Insentek Sensor: An Alternative to Estimate Daily Crop Evapotranspiration for Maize Plants

Abstract

Estimation of ground-truth daily evapotranspiration (ETc) is very useful for developing sustainable water resource strategies, particularly in the North China Plain (NCP) with limited water supplies. Weighing lysimetry is a well-known approach for measuring actual ETc. Here, we introduced an alternative to lysimetry for ETc determination using Insentek sensors. A comparison experiment was conducted for maize plants at Xuchang Irrigation Experiment Station, in the NCP, in 2015 and 2016. Insentek ETc was evaluated using data on clear days and rainy days independently. We found that daily ETc increased gradually from VE (emergence) to VT (tasseling) stages, peaked at the R1 (silking) stage with the highest value of 7.8 mm·d−1, and then declined until maturity. On average, cumulative total of lysimetric ETc was 19% higher than that of Insentek ETc. The major depth of soil water extraction might be 60 cm for maize plants on lysimeters according to soil water depletion depth monitored by Insentek sensors. Daily ETc significantly related to soil water content (SWC) in topsoil (0–30 cm) in an exponential function (coefficients of determination (R2) = 0.32–0.53), and to precipitation (Pre) in a power function (R2 = 0.84–0.87). The combined SWC (0–30 cm)–Pre–ETc model may offer significant potential for accurate estimation of maize ETc in semi-humid environment of the NCP.