Nitrate contamination and its relationship with flood irrigation management

Nitrate contamination is a significant unresolved environmental issue for agriculture in the 21st century, with longstanding challenges in its control and allocation to a specified territory. In order to address these challenges, real-world meticulous irrigation area studies are required. The objective of this investigation is to analyze the evolution of nitrate contamination in relation to agronomic and management changes within a traditionally irrigated land. Specifically, the impact of changes in irrigation allowance assignment, changes in irrigation method from rotation to on-demand flood irrigation, and creation of water consumption accounts were analyzed. To this end, nitrogen monitoring and annual balances were carried out in a small irrigated hydrological basin (95 ha) located in Northeastern Spain throughout the years of 2001 and 2005-2008. The evolution of the nitrate contamination index was also analyzed, which relates the mass of nitrates exported to the fertilization necessities of a specific irrigated area. The results demonstrated that although changes in crop pattern caused a 33% reduction in the nitrogen required through fertilization, the fertilization rates applied are still double the necessities. Changes in irrigation management decreased the mass of nitrates exported by half and the nitrate contamination index by 24%, but the nitrate levels present are still approximately double of those registered in modern irrigation areas. The changes implemented by the Irrigation District in the irrigation management were effective. However, this study confirms that a greater effort is still required to achieve adequate nitrogen fertilization matching the crop necessities. (C) 2012 Elsevier B.V. All rights reserved.