Abstract
While traditional soil water sensors measure soil water content (SWC) at point scale, the actively heated fiber-optics (AHFO) sensor measures the SWC at field scale. This study compared the performance of a distributed (e.g., AHFO) and a point-based sensor on closing the field water balance and estimating the evapotranspiration (ET). Both sensors failed to close the water balance and produced larger errors in estimated ET (ETε), particularly for longer time periods with >60 mm change in soil water storage (ΔSWS), and this was attributed to a lack of SWC measurements from deeper layers (>0.24 m). Performance of the two sensors was different when only the periods of ˂60 mm ΔSWS were considered; significantly lower residual of the water balance (Re) and ETε of the distributed sensor showed that it could capture the small-scale spatial variability of SWC that the point-based sensor missed during wet (70–104 mm SWS) periods of ˂60 mm ΔSWS. Overall, this study showed the potential of the distributed sensor to provide a more accurate value of SWS at field scale and to reduce the errors in water balance for shorter wet periods. It is suggested to include SWC measurements from deeper layers to better evaluate the performance of the distributed sensor, especially for longer time periods of >60 mm ΔSWS, in future studies.
Highlights
Changes in soil water affect crop growth, grain yield and other ecological processes such as salinity, nutrient transformation, and emission of greenhouse gases (CO2, CH4 and, N2 O) from the soil.An accurate estimation of the ∆SWS is important for improving the field water balance closure, in addition to the measurements of other components of the water balance, such as precipitation and ET
The study site was a 4.2 ha experimental corn field located near Coteau-du-Lac, Québec, Canada (Figure 1a) approximately 60 km west of Montréal
The relationship between Tcum_N and soil water content (SWC) was stronger for all three depths
Summary
An accurate estimation of the ∆SWS is important for improving the field water balance closure, in addition to the measurements of other components of the water balance, such as precipitation and ET. Improving knowledge about the soil water balance at the field scale is important to be able to understand the hydrological processes necessary to optimize water management practices. ∆SWS can be determined directly using weighing lysimeters or soil water sensors. Weighing lysimeters are expensive and, accurate, are difficult to manage and afford little replication at the field scale. Traditional point-based soil water sensors such as TDR, and neutron or capacitance probes have been used to estimate ∆SWS and to improve the soil water balance estimations [2,3,4].
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