Nitrogen Management Tools in an Irrigated Agricultural Land.

Nitrogen Management Tools in an Irrigated Agricultural Land H. Ibrikci1*, M. Cetin2, H. Sagir1, E. Karnez3, M. Fink4, M. Glavan5, M. Pintar5 and J. Ryan6 (1) Cukurova Univ., Soil Sci. and Plant Nutrition Dept. Adana, Turkey (2) Cukurova Univ., Agric. Structures and Irrigation Dept. Adana, Turkey (3) Cukurova Univ., Karaisali Vocational School, Karaisali, Turkey (4) Friedrich-Schiller-Univ., Geo-informatics, Hydrology and Modelling Dept. Jena, Germany (5) Department for Agronomy, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana (6) Consultant, Carrigataha, Cahir, County Tipperary, Ireland Nitrogen (N) fertilizers and irrigation are the main inputs of dry-area agricultural production. Nitrogen dynamics and cycling in such ecosystems are always complex, especially with irrigation water and precipitation. As nitrate (NO3) - N is very mobile in soil, it can easily be leached to water bodies resulting in related pollution risks on human health and environmental and agricultural systems. There are several approaches to improve N management and to quantify the level of NO3 loss in water resources at the catchment level, e.g., temporal and spatial NO3 monitoring to identify the level and load of NO3 in soil, plant and water, N-budget calculations, modeling and conceptual evaluation (e.g., DPSIR or driver-pressure-state-impact-responses) with potential to improve field practices. Therefore, these four tools were used in an irrigated sub-catchment (Akarsu, 9495ha) in a Mediterranean region of southern Turkey from 2009 to 2016. Soil, water and plant samples were periodically collected, analyzed, modelled and evaluated in irrigation and non-irrigation seasons as well as the hydrological year (October 1st to Sept. 30th of the following year). Based on the findings, up to 380 kg N ha-1 y-1 used as fertilizer for the major crops, such as corn. A total of 75 to 120 kg mineral N ha-1 y-1 accumulated in the rooting depth, while up to 60 kg N ha-1 y-1 was lost to drainage, mostly either in mid-winter or mid-summer depending on fertilization and irrigation practices. The SWAT model prediction of N loss closely confirmed the observed values. The long-term results indicate that N fertilizers and amount of irrigation water or precipitation received were the major inputs promoting N losses to drainage. These two parameters should be managed for environmentally sound crop production. Keywords: nitrogen management, nitrogen loss, drainage water