Developing a sustainable groundwater management system by decreasing nitrogen inputs

Nitrogen leaching through agricultural production soils may be a problem in the irrigated Mesilla Valley of southern New Mexico. The greatest leaching source is assumed to result from large amounts of nitrogen fertilizer bein g applied to shallow rooted, high-value vegetable crops, (i.e., cabbage, ch ile, lettuce and onion). However, limited information is available pertaini ng to the extent and management of nitrogen leaching to ground water. We mu st know the amount of nitrogen leaching to the ground water and the irrigat ion system efficiency in order to improve the current management practices. Therefore, our objectives are to (1) demonstrate to farmers that using chl oride as a tracer they can determine the irrigation and nitrogen use effici ency of their management system, (2) this information can be used to increa se profitability by decreasing nitrogen inputs, and (3) to develop a case s tudy describing the factors that determine the adoption of this natural res ources innovation. A technique using chloride in the irrigation water as a tracer has been use d to monitor nitrogen loading below the root zone and irrigation efficiency . Although farmers have stated that this agricultural innovation may be use ful, none have used it to monitor their management systems. Five farmers ar e currently working with the Cooperative Extension Service on this demonstr ation project. Soil samples were collected from 20 diverse field sites at 1 5-cm increments from 120 to 180 cm. The samples were analyzed for nitrate-n itrogen, chloride concentrations, soil moisture and texture. The partnershi p formed between these farmers and Extension has increased communication, c ooperation, and networking and should strengthen our future production prog rams. In addition, this collaborative group will evaluate if this innovatio n can be used to monitor, adjust nitrogen inputs, and improve their managem ent systems before extending to other farmers.