Agricultural Water Management 146 (2014) 346–360 Contents lists available at ScienceDirect Agricultural Water Management jou rn al hom epage: www.elsevier.com/locat e/agwat Sustainability and environmental assessment of fertigation in an intensive olive grove under Mediterranean conditions M.R. Cameira a,∗ , A. Pereira a , L. Ahuja b , L. Ma b a Department of Biosystems Engineering, Superior Institute of Agronomy, University of Lisbon, Tapada da Ajuda, 1349-017 Lisbon, Portugal b USDA-ARS-NPA, Agricultural Systems Research Unit, Fort Collins, CO, USA a r t i c l e i n f o Article history: Received 28 December 2013 Accepted 4 September 2014 Keywords: Irrigation Olive grove System modeling RZWQM2 Water balance N leaching a b s t r a c t 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. Compared with the current practice, the FIFC decreased drainage and N leaching by 47% and 90% respectively, while maintaining the actual evapotranspiration (ETa). The RDI75 seems to be the most adequate for the studied agro-system since, in relation to the FIFC, it saved 13% of irrigation water with only 5% decrease in ETa. Furthermore, the 15% reduction in leaching, together with the 19% increase in soil OM mineralization optimized the trees N uptake. The study of three different N application rates for each irrigation scenario indicated that, to minimize residual storage, N should be applied according to plant needs, by using a real-time indicator based upon foliar analysis or the chlorophyll meter measurements. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Olive orchards are a key component of agricultural systems of the Mediterranean basin, occupying around 9.5 Mha in 2010, with more than 5 Mha in the European Union (FAOSTAT, 2012). In southern Portugal olive trees have been cultivated in traditional non-intensive or low tree-density orchards (around 200 trees ha -1 ) with no irrigation. Recently, to take advantage of the European Commission decision 2000/406/CE that expands the Portuguese planting quota together with the new Alqueva Irrigation Project in the Alentejo region, drip irrigation has been established to intensive orchards characterized by a high tree-density (300–400 trees ha -1 ) and super intensive orchards characterized by a very high tree-density (400–1700 trees ha -1 ). The Alqueva Irrigation Project is centered on the Alqueva dam, the largest strategic water reserve ∗ Corresponding author. Tel.: +351 21 365 34 78. E-mail address: roscameira@isa.ulisboa.pt (M.R. Cameira). in Europe, with a catchment area of approximately 10 000 km 2 and irrigating 120 000 ha of land. The Regional Department of Agricul- ture has estimated a total area of 350 thousand hectares of olive groves for the country, of which close to 160 thousand hectares are irrigated, including 45 thousand hectares occupied by inten- sive olive groves (RGA2009, 2011). The super intensive olive groves occupy an area of 4000 ha. In Alentejo these groves are installed mainly in Luvisols which are very common soils in Mediterranean climates, representing 20% of the area (approximately 500 thou- sand hectares) (Azevedo and Cary, 1989). The replacement of traditional rain fed orchards by highly pro- ductive irrigated orchards has resulted in an increase in the use of water and nitrogen (N) fertilizers, possibly bringing environmen- tal problems associated with the water bodies and jeopardizing the sustainability of these new agro ecosystems. This matter has received increasing attention as part of the policy debate and the media. Thereby it is necessary to evaluate the overall environmen- tal impact of these new production systems and if necessary to define alternatives for their management specific to the semi-arid http://dx.doi.org/10.1016/j.agwat.2014.09.007 0378-3774/© 2014 Elsevier B.V. All rights reserved.