Estimating evapotranspiration by capacitance and neutron probes in a drip-irrigated apricot orchard

This paper describes how a neutron probe (NP) and a multi sensor capacitance probe (MCP) can be used for monitoring the soil water content in order to develop a soil water balance and to estimate the evapotranspiration (ETc) of an apricot (Prunus armeniaca L.) crop. The van Genuchten model was applied to estimate water drainage below the active root zone, based on the measurements from both devices. Average crop evapotranspiration (ETc), estimated from the soil water balance for the whole period (17 months), was 1.6 and 1.5mm/day for NP and MCP respectively, while the crop evapotranspiration calculated by the Penman-Monteith method (ETc-FAO) was 2.3mm/day. Drainage measured by both devices was negligible. The ETc measured by MCP was better correlated with the ETc measured by FAO methodology than with that corresponding to NP A good correlation between the ETc values measured by NP and MCP was found However MCP permits continuous recording of the soil water content, is cheaper and less dangerous, while NP produces more accurate measurements than MCP.