蓄水坑灌下矮砧苹果园水分监测点位置研究

Monitoring Locations of Soil Water Content in Water Storage Pit Irrigated Dwarfing Apple Tree Orchard

以蓄水坑灌（坑深40 cm）下的5 a生矮砧富士苹果树为研究对象,通过田间测定直径小于等于2 mm的吸水根分布和不同位置的土壤含水率情况,采用数据拟合和聚类分析的方法,探讨蓄水坑灌下矮砧苹果树土壤水分监测点的合理布置。结果表明：1蓄水坑灌下,苹果树吸水根在水平方向上主要分布于距树干0～90 cm范围内,其根长密度占总根系的90%以上;垂直深度上主要分布于距地表0～120 cm深度范围内,其根长密度占总根系的80%以上,并在40～60 cm深度达到生长峰值,其根长密度占总根系的40%以上。2以Dr90（距离树干90 cm,深度0～120 cm）监测点为含水率分析区域,通过水分分布曲线拟合和聚类分析得出,Dr90监测点60 cm深度处的含水率可代表整个0～120 cm深度剖面的含水率情况,并利用2013年的实测数据进行验证,含水率相对误差在±5%范围内。

Soil water content（ SWC） is of great importance to establish an appropriate irrigation scheme.The study object is 5-year-old dwarf apple trees under water storage pit irrigation method（ depth 40 cm）.In order to find an optimal SWC monitoring location,the distribution of apple tree fine roots（ d≤2 mm）at different locations and SWCs within the root zone were studied and analyzed with regression and cluster analysis methods. The results showed that over 90% fine roots of apple tree were within 0 ～ 90 cm from the apple tree trunk in horizontal direction,while over 80% fine roots were within 0 ～ 120 cm from the apple tree trunk in vertical direction. The growth peak of fine roots was within 40 ～ 60 cm depth which accounted for over 40% of total fine roots. Meanwhile,the monitoring points were located at 90 cm away from the trunk（ Dr90）. SWC distribution in vertical direction of the Dr90 monitoring points was accorded with exponential function,with correlation coefficient greater than 0. 8. Through sorting the SWC at six different depths in Dr90 with R type hierarchical clustering method,it showed that the soil moisture sensors in 60 cm can be used to represent the SWC condition within 0 ～ 120 cm depth. The SWC error between the simulations and observations in 2013 was within ± 5%. The experimental results suggested that the profile（ depth 60 cm） of SWC measured in the Dr90 was sufficient to estimate the water consumption amount under the water storage pit irrigation in the orchard.