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Irrigation management and pollution by salts and nitrate: Flood vs. pressurized system

Abstract:

Irrigated agriculture allows the increase of agrarian yields and the stability in food supply, but it is also considered the main fresh water consumer and polluter in the world. This work aims to evaluate water use and pollution of two irrigation lands (flood-and pressurized-irrigation) based on the analysis of irrigation efficiency, salt contamination index (ICS) and nitrate contamination index (ICN) for each irrigated land during the hydrological years 2006-2008. Irrigation efficiency was similar in both irrigation lands (84%), revealing the possibility of reaching adequate efficiencies with implementations in the irrigation systems. Regarding pollutants, the highest mass of salt exported was recorded in the irrigated land with most saline soils (Dsalt fllood = 1.7 t/ha-year vs. D salt.press = 3.2 t/hayear) and the highest mass of nitrate exported was detected in the irrigated land with lowest nitrogenous fertilizer supplies, but with highest volume of drainage (Qflood = 446 mm vs. Q press = 116 mm). Contamination indices showed better results for the pressurized-irrigation land (ICS = 1.6 t ha-1/ds m-1; ICN = 0.68), proving that it is possible to reduce the contamination of irrigated lands decreasing irrigation return flows.