Shallow water tables can contribute water for plant use; therefore, plant available water includes not only the water stored in the root zone, but also the water moving up from below the root zone. The purpose of this study was to quantify the amount of water moving upward to the root zone. Automated water content reflectometers were used to monitor soil water content across a landscape in Central Iowa, which had varying shallow water tables. Either manual or automated water table depths were measured. Tipping bucket raingage and eddy covariance evapotranspiration (ET) methods were used to measure rain and evapotranspiration as part of the water balance. Upward water movement ranges were determined from water balance and uncertainties for each component (rain, ET, change in soil water content). In 2006 out of 53 dry days (days that did not have any rain), 37, 43, and 46 d showed net upward flux for shoulder, backslope, and toeslope positions, shown by an uncertainty range that did not overlap zero. In 2007, 37 out of 62 dry days showed net upward flux for the toeslope position. The mean significant net upward flux for dry days was 2.6, 3.2, and 3.1 mm d super(-1) for the shoulder, backslope, and toeslope positions in 2006, and 2.5 mm d super(-1) for the toeslope position in 2007. Mean ET on nonrain days was 4.0 and 4.1 mm d super(-1) in 2006 and 2007. Automated equipment used to develop a water balance approach provided a quantitative approach to estimate net upward soil water flux in agricultural fields.
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机译：浅水位可为工厂用水提供水;因此，植物可用水不仅包括储存在根部区域的水，还包括从根部区域下方向上移动的水。这项研究的目的是量化向上移动到根部区域的水量。自动水含量反射计用于监测爱荷华州中部一个景观的土壤含水量，该景观的浅层水位各不相同。测量了手动或自动水位深度。倾倒式水桶集水和涡流协方差蒸散（ET）方法用于测量降雨和蒸散，这是水平衡的一部分。水分向上移动的范围由水分平衡和每种成分的不确定性（雨，ET，土壤含水量的变化）确定。在2006年的53个干旱天（无雨天）中，第37、43和46天显示肩部，后坡和前坡位置的净向上通量，其不确定性范围不为零。在2007年的62个干旱日中，有37个干旱日显示了坡脚位置的净向上通量。 2006年，干燥日的平均显着净向上通量在肩部，后坡和前坡位置分别为2.6、3.2和3.1 mm d super（-1），在2007年前后位置为2.5 mm d super（-1）。 。2006年和2007年非雨天的平均ET分别为4.0和4.1 mm d super（-1）。用于开发水平衡方法的自动化设备提供了一种定量方法，用于估算农田中土壤净向上的水通量。
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