Relationships between crop evapotranspiration (ET) and soil water content (SWC) have been studied worldwide. However, traditional data processing has drawbacks in modeling the contribution of SWC to ET on a layer-to-layer basis. To address this issue, large-scale weighing lysimeters were used to monitor the real-time ET along with Insentek sensors to monitor daily SWC dynamics of summer maize at Xuchang Experimental Irrigation Station, North China Plain, in 2016 and 2017. At the vegetative stage of maize (V6 and V12), roots reached 70 cm deep, with an average root length density (RLD) of 0.55 cm cm⁻³. Mean RLD at reproductive stage (VT and R3) was 1.13 cm cm⁻³, and the roots reached 100 cm deep. Cumulative percentage of ET_i to ET in topsoil (0–30 cm) was from 66% (V6) to 77% (R3), with the lowest proportion of 62% at maturity (R6), indicating > 2/3 of root mass distributed in the 0–30 cm soil layer. Principal component analysis was conducted to extract principal components of SWC. Soil moisture in the top (0–30 cm), middle (30–60 cm), and deep (60–100 cm) soil layers explained 8%, 14%, and 31% of the variances in ET (P < 0.05). Positive linear correlation was observed between ET and SWC in top and middle layers, while SWC in deep layer showed negative relationship with ET, which was mainly due to the gravitational forces acting on it. These findings support the premise that SWC in deep soil layer also has important effects on ET.

中文翻译：

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华北平原土壤水分对玉米蒸散量影响的结构方程模型

全世界已经研究了作物蒸散量（ET）和土壤水分（SWC）之间的关系。但是，传统的数据处理在按层对SWC对ET的贡献进行建模方面存在缺陷。为了解决这个问题，在2016年和2017年，在华北平原许昌实验灌溉站，使用大型称重测力计和Insentek传感器来监测实时玉米ET，以监测夏季玉米的每日SWC动态。玉米（V6和V12）的根深达70 cm，平均根长密度（RLD）为0.55 cm cm ^-3。生殖阶段（VT和R3）的平均RLD为1.13 cm cm ^-3，根部达到100 cm深。ET _i的累计百分比表土（0–30 cm）中ET的比例从66％（V6）增至77％（R3），在成熟期（R6）的比例最低，为62％，表明> 2/3的根质量分布在0– 30厘米土壤层。进行主成分分析以提取SWC的主成分。上层（0–30 cm），中层（30–60 cm）和深层（60–100 cm）的土壤湿度解释了ET差异的8％，14％和31％（P  <0.05） 。上层和中层的ET与SWC之间呈正线性相关，而深层的SWC与ET呈负相关，这主要是由于重力作用。这些发现支持了这样一个前提，即深层土壤中的SWC对ET也具有重要影响。