陕北黄土丘陵区山地苹果园的土壤水分动态研究

掌握土壤水分特征是实现果园科学管理、有限雨水资源合理高效利用、保证果树高产优质的关键。以陕北米脂山地6年生红富士苹果园为研究对象,于2015年4月—2016年6月采用FDR、中子水分仪和烘干法相结合的土壤水分监测方法,分析了山地苹果园的土壤水分总体特征、单株不同位点的水分动态以及不同旱作措施(秸秆覆盖、起垄覆膜垄沟集雨、有机肥覆盖)的土壤水分环境效应。结果表明:陕北山地果园时段干旱严重,最严重的为苹果树新梢生长和幼果发育期;春季土壤干旱程度取决于上年入冬前土壤储水量高低。果园0~60 cm土层(根系分布集中层)水分随降雨量而变化,表现为较一致的季节变化特征;土壤水分的变化滞后于降雨变化,且降雨对土壤水分的影响随土层加深而减弱,100 cm深土层受降雨影响减弱,土壤剖面200 cm以下土层土壤含水量保持相对稳定。6年生山地苹果园土壤已经出现干化现象,且在90~300 cm存在明显的低湿层,土壤体积含水量常年处在12%以下。苹果树单株尺度范围内,土壤含水量随距树干距离增加单调递增;土壤水分的平均值处在距树干105 cm处;沿行向距树干不同距离位点的土壤含水量显著高于沿株向距树干等距离位点的含水量(P0.05)。秸秆覆盖、起垄覆膜垄沟集雨和有机肥覆盖措施相较于空白对照(不覆盖、不灌溉)均能有效改善土壤水分环境,缓解果树生育期内水分供需矛盾,其中起垄覆膜垄沟集雨措施的保墒效果最佳,建议陕北黄土丘陵区山地雨养苹果园采用起垄覆膜垄沟集雨的保墒措施。

Soil moisture dynamics of apple orchards in Loess Hilly Area of northern Shaanxi Province

Knowledge on the variation in soil moisture is critical for the scientific management of orchards, the efficient utili-zation of limited rainfall and the improvement of fruit production and fruit quality. In this study, a comprehensive soil mois-ture monitoring method was used in combination with FDR, neutron moisture meter and oven-drying to determine the general characteristics of soil moisture in loess hilly apple orchards of northern Shaanxi Province. Also the variation in soil moisture at different sampling sites around orchard trees and the environmental effects of different dry-farming measures (e.g., straw mulching, ridge film mulching with furrow rainwater harvesting and organic fertilizer mulching) were investigated in 6-year-old 'Fuji' apple orchard for the period from April 2015 to June 2016 in Mizhi County in Shaanxi Province. The results showed that seasonal drought was quite severe, especially during the shoot growth and young fruit development stages. The degree of soil drought in spring was highly dependent on soil water storage in the last winter. Soil moisture in the 0-60 cm soil layer (root-zone layer) varied with rainfall and had seasonal variation characteristics, but lagged behind that of rainfall. The effect of rainfall on the variation of soil moisture weakened with increasing soil depth. Soil moisture in soil layer below 200 cm was relatively stable, but soil desiccation occurred in 6-year-old apple orchard in the hilly region. There was an obvious low humidity layer in the 90–300 cm soil, where volumetric soil water content was less than 12% for the whole year. Soil moisture increased with increased sampling distance from apple tree. While the regression equations of soil moisture between apple plants and between apple tree rows (y) with distance to apple tree were respectivelyy = 0.0105x + 6.8702 (R2= 0.9966) andy = 0.014x + 7.6912 (R2= 0.9827), the mean soil moisture for the sites was closest to the one 105 cm away from the tree Soil moisture at different sites from tree between rows was significantly higher than that at equivalent distance between plants (P< 0.05). Compared with CK (no mulching or irrigation), dry-farming measures such as the straw mulching, ridge film mulching and furrow rainwater harvesting and organic fertilizer mulching effectively improved soil moisture environment. To a certain extent, these dry-farming measures were recommended for dealing with the issue of soil water supply and demand, especially during plant growing season. Among the measures, ridge film mulching and furrow rainwater harvesting had the highest degree of preservation of soil moisture. Thus ridge film mulching and furrow rainwater harvesting was recommended as the most effective agricultural measure in preserving soil moisture in rainfed apple orchards in Loess Hilly Areas of north-ern Shaanxi Province.