Simulation Of Water Productivity And Deep Layer Soil Water And Nutrient Characteristics Of Rainfed Apple Orchards In Central Areas Of Loess Plateau

The Loess Plateau has become the biggest apple planting predominant region of Chinawith the biggest planting areas and yields. Due to the inappropriate planting density designand fertilizers input, apple production faces the problem of unsustainable development infuture. By measuring and analyzing the soil water and nutrient contents of typical rainfedapple orchards and long-term simulation study of apple water productivity, it is expected toexplore the long term response of soil water and nutrients of rainfed apple orchards, find theinteraction principles among soil water and nutrients variation, apple planting and water andfertilization managements, and finally determine the reasonable planting density andfertilization in apple orchards on the Loess Plateau.The study measured deep layer soil water and nutrient contents of different year-oldrainfed apple orchards at typical apple planting areas of Luochuan, Changwu and Xifeng inthe semi humid and arid loess highland zone of the Loess Plateau, analyzed the variationpatterns of soil water contents, its desiccation and soil nutrient （mainly nitrogen, phosphorusand potassium） contents; By using WinEPIC crop simulation tool, the study separatelysimulated the long-term （45years） variation of apple yields and soil deep layer desiccationunder different planting densities and different levels of fertilizer treatments, analyzed thedistribution and formation of soil deep layer desiccation, finally proposed the appropriateplanting densities, fertilizer levels and the renewing years of apple orchards at each sites.（1） About water contents varying: during the depth0^-1500cm of13typical appleorchards at three sites （Luochuan, Changwu and Xifeng）, the average soil water contents, soilwater storage, soil available water storage, over used water storage and annual soil desiccationrate were13.60%,2652.64mm,752.23mm,390.21mm and23.08mm·a^-1, respectively. Thethickness of stable desiccated soil layers at each sites were620cm,830cm and750cmrespectively and the soil average water contents were13.28%,12.34%and10.92%,respectively. Factors that affected soil water content and desiccated layer development weresupplement irrigation, tree age, planting density, regional precipitation and landform etc.（2） During the soil depth0^-100cm，the average soil organic matter contents at three sites（Luochuan, Changwu and Xifeng） showed relatively insufficiency as whole, the averagenitrogen contents showed insufficiency at Luochuan, normal at both Changwu and Xifeng;The average available phosphorus contents showed normal at Luochuan, rich at bothChangwu and Xifeng; the average available potassium contents showed normal and close torich at Luochuan, rich in all the orchards at both Changwu and Xifeng. Soil organic matter,nitrogen, phosphorus contents at all the three sites showed enrichment in the upper soil layers(0^-100cm) and insufficiency in lower soil layers （100-300cm） relatively, however, for soilpotassium contents （for both total potassium and available potassium） varying in both theupper and lower soil layers showed no significant diversity. Advice for fertilization management: for all the three sites, it is suggested that much more soil organic fertilizer andnitrogen fertilizer should be used and both nitrogen and phosphorus should be used in deepersoil layers according to the very actual conditions, but less or no potassium fertilizer shouldbe used.（3） The study established the WinEPIC meteorological data base, soil data base and crop（apple） parameter data base by field observation, measurement and data collection. Thevalidation of WinEPIC application for apple orchards water productivity and soil watervariation showed that WinEPIC could be applied for related study in the rainfed appleorchards at Luochuan, Changwu and Xifeng in the semi humid and arid loess highland zoneof the Loess Plateau.The simulating results indicated that the optimum planting density and fertilizationtreatment for rainfed apple orchards at each site:1) Luochuan: density should be1143plants·hm^-2（2.5m×3.5m）, fertilizer management: nitrogen fertilizer （N）300kg·hm^-2,phosphorus （P5O2）150kg·hm^-2, potassium fertilizer （K₂O）90kg·hm^-2; appropriate renewingperiod of apple orchard should be less than21years).2) Changwu: density should be1000plants·hm^-2（2.5m×4m）, fertilizer management: nitrogen fertilizer （N）100kg·hm^-2,phosphorus （P5O2）50kg·hm^-2, potassium fertilizer （K₂O）30kg·hm^-2; appropriate renewingperiod of apple orchard should be less than19years).1) Luochuan: density should be1000plants·hm^-2（2.5m×4m）, fertilizer management: nitrogen fertilizer （N）400kg·hm^-2,phosphorus （P5O2）200kg·hm^-2, potassium fertilizer （K₂O）120kg·hm^-2; appropriate renewingperiod of apple orchard should be less than18years).