Soil Hydrological Characteristics And Water Productivity Simulation Of Apple Forest In The Hilly-Gully Region Of Loess Plateau

Soil water content,soil nutrient,soil hydrological,and evapotranspiration were measured and crop water productivity of apple forest were simulated in this study to reveal the variation characteristics of soil water in rainfed orchard and promote the sustainable development of apple industry in the hilly-gully region of Loess Plateau.On the basis of field investigation and field observations of yield,soil water and soil nutrients in the deep layers of apple forest,this project analyzed the soil drying state and water productivity characteristics of apple forest under different cultivation and different topography conditions,soil nutrient status and variations in the 0³00 cm soil layer of the profile in the different aged apple orchards,and the evapotranspiration characteristics of apple orchard.Morever,the WinEPIC model developed by USA was used to simulate apple output,the dynamics of the deep soil water content and water productivity of dryland apple orchards in Mizhi during 2001²015.The main conclusions were as follows:?1?There were different degrees of dried soil state in different aged apple forest in this region.The soil layes under 100 cm of apple forests showed intense dried in the full bearing period and the decline phase.The soil water storage in 0⁶00 cm soil layer of young apple forest was significantly higher than the full bearing period and the decline phase?P<0.05?.The soil water content in the deep layer was gradually decreased,the soil dried layer thickness was deepened,and the speed of soil desiccation formation was slowed down with the increasing age of apple forest.The dynamics of water productivity and soil water indicated that the depth of soil water depletion in the full bearing period of apple forest was deeper than the rain replenishment,while it is opposite in the young and decline phase of apple orchards.The average output was 5.6³7.5×103 kg hm^-2 in the different aged apple orchards forest,and it increased firstly and then decreased with the increasing age.The crop water productivity was significantly higher in the apple forest of the full bearing period than in the young apple forest?P<0.05?.In a word,the available life of apple orchard was 25³0a in this region.?2?The analyzed results of the characteristics of the soil water content in apple forest under different site conditions showed that:the soil water storage in 0⁶00 cm soil profile of orchard in terrace was the largest,followed by the slope,corresponding to 882.1,645.2 mm,respectively.Soil water content in shallow soil layer?0²00 cm?for the two fields showed medium variation,ranked in the order of slope orchard>terrace orchard.There was no significant difference of the variation of soil water content in different terrain orchards in deep soil layer?200⁶00 cm?,and soil water content was relatively stable.The depth of soil water depletion in slope orchard was greater than that the rain replenishment,while it is opposite in terraced orchard.Soil desiccation in terraced orchard occurred seasonally,and a temporary dried soil layer formed in the shallow soil layer in the case of soil water shortage,and there was no permanent dried soil layer.There was a seasonal dried layer in the slope orchard in 0²00 cm soil layer,and the dried soil layer of 200³00 cm in slope orchard is permanent and the thickness of dried layer was 100 cm.?3?The status of the soil nutrient along the soil profiles in different cultivated orchards showed as follows:The content of organic matter,total nitrogen and alkaline nitrogen in the0³00 cm soil layers of the orchards was falling down to the level and they were all extreme deficiency,which was less than 6 g kg^-1?0.5 g kg^-1and 30 mg kg^-1,respectively.The content of total phosphorous and available phosphorous varied in the range of 5.4⁶.5 g kg^-1 and4.56¹1.86 mg kg^-1,respectively,and it indicated that they were both moderate or minor deficiency.The content of available potassium was moderate in nutrient availability level,and it ranges from 71.98 to 119.68 mg kg^-1.In the orchards of young apple trees,soil water content was closely related to soil organic matter,total nitrogen and alkaline nitrogen contents,whereas it was opposite in the full bearing period and decline phase.It indicates that in the former the soil water regime was well preserved and in the latter the soil water environment deteriorated,with severe or intense soil desiccation occurring in deep soil layers.Therefore,there should be soil water conservation measurements in different aged apple orchards,and an improvement in fertilization should be made,such as pay more attention to application of organic manure and nitrogen fertilizer,the application of phosphorous fertilizer should be increased properly,and reduce or even stopp use potassium fertilizer.We should pay more attention to the soil desiccation rather than the issue of nutrient imbalance caused by soil drought.?4?A thermal dissipation probe?TDP?and micro-lysimeter were used to measure various components of evapotranspiration such as plant transpiration,soil evaporation,and use water balance principle to calculate canopy interception.This study analyzed the relationship between meteorological factors and transpiration rate,evaluated condition of the soil water balance of7-years apple orchard.The purpose was to understand correctly and evaluate the eco-hydrological effect of apple orchard.The results showed that the average daily transpiration rate in different growth periods ranked in the order of fruit growth period>fruit coloring stage>new shoots growth and young fruit growth period>germination and flowering period.The time of peak which the transpiration rate reached at different growth stages was different at the hour scale.Under different weather conditions,the main meteorological factors affecting the transpiration rate of apple orchard were solar radiation and air temperature,and the transpiration in sunny days were significantly larger than that of the rainy days.The main periods of water consumption of apple trees were fruit growth period and fruit coloring period.Precipitation shows significant lagging effect on transpiration.According to the principle of soil water balance,the contribution of the three components to evapotranspiration in the apple forestland ranked in the order of plant transpiration>soil evaporation>canopy interception,which accounted for 58.9%,26.8%and 14.3%to evapotranspiration,respectively.During the experiment period,the precipitation was more than the evapotranspiration,and the water of apple orchard was surplus and it was different in different month.The water management of apple orchard should be strengthened in germination and flowering period,new shoots growth and young fruit growth period.?5?The model validation results of apple output and soil water content of dryland apple orchards in Mizhi showed as follows:the simulated results of apple yield and dynamic change of soil water content for dryland apple orchards were relatively precise.The WinEPIC with parameter modification could be used in the rainfed apple orchards in Mizhi region.During2001²015,the average output of the young orchard was 14.5 t hm^-2,the mature orchard?10¹5a?was 26.7 t hm^-2,the average yield was 20.1 t hm^-2.The annual evapotranspiration of forest had the tendency that decrease first,then increase,and fluctuate steady at last,which was closely related to the annual precipitation.The crop water productivity increased with the increasing age of apple tree,and the water productivity in mature forest was significantly greater than that of young forest.The effective soil water storage decreased with the increasing age of apple tree age.The simulated results showed that the dried soil layer was 100²00 cm layer,and the thickness of dried layer increased along with the increasing age of apple trees.