Waterandheat Transport And Evapotranspiration Process Under Sand-gravel Mulch In Summer Maize Field

Gravel mulch is a kind of comprehensive efficiency of dry cover technology.It has obvious improvement and adjustment effect of farm environment,gravel mulch can play the effect of temperature, water storage, soil moisture. In recent years, sand-gravel mulching has been widely used in agricultural production.The experiment was conducted at the Northwest Agriculture and Forestry University Chinese Institute of water saving agriculture in arid regions in June to October of 2015 and 2014.Tests were set up four levels of gravel cover thickness:1cm,2cm,3cm,4cm,and two irrigation levels 0,50 mm, which resulted in five no-irrigation-mulching treatments(SDCK,SD1,SD2,SD3,SD4) and five irrigation-mulching treatments(ISDCK,ISD1,ISD2,ISD3,ISD4).The study compared and analyzed the changes of evapotranspiration and soil evaporation under different mulching conditions,and the variation of soil temperature and heat flux. Some main conclusions have been drawn as follow:(1)The surface 5cm of soil temperature changes much, the ground temperature at 10 cm, 15 cm, 20 cm, 25 cm fluctuations are decreased, 25 cm at ground temperature changed slowly. Sand and gravel cover had a significant effect on the temperature of the surface soil, and the soil temperature increased with the increase of the cover thickness. In a day, the soil temperature in the 8:00~14:00 moment is in a warming up stage, and the soil temperature in the 14:00- 18:00 moment is in the cooling stage,showing the trend of increasing first and then decreasing.Among them, the 8:00 time temperature can be represented within a day of the lowest temperature, 14:00 can represent the highest temperature within a day.In addition, the relationship between the temperature and the temperature can be fitted by a power function.(2)During the whole growing period, the soil heat flux is positive, and the soil absorbs heat. And the heat flux in soil conditions under the gravel covered more than bare ground control.The trend of change trend of heat flux and average temperature are same, and the heat fluxreaches its maximum at the beginning of July,with decreasing temperature, soil heat flux also showed a decreasing trend.(3) Gravel mulchcan restrain soil surface water evaporation, achieve the effect ofsoil moisture conservation, thus contributing to the growth and development of plants.During the whole growth period,the soil evaporation of bare control was higher than that of gravel mulch, and with increasing thickness, soil evaporation decreases, namely SDCK> SD1> SD2> SD3> SD4.In summer corn growth period,the ratio of soil evaporation(Es) and evapotranspiration(ET) was different in different growth stages.The ratio of Es and ET was larger in the seedling stage, and the ratio of Es to ET decreased after entering the jointing stage, and the Es and ET value increased after the mature period.(4)During the whole growth period,the variation of evaporation and transpiration was increased from seedling stage to jointing stage, and decreased from jointing stage to booting stage, and heading to filling stage increased, and grain filling to maturity stage decreases. The evapotranspirationunder gravel cover conditions were less than bare ground control,and the thicker the gravel-covered, the less evapotranspiration, namely SDCK>SD1>SD2>SD3>SD4. The transpiration rate of five treatments of irrigation was higher than that of no irrigation treatment.The evapotranspiration in 2015 was higher than 2014,which was due to the small amount of maize leaf area index in 2014,and the amount of rainfall, which affected the transpiration of plants, and the evapotranspiration were small.