Can limits of plant available water be inferred from soil moisture distributions?

Abstract

AbstractRobust assessment of crop water availability requires effective integration of soil moisture data within the range of field capacity (θFC) to permanent wilting point (θPWP). Emerging needs for spatiotemporally dynamic θFC and θPWP are difficult to achieve with lab determinations. Therefore, we used long‐term data from 182 sites across the United States to evaluate whether soil moisture extremes defined by 95th and 5th percentiles represent θFC and θPWP, respectively. Soil moisture extremes and lab‐measured θFC and θPWP were well correlated (R2 = 0.71−0.92), however, both 95th and 5th percentiles overestimated θFC and θPWP at most depths (RMSE = 6%–16% vwc). Percentiles of soil moisture distribution that corresponded to lab‐determined θFC and θPWP varied widely and were a function of precipitation received at the site and site‐ and soil‐depth specific clay content. These findings imply that while θFC and θPWP may not be broadly represented by soil moisture extremes (95th and 5th percentiles), there may be potential to statistically infer the positioning of θFC and θPWP within long‐term soil moisture distributions using biophysical determinants such as aridity and soil characteristics.