Alfalfa rapidly remediates excess inorganic nitrogen at a fertiliser spill site

ABSTRACT cost remediation techniques when these approaches fail and when inorganic N affects ground water quality. Us-By 1996, standard remediation techniques had significantly reduced ing agricultural cropping systems to remove the excessthe concentration of nitrate nitrogen (NO23 –N) in local ground water N (phytoremediation) could be a practical and cost-at the site of a 1989 anhydrous ammonia spill, but NO23 –N concentra-effective approach at many sites.tions in portions of the site still exceeded the public drinking water standard. Our objective was to determine whether local soil and Nitrogen content of crops is a function of dry matter ground water quality could be improved with alfalfa (Medicago sativa production and crude protein concentration. Many cool-L.). A 3-yr study was conducted in replicated plots (24 by 30 m) season perennial forage crops have a longer growing located hydrologically upgradient of the ground water under the spill season, greater dry matter production, higher water use, site. Three alfalfa entries [‘Agate’, Ineffective Agate (a non-N2–fixing higher protein concentrations, and deeper root systems elite germplasm similar to Agate), and MWNC-4 (an experimental than annual crops. As a result, these perennial forages germplasm)] were seeded in the spring of 1996. Corn (Zea mays L.) can remove more N from soil and water than annualor wheat (Triticum aestivum L.) was seeded adjacent to the alfalfa crops. If the NO23 supply is large, however, some cropseach year. Crops were irrigated with N-containing ground water t