|Turyk, N - UNIVERSITY OF WISCONSIN|
|Shaw, B - UNIVERSITY OF WISCONSIN|
|Pearson, W - UNIVERSITY OF WISCONSIN|
Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 11, 2004
Publication Date: October 1, 2004
Citation: Russelle, M.P., Turyk, N.B., Shaw, B.H., Lamb, J.F., Pearson, W. 2004. Nitrogen and phosphorus uptake by alfalfa and leaching to ground water under an abandoned feedlot [abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts. CD-ROM. Paper No. 3408. Technical Abstract: Perennial forages may offer an effective, low cost method for remediating abandoned outdoor feedlot sites, and earlier research found that non-N-fixing alfalfa (Medicago sativa L.) may be more beneficial for cleanup than standard alfalfa. Duplicate plots (30 by 60 m) of N-fixing and non-N-fixing alfalfa were seeded at an abandoned feedlot on a Richford sandy loam in Portage County, WI, in August 1998; one replicate required reseeding in August 1999. The facultative nature of N fixation was evident, with less fixation occurring when alfalfa absorbed soil and manure N, but with uniform dry mass and total N yield across the site. Non-N-fixing alfalfa removed the same or less N from the soil and manure than N-fixing alfalfa, due largely to stand decline where inorganic N supply was inadequate for persistence of the non-N-fixing type. Maximum recovery of soil and manure N was about 450 kg N/ha over 3 yr for plots seeded with N-fixing alfalfa in 1998, and less where seeding was delayed. Despite this N removal, ground water nitrate concentrations increased by 50 to 80 kg nitrate-N/ha within 1 year after abandonment. Ground water P concentration did not change, but P apparently leached to 60- to 90-cm. We suggest that nitrate leaching losses after feedlot abandonment on coarse-textured soils may be minimized by seeding N-fixing alfalfa with a fast-growing companion crop, using no-till seeding to avoid soil mixing and aeration.