The Formation Mechnisim And Control Technique Of Deep Soil Desiccation Of Apple Orchard On The Weibei Highland

Weibei Dryland is of high quality for the apple production,with the favourable conditions of high elevation,adequate illumination and far away from industrial district.Due to the relatively low precipitation and its maldistribution as well as local unreasonable orchard management,leading to water overuse in orchard,sealing of soil,decline of soil fertility and imbalance soil nutrient,which has restricted the high efficient development of the apple yield and quality.By measuring the soil water and long-term simulation study of orchard water productivity of representative rainfed orchard on Weibei Dryland,revealing the variation characteristics of soil water in rainfed orchard,promoting the sustainable development of apple industry in Weibei Dryland.The study measured deep soil water of different year-old rainfed apple orchards at typical apple planting zone of Luochuan,Baishui,Changwu and Yanan on the Weibei Dryland,analyzed deep soil desiccation process and regional distribution of the rainfed orchard.In order to study the response of water productivity in dryland orchards under manure and fertilization as well as irrigation,the paper referred to the analysis of long-term orchard yield,water consumption,water stress,soil water and soil moisture distribution at Luochuan and Changwu in Weibei Dryland,pursing reasonable ratio of manure and chemical fertilization as well as amount of irrigation,providing technical support to improve water productivity of rainfed orchard.The main achievements were showed as following:(1)The average soil moisture in 0-1500 cm soil layer of Luochuan,Changwu,Baishui and Yanan were 13.90%?15.53%?12.77% and 7.95%,the average soil available water storage were 1151.5?1371.0?734.9and 184.5 mm,it showed that the soil moisture and soil available water storage declined as the decrease of precipitation.Supplement irrigation,tree age,planting density and geomorphic type were the factors that affected soil moisture and desiccation degree.Soil desiccation index of the 4 area were 29.41%?25.28%?46.16% and 83.52%,ranking medium desiccation,medium desiccation,medium desiccation and strong desiccation,soil desiccation of orchards aggravated as the decrease of regional precipitation.(2)During the simulation study period of 1965-2009,as the age of tree increasing,the orchard yield shows a trend that increasing rapidly in the early stage and reducing fluctuatedly later,meanwhile,the soil moisture content shows a fluctuant downward trend and soil organic carbon content reveals an increasing tendency.Under different fertilization treatments,the soil water content had a significant negative correlation with the orchard land use age,on the contrary,there was a positive correlation between the soil organic carbon content and the orchard land use age,furthermore,the two coefficients of correlation became large with the increasing application proportion of organic manure.Compared with single fertilizer application,the other 5 organic mature fertilize treatments are all favorable for the increase of soil moisture content and soil organic carbon content,and the 3 treatments of M1-M3 could improve the apple orchard yields in some degree.Considering from the effective soil water content in 0-15 m soil layer and simulated orchard yields aging from 4 to 45,the appropriate proportion between organic manure and fertilizer for Luochuan apple orchard is among 2:3~3:2.(3)During simulation of different irrigation,yield of orchard in Luochuan and Changwu tended to increase in the early growth stage,maintaining in high level volatility for 5 years,and gradually decrease and keep in some yield level.Both of average yield of I4 were the highest yield in the test point,they were 34.48 t/hm2 and 29.99 t/hm2,respectively.In this study,yield in the orchard improved as the increase of irrigation amount.Difference of yield among the different irrigation treatment increased gradually in the early growth stage until 25 years old of orchards,then the yield difference among treatment decreased,until the late growth stage the difference disappeared.During the 45 years simulation of soil available water,it showed the trend of reduction with fluctuation both in Luochuan and Changwu.In the early growth,for the water consumption in the orchards was relatively smaller,soil available water could maintain at a high level.Along with the tree growth and maturity,the water consumption of apple tree increased,the soil available water decreased quickly and the slowed down.Irrigation had an obvious effect on soil available water in the early stage,the soil available water improved with the increase of irrigation amount.As the irrigation amount increased,the soil dry layer occurred later,and its thickening slowed down.For the comprehensive consideration of yield,water stress days,soil available water and soil moisture distribution,the reasonable irrigation amount of rainfed orchard in Luochuan and Changwu were 800m3/hm2~1600m3/hm2 and 1600~2400m3/hm2.(4)Based on the soil water storage recovery quantity and soil dry layer recovery thickness,it could be estimated that how many years it needs to recovery the soil moisture of orchard to the level of local cropland.It was estimated that the 26 years old orchard in Luochuan needed 5 year,the 27 years old orchard in Changwu needed 8 year,the 23 years old orchard in Baishui needed 9 year.It showed that the year of soil water recovery tended to be more as the decrease of precipitation.And there were two form of soil dry layer recovery characteristic,which were from top to bottom and from bottom to top.That characteristic was affected by the precipitation,soil texture and deep soil water running.