal comprehensive benefits in the treatments of coupling ofnitrogen and uncovering plastic film period. The results can be popularized in productionpractice. Therefore, the evaluation model of comprehensive benefits to uncovering film maizebased on information entropy theory can provide the reliable technical guidance for theoptimal uncovering film scheme of film mulching maize.