Automatic irrigation system based on dual crop coefficient, soil and plant water status for Vitis vinifera (cv Godello and cv Mencía)

• SIMDual-Kc obtained a good fit for Kcb ini, Kcb mid and Kcb end, for both cultivars.
• Soil evaporation (E) was about 51–64% of the water use during the crop season.
• Soil–plant water measures relations were determined: TDR & LWP and TDR & GMS.
• GMS permit establishing a threshold value related with leaf water potential.

This research aims at testing an automatic control irrigation system, using a wireless sensor network, in traditional Galician vineyards of Vitis vinifera (L.) cv. ‘Godello’ and cv. ‘Mencía’ to determine the threshold values of soil water potential at which plant stress begins, calibrating crop coefficients, building soil–water characteristics curves and measuring plant water status. In the cv. ‘Godello’ trial, rain-fed and two irrigations systems (surface and subsurface drip irrigation) were conducted over two growing seasons (2012–2013); during the same seasons cv ‘Mencía’ was also studied, but only under rain-fed conditions. The SIMDualKc model, which estimates soil water balance by means of the dual Kc approach, was used to estimate crop evapotranspiration (ETc) by calibrating the full basal crop coefficient for the vine and cover crop (Kcb full), which represents the transpiration component of ETc, and a soil evaporation coefficient (Ke). The model was calibrated and validated by comparing model simulations with TDR observed soil water content data. Granular matrix sensor (GMS) was linked in a wireless sensor network; soil water potential measured with GMS, was used to correlate with TDR data. Leaf water potentials (LWP) – midday and stem – allowed us to obtain plant water status. A good fit was obtained between SIMDualKc model and TDR (r2 > 0.74), TDR and LWP (r2 > 0.65), TDR and GMS (r2 > 0.81), showing that continuous measures with GMS permit establishing a threshold value related with leaf water potential (midday or stem). For both cultivars, the threshold was Ψsoil = −0.1 MPa. The process applied in this study proved to be useful for managing water in real-time in a vineyard; triggering the irrigation system when the threshold value was reached.