Sustainability and environmental assessment of fertigation in an intensive olive grove under Mediterranean conditions

Water and nitrogen surpluses are major concern for the new intensive olive groves in South of Portugal. In this study, field measurements were integrated with a system model, Root Zone Water Quality Model (RZWQM2) to assess the sustainability and environmental impact of fertigation in an intensive olive grove (Olea europaea L. var. Arbequina). The model provided acceptable predictions of evapotranspiration, soil moisture and nitrate contents. Based on model simulations, under current fertigation practices, 57% of the irrigation applied was lost via drainage, while 71% and 5% of fertilizer N inputs were lost through leaching and denitrification, respectively. The non-fertilizer N input from soil organic matter (OM) satisfied 64% of the crop N needs. The tested model was used to predict the impacts of a full irrigation (FIFC) and two regulated deficit irrigation schemes (RDI75, RDI50) on drainage and N leaching. In FIFC the atmospheric demand was met while the application frequency maintained the water storage below the soil field capacity. In RDI75 and RDI50 the irrigation application amount between stone hardening and onset of ripening was 75 and 50% of FIFC respectively.