Influence Of Cover And Straw-returning Approaches On Soil Temperature Of Wheat In Dryland Area

The experiment was conducted to study effects of different mulching and strawreturning models on soil temperature in0~25cm soil depth， yield and yieldcomponents of winter wheat in a Semi–arid Loess Plateau of Northwestern Chinafrom2011to2013. The experiments comprised of two parts, one is about mulchingmodels, ie, the whole maize straw zonal mulching（T1）, wheat straw choppingmulching（T2）,plastic film mulching added1cm soil depth above（T3）and mulchingplastic film in double furrow（T4）. The other is about straw returning models, ie,maize straw returning+mulching plastic film and adding1cm depth soil above plasticfilm+rolling at pre-sowing (A1), maize straw returning+rolling at pre-sowing (B1),maize straw returning (C1), wheat straw returning+mulching plastic film and adding1cm depth soil above plastic film+rolling at pre-sowing (A2), wheat straw returning+rolling at pre-sowing (B2), wheat straw returning (C2). The mainly results were asfollows:1. There were same changing trends between soil and air temperatures under theconditions of different mulching and straw returning models. Soil temperature fellfrom seedling to the over-wintering stage, and rise after over-wintering stage. The soiltemperature of the upper depth was higher than that of the lower when air temperatureis lower, but the phenomena was opposite at high air temperature.2. Effects of mulching models on soil temperature were significant, T4had thehighest soil temperature and T1was minimum. However, there was different warmingor cooling effect during the whole growth stage. T4showed warming temperatureeffects during the whole stages;T3showed warming effect only before the jointingstage；T1and T2increased soil temperature when they were at over-wintering stage.3.Effects of mulching models on daily variation of soil temperature showed：Straw mulching decreased soil temperature while mulching plastic film increased soiltemperature in a whole day. Mulching could slow the fluctuation of soil temperatureamong different seasons.4. There were different effects about the materials and years of mulching and farming models. In the materials of straw returning, warming effect of wheat strawreturning was higher than that of maize, and cooling effect was on the contrary by twocontinuous field experiments.The influence of straw returning on soil temperature was different in differentyears. The result showed there was warming effects during the growth stage of winterwheat under the condition of one year straw returning field, C2had the highest soiltemperature and CK was minimum. However, the effects of two years straw returningon the soil temperature had dual function. Warming effect was from seedling stage toelongation stage while cooling effect was from booting stage to ripening stage, andthe effect cooling effect is greater than that of warming. All of treatments showedcooling effect except A1, whats more C1had the largest cooling effect and C2wasminimum.The effects of straw returning on soil temperature were different in a day.Generally, there was warming effect in the morning and cooling effect after12:00h.The daily amplitude variations of soil temperature of unrolling were greaterthan that of rolling.The adjustment effects of soil temperature of mulching and farming models werenot the same in different years, so did straw returning. For example, soil temperatureof no rolling was greater than that of rolling in the first year of straw returning, and itwas opposite in two years.5. Yield was increased by mulching and straw returning. In all treatments ofmulching, The rate of increasing yield was, in order, T3（60.5%）＞T1（51.8%）＞T（433.5%）＞T（230.2%）. Both spikes number per area and grain number of mulchingwere higher than those of CK, but1000-grain weight of each treatment decreasedexcept T4, and higher by1.6g than that of CK. In a word, T4had the highest of yieldand yield components.In the treatments of straw returning, A1had the highest yieldand greater by110.81%than that of CK. What is more, the rate of increasing yield bytwo years straw returning was greater than that of only one year. The yield of alltreatments showed: maize straw＞the wheat straw，mulching plastic film＞CK， rolling＞no rolling. Further analysis found that the cause of increasing yield was grainnumber improved.In this study, in order to solve pollution and improve yield, T1, T3and A1could bechosen to meet sustainable development of dryland agriculture, and suitable forrainfed agricultural area in the northwest loess plateau region for its high-efficient,high-yield and health.