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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Applied Engineering in Agriculture. 17(5): 601–610. (doi: 10.13031/2013.6919) @2001
Authors:   M. S. Al–Jamal, T. W. Sammis, S. T. Ball
Keywords:   Chloride, Best management practices, Irrigation efficiency, Nitrate–nitrogen

Groundwater contamination caused by nitratenitrogen (NO3 N) leaching through soils is becoming a serious problem in the irrigated Mesilla Valley of southern New Mexico. The greatest groundwater contamination probably results from large amounts of nitrogen fertilizer being applied to shallowrooted, highvalue vegetable crops (i.e., onion, lettuce, and chile). The main objective of the study was to demonstrate to farmers that a chloride tracer could be used to determine the irrigation and nitrogenuse efficiency of their management system and how decreasing nitrogen (N) inputs will affect profitability.

Five farmers (representing 60% of the farmers that are the technology diffusion leaders in the county) were chosen as innovative farmers who would transfer the technology to others. The average estimated irrigation efficiencies obtained from the farmers fields were high, ranging from 87 to 97%. These unexpectedly high irrigation efficiencies under furrow irrigation were a result of the farmers practicing deficit irrigation due to limited water resources. However, deficit irrigation resulted in yields below maximum yield (considered to be near the average county yield). The amount of NO3 N leached ranged from 9 kg/ha under fall lettuce to 152 kg/ha under chile. The 152 kg/ha obtained from the chile fields had a calculated average N application efficiency of 57%, resulting in an average NO3 N concentration greater than the maximum contamination level allowed for drinking water of 10 mg/L.

Although the NO3 N leached below farmers fields was high, the farmers did not think it was their responsibility to change management practices unless their profits would increase. Farmers rejected the adoption of the technology because they felt the costs outweighed the benefits. Consequently, transfer of this technology to the farmers failed. The farmers indicated that they would adopt the technology only if forced to by a regulatory agency.

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