Simulated Study On Effects Of Soil Managements On Soil Water And Temperature For The Jujube-soil System

Land cover is an important method to solve the problems of drought and soil and waterloss. As the prevalence of clean cultivation in dryjujubes on the Chinese loess plateau area,different surface coverage measures were introduced to the jujubes. This paper systematicallyanalyzed the effects of different surface coverage measures on soil physical structure, soilwater holding capacity, soil hydrothermal regime, and the relationship between soilmoisture and soil temperature. Treatments in this simulated investigation included: strip whiteclover cover+jujube branch mulching (JBM+SWC), whole jujube branch mulching (WJBM),strip white clover cover (SWC) and clean cultivation (CC). We got the following conclusions:1. Vegetation cover and jujube branch mulching improved soil structure, increased soilpore, and reduced soil bulk density; the rank of soil water-holding capacity and specific watercapacity at different soil suction stages under different treatments were: JBM+SWC>WJBM> SWC>CC, and these differences was significantly obvious at high sanction stage;the saturation moisture content, field soil moisture content, and wilting point under vegetationcovering and jujube branch mulching treatments increased by9.11%,20.32%, and33.4%,comparing with CC, in particular under JBM+SWC.2. During Jujube’s whole growth period, WJBM had the strongest soil water-holdingcapacity among3coverage measures. The water storage capacity of WJBM was39.04%higher than CC in the0~70cm soil layer. Soil water storage of WCC is relatively low, and itswater retention effect was the worst. The rank of soil water storage in the0~70cm soil layerunder different treatments were: WJBM>JBM+SWC>CC>WCC. The soil water content indeep layer was significantly higher than the surfacial soil water content. Comparing with thesurface soil water content, the deep soil water content under WJBM, JBM+SWC, WCC, andCC treatments increased by20%,4.6%,15.3%and17.1%, respectively.. By analyzing theaverage soil moisture of each month under different treatments in0~70cm soil layer, wefound WJBM treatment had the strongest soil water-holding capacity and was significantlydifferent from JBM+SWC, WCC and CC treatments (P<0.01). The rank of soil water-holdingcapacity under different treatments was: WJBM>JBM+SWC>CC>WCC. From April to October, the growth of clover was different in various periods, thus the soil water-holdingcapacity of WCC treatment also changed. From this test, we found that clover consumed alarge amount of soil moisture, which caused soil drying. For WJBM treatment, the coveringlayer reduced soil moisture evaporation, made the surfaceform a virtual deep loose aquifer,produced less runoff, and improved soil infiltration capability.3. During the whole growing period of jujubes, vegetation cover and jujube branchmulching performed well on temperature control, which was obviously demonstrated under arelatively low temperature. These methods effectively reduced heat disperse, for keeping thesoil temperature in a relatively high temperature; when the temperature was high, thesemethodologies decreased the soil temperature by reducing sun radioactivity,for stopping thesoil evaporation to reduce soil temperature. In general, the optimum temperature for jujubes’growth was7℃～20℃, the root of jujubes started to grow at5.4℃, therefore, vegetationcover and jujube branch mulching promoted the growth of the root; In July, when the fruitsstarted to expand, the temperature was high, the evaporation of soil was huge, especiallywhen the temperature was higher than25℃, not only the water could be easily evaporated,but also the root of the fruit would also stop growing after CC treatment, the temperature of15cm soil could reach20℃during the day time, obviously, it was harmful to the growth ofjujube, and vegetation cover and jujube branch mulching properly resolved this issue.4. Air temperature，wind speed, and solar radiation were the three main ambient factorsinfluencing the soil temperature, they were significant correlationed to soil temperature.Under the same ambient condition, the influence of different mulch practice on soiltemperature was attributed to the soil porosity and soil moisture. The tendency of soiltemperature was closely relative to the tendency of soil moisture, which showed negativecorrelation with soil temperature. The soil water and temperature were highly coupled, soilmoisture influenced the soil thermal capacity and conductivity, as well as soil temperature.The soil temperature also influenced soil water movement. Mulching altered the radiationbalance and thermal conductivity of the system, as well as the soil moisture. This studyverified a significant negative correlation between the soil temperature and soil moisturecontent, the correlation coefficient of soil water storage and soil temperature was-0.741,which may be attributed to the difference of soil thermal conductivity relating to soil moistureof different mulching treatments.