当前位置: X-MOL 学术Irrig. Sci. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Resolving discrepancies between laboratory-determined field capacity values and field water content observations: implications for irrigation management
Irrigation Science ( IF 3 ) Pub Date : 2019-07-09 , DOI: 10.1007/s00271-019-00644-4
Steven R. Evett , Kenneth C. Stone , Robert C. Schwartz , Susan A. O’Shaughnessy , Paul D. Colaizzi , Scott K. Anderson , David J. Anderson

The concept of soil water contents at field capacity (FC at 0.33 MPa) and at wilting point (WP at 15 MPa) is often used to explain plant water availability and as maximal and minimal limits on observed soil water content. Field observations often differ, however, from laboratory-determined FC and WP water content values. Moreover, as more capable sensors have become available and graphical plots of soil water dynamics have become common, plotting of FC and WP lines on such graphs often reinforces these differences and engenders confusion rather than enlightenment. Resolving this confusion has been greatly eased by the introduction of soil water sensors that encapsulate an entire time domain reflectometry (TDR) system in individual sensor heads and the recent availability of a reader for capturing georeferenced values of the TDR waveform and estimated values of soil volumetric water content (VWC), permittivity, temperature, and bulk electrical conductivity. The present study illustrates the typical confusion with season-long graphs of soil water content that greatly exceed the FC values for individual soil horizons, and it resolves the confusion with concurrent and co-located TDR sensor readings and volumetric soil sampling to ascertain sensor accuracy. It was found that sensor readings were reasonably accurate (RMSE = 0.01 m3 m−3) across a range of textures from fine sandy loam to clay, even though some measurements were up to 0.19 m3 m−3 larger than FC values. Water contents in a sandy eluviated horizon above a dense clay were larger than FC due to the clay layer impeding water flow and perching water in the sand, augmented by the capillary fringe in the fine sand. Confusion was in part created by plotting water content for four different depths of different textures but plotting the FC and WP values for only one soil texture. Misperception of water available for crops was greatly reduced by converting the water content values to equivalent water depth values for the four soil layers and plotting only the soil water storage depth for the entire profile depth covered by the sensing network. The ambiguity was further reduced by determining the maximum value of soil water storage for the season and calculating soil water depletion by subtracting the maximum value from the soil water storage throughout the season. When this was done, it was easy to see depths of water removed from the soil and needing replacement, and to see the extra soil water depletion that occurred when a plot was not irrigated.

中文翻译:

解决实验室确定的田间容量值与田间含水量观测值之间的差异:对灌溉管理的影响

田间持水量(FC 为 0.33 MPa)和枯萎点(WP 为 15 MPa)的土壤含水量的概念通常用于解释植物水分可用性,并作为观察到的土壤含水量的最大和最小限制。然而,现场观察通常与实验室确定的 FC 和 WP 含水量值不同。此外,随着功能更强大的传感器的出现和土壤水动力学图形变得普遍,在此类图形上绘制 FC 和 WP 线通常会强化这些差异并导致混淆而不是启蒙。通过引入将整个时域反射计 (TDR) 系统封装在单个传感器头中的土壤水分传感器,以及最近用于捕获 TDR 波形的地理参考值和土壤体积估计值的读取器的可用性,大大缓解了这种混淆。水含量 (VWC)、介电常数、温度和体积电导率。本研究说明了土壤含水量的季节性图表的典型混淆,这些图表大大超过了单个土壤层的 FC 值,它解决了并发和共同定位 TDR 传感器读数和体积土壤采样以确定传感器精度的混淆。发现传感器读数相当准确(RMSE = 0.01 m3 m-3),涵盖从细砂壤土到粘土的一系列质地,即使某些测量值比 FC 值大 0.19 m3 m-3。由于粘土层阻碍水流和滞留在砂中的水,在细砂中的毛细管边缘增加了致密粘土上方的砂质冲积层中的含水量大于 FC。混淆的部分原因是绘制了四种不同深度的不同质地的含水量,但只绘制了一种土壤质地的 FC 和 WP 值。通过将含水量值转换为四个土层的等效水深值,并仅绘制传感网络覆盖的整个剖面深度的土壤蓄水深度,大大减少了对作物可用水的误解。通过确定当季土壤蓄水量的最大值并通过从整个季节的土壤蓄水量中减去最大值来计算土壤水分耗竭,进一步减少了歧义。完成此操作后,很容易看到从土壤中去除和需要更换的深度水,以及在未灌溉地块时发生的额外土壤水分耗竭。
更新日期:2019-07-09
down
wechat
bug