Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/30/1999
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Inorganic N contamination of ground water and soil is an increasing problem in many areas of the USA. Many of these sites can be remediated relatively inexpensively by using this important plant nutrient to produce high yielding, high quality perennial forage crops. The resulting forage is removed from the field and fed to livestock to convert the plant protein into milk and meat, achieving both N removal from the site and efficient conversion of inorganic N to food protein. Adapted perennials use more water and absorb more inorganic N than annual crops, thereby reducing potential nitrate leaching losses and maximizing total N removal. Both ammonium-N and nitrate-N are absorbed by these crops, although very high concentrations of ammonium-N are toxic to roots. Recently, we used alfalfa to clean up the site of a derailment in North Dakota by passive uptake from the soil and by irrigating the crop with N-impacted ground water. Although alfalfa can fix N from the atmosphere and does not require much inorganic for optimum growth, it has a tremendous capacity to absorb inorganic N. In addition, we used a special purpose, non-fixing alfalfa at this site. During three cropping years, alfalfa removed about 870 lb N/acre (970 kg N/ha), whereas annual grain crops removed only 260 lb N/acre (290 kg N/ha). During the third year, corn and the non-fixing alfalfa had similar above- ground yields, but N removal in alfalfa forage was over twice that in corn silage (370 vs. 160 lb N/acre; 410 vs. 179 kg N/ha). We are now working with a rural water district in southwest Minnesota on preventing nitrate contamination of a public water supply by planting perennial forages in the wellhead protection area and are investigating a new method to remove nitrate from the shallow aquifer using phytofiltration.