Legume seeding trials in a forested area of north-central Washington.
1995
Java B. | O'Dell T. | Lambert S.
Seeding nitrogen-fixing species is a proven silviculturnl practice to increase site nutrient capital, but species' responses are site specific. Alsike closer (Trifolium hybridum L.), white clover (T. repens L.), black medic (Medicago lupulina L.), cicer milkvetch (Astragalus cicer L.), two varieties of birdsfoot trefoil (Lotus corniculatus L.), and Hederma pine lupine (Lupinus albicaulis Dougl.) were planted at several elevations on the Wenatchee National Forest in Washington state. After 2 years, alsike clover and Hederma pine lupine were the most successful species on high-elevation (>1,219-m or 4,000-ft) sites, and black medic and Hederma pine lupine were the best performers on low-elevation sites. Average total nitrogen inputs from top growth of planted species during the 1991 growing season were between 20 and 115 kg/ha (18 and 103 lb/acre). Nitrogen delivered by atmospheric fixation was between 6 and 40 kg/ha (5 and 36 lb/acre). Legumes can successfully establish in eastern Washington, ameliorating losses in nutrients after logging and residue treatment. Legumes increased total nitrogen on these sites and enhanced nutrient cycling in planted areas.
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