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A dynamic analysis of the tradeoffs between nitrate pollution of groundwater and economic returns to irrigated agriculture

Saeed Ahmad, University of Nebraska - Lincoln


Serious groundwater problems exist in Central Nebraska. Due to excessive irrigation and high use of nitrogenous fertilizer, in many areas the nitrate-N concentration in groundwater is two to three times the maximum contamination level of 10 ppm set by the EPA. ^ Using an optimal control approach that integrates hydrology and economics, a dynamic analysis was done to determine which water quality goals were achievable over the next 50 years and to find the least cost management practices. Base data on crop yields, water applied, nitrogen applied, and nitrogen leached was generated using the EPIC & APEX models. The crop activities considered included wheat, corn, soybeans and alfalfa under dryland and either gravity or sprinkler irrigation. ^ It was found that water quality could be improved over the next 50 years from 30 ppm to about 15 ppm at modest cost, but actions to reduce nitrate concentrations to levels below 15 ppm were likely to be prohibitively costly. The cost of improving water quality depended on the quality of the recharge water and on the size of the environmental goal. If the quality of the recharge water was 10 ppm, a mid range value, the incremental cost of water quality improvement ranged from about $3.50 per ppm per acre for the first five units of improvement to over $100 per ppm per acre to improve from 15 ppm to the best achievable level of 9 ppm. ^ For all water quality cases considered, the first option for improving water quality was always to reduce the amount of nitrogen applied to corn to about 95 percent of the profit maximizing level. If more water quality was desired the next best option was usually to go to as much sprinkler irrigated alfalfa as practical. Another management practice that was desirable under some circumstances was over irrigation of corn to minimize applied nitrogen while maximizing the amount of nitrogen supplied by irrigation water. ^

Subject Area

Hydrology|Economics, Agricultural

Recommended Citation

Ahmad, Saeed, "A dynamic analysis of the tradeoffs between nitrate pollution of groundwater and economic returns to irrigated agriculture" (2001). ETD collection for University of Nebraska - Lincoln. AAI3038971.