Identification of nitrate leaching hot spots in a large area with contrasting soil texture and management

Identification of nitrate (NO3) leaching hot spots is important in mitigating environmental effect of NO3. 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 NO3 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 NO3-N concentrations demonstrated a considerably high variation, with a mean of 10.2 mg kg−1 and 2.1 mg L−1 NO3-N for soil and groundwater, respectively. The NO3-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 NO3 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 NO3 effect in these hot spot areas.

Research highlights
► Nitrate leaching often occurs in intensively cultivated agricultural areas.
► We studied nitrate leaching hot spats in a 36,000 ha plain in Southeastern Turkey.
► We detected six isolated nitrate leaching hot spots in the plain.
► Soil texture and irrigation occurred as the major factors of nitrate leaching.
► Alternative crop, water, and soil management practices needed adapting in these hot spots.