Agricultural Water Management 98 (2011) 1013–1019 Contents lists available at ScienceDirect Agricultural Water Management journal homepage: www.elsevier.com/locate/agwat Identification of nitrate leaching hot spots in a large area with contrasting soil texture and management A. Kurunc a , S. Ersahin b,∗ , B. Yetgin Uz c , N.K. Sonmez a , I. Uz c , H. Kaman a , G.E. Bacalan a , Y. Emekli a a Department of Agricultural Structures and Irrigation, Faculty of Agriculture, Akdeniz University, 07058 Antalya, Turkey b Department of Forest Engineering, Faculty of Forestry, C ¸ ankırı Karatekin University, 18100 C ¸ ankırı, Turkey c Department of Soil Science and Plant Nutrition, Faculty of Agriculture, Akdeniz University, 07058 Antalya, Turkey article info Article history: Received 19 September 2010 Accepted 15 January 2011 Available online 18 February 2011 Keywords: Geostatistics Groundwater nitrate Soil nitrate Spatial variation Irrigation abstract Identification of nitrate (NO 3 ) leaching hot spots is important in mitigating environmental effect of NO 3 . Once identified, the hot spots can be further analyzed in detail for evaluating appropriate alternative management techniques to reduce impact of nitrate on groundwater. This study was conducted to identify NO 3 leaching hot spots in an approximately 36,000 ha area in Serik plain, which is used intensively for agriculture in the Antalya region of Southern Turkey. Geo-referenced water samples were taken from 161 wells and from the representative soils around the wells during the period from late May to early June of 2009. The data were analyzed by classical statistics and geostatistics. Both soil and groundwater NO 3 -N concentrations demonstrated a considerably high variation, with a mean of 10.2 mg kg -1 and 2.1 mg L -1 NO 3 -N for soil and groundwater, respectively. The NO 3 -N concentrations ranged from 0.01 to 102.5 mg L -1 in well waters and from 1.89 to 106.4 mg kg -1 in soils. Nitrate leaching was spatially dependent in the study area. Six hot spots were identified in the plain, and in general, the hot spots coincided with high water table, high sand content, and irrigated wheat and cotton. The adverse effects of NO 3 can be mitigated by switching the surface and furrow irrigation methods to sprinkler irrigation, which results in a more efficient N and water use. Computer models such as NLEAP can be used to analyze alternative management practices together with soil, aquifer, and climate characteristics to determine a set of management alternatives to mitigate NO 3 effect in these hot spot areas. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Over-fertilization to obtain greater crop yield has triggered excessive nutrient loads in soil, groundwater, and surface water of agricultural regions (Volk et al., 2009; Kundu et al., 2009). Agri- cultural activities, involving the application of excessive inorganic nitrogen fertilizers, lead to groundwater pollution by nitrate (NO 3 ) leaching from agricultural lands. As NO 3 is a water soluble and negatively charged ion, under aerobic conditions, surplus NO 3 is readily transported by percolating water through the soil profile and accumulates in aquifers (EPA, 1987; van Duijvenboden and Loch, 1983). The fate of NO 3 -N in soil is affected by the position of a water table and an aquifer, rainfall and irrigation, organic matter content, and other chemical soil properties (van Duijvenboden and Loch, 1983). Water flow and NO 3 leaching from root zone to aquifer are also controlled by soil physical characteristics, such as soil hydraulic ∗ Corresponding author. Tel.: +90 376 213 2626; fax: +90 376 212 8118. E-mail address: ersahin@karatekin.edu.tr (S. Ersahin). conductivity, water holding capacity, texture, thickness, soil struc- ture, and characteristics of soil pores. In general, soil water moves downward more rapidly in sandy soils than in clayey soils, resulting in NO 3 movement to greater depths. Nitrate leaches less likely in soils with greater water holding capacity (Knox and Moody, 1991; Lægreid et al., 1999). High NO 3 -N in groundwater causes toxicity in human and animals. The EU and the World Health Organization considers 50 mg L -1 NO 3 (11.3 mg L -1 NO3-N) to be the critical value for drinking water (EC, 1998; WHO, 2006). The Environmental Pro- tection Agency of the USA set this value to 10 mg L -1 NO 3 -N (EPA, 2009). Nitrate levels exceeding 50 mg L -1 in drinking water may cause a disease known as methaemoglobinaemia with symptoms of cyanosis and asphyxia, especially in bottle-fed infants (WHO, 2007). Pollution of groundwater by nitrate leaching is a common prob- lem worldwide (Flipo et al., 2007; Anayah and Almasri, 2009). The WHO (2007) reported that the percentage of the population exposed to NO 3 levels above 50 mg L -1 in drinking water ranges from 0.5 to 10%, corresponding to nearly 10 million people in Europe. Hu et al. (2005) reported that groundwater pollution by 0378-3774/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2011.01.010