Irrigation management, nitrogen fertilization and nitrogen losses in the return flows of La Violada irrigation district (Spain)
2012
Barros, R. | Isidoro, D. | Aragües, R.
Nitrogen (N) pollution induced by irrigated agriculture is a significant environmental problem. The main N inputs and outputs were measured or estimated in the semi-arid La Violada irrigation district (Spain). Data on two periods (1995–1998 and 2006–2008) were compared and related to observed changes during the decade in cropping patterns and N fertilization and irrigation management. N fertilization exceeded crop N uptake due to over-fertilization of corn (426kgN/ha in 1995–1998 and 332kgN/ha in 2006–2008) and alfalfa (62kgN/ha). Between the two periods, N fertilization decreased by 56%, primarily due to a change from corn to alfalfa and barley. Accordingly, N losses in the irrigation return flows (IRF) diminished from 31% of the applied fertilizer in 1995–1998 to 20% in 2006–2008. NO₃ ⁻ concentrations and NO₃-N loads in the IRF decreased from 40mg/L and 106kgN/ha in 1995–1998 to 21mg/L and 22kgN/ha in 2006–2008, due to lower N fertilization, lower corn area and improved irrigation efficiency. N contamination in the IRF will be minimized by increasing the irrigation efficiency and decreasing the corn area and its N fertilization rates, particularly when supplemental organic N is applied at pre-sowing.
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