Submitted to: Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2011
Publication Date: 12/1/2011
Publication URL: http://handle.nal.usda.gov/10113/54024
Citation: TerAvest, D., Smith, J.L., Carpenter-Boggs, L.A., Granatstein, D.M., Hoagland, L.A., Reganold, J.P. 2011. Soil carbon pools, nitrogen supply, and tree performance under several groundcovers and compost rates in a newly planted apple orchard. Horticultural Science. 46(12):1687–1694. Interpretive Summary: Organic agriculture is expanding by 10 to 15% per year in the Pacific Northwest. Nitrogen is the most limiting plant nutrient especially in organic apple production. In addition, organic sources are often more expensive and release nitrogen slowly, which can result in lower yields and low leaf and fruit tissue nitrogen levels. Improving organic fertilizer-use efficiency with different amendments is critical to increasing cost efficiency in organic apple production. Brassica seed meal increased soil nitrogen supply, and earthworm activity but not total soil carbon and nitrogen or tree performance. Legume and non-legume cover crops reduced tree growth and yield compared to other treatments, regardless of compost rate. Wood chip mulch offered the best balance of production and soil quality of all treatments. This information is useful to producers as it provides information on alternative amendments for young apple orchards.
Technical Abstract: Organic mulches and cover crops add organic C and nutrients to soil, potentially affecting soil C and N pools and crop performance. This study evaluated the effects of in-row ground cover treatment (bare ground, brassica seed meal, cultivation, wood chip mulch, and legume and non-legume cover crops), and compost rate on soil C pools, biological activity, N supply, and tree performance in a young apple (Malus domestica Borkh.) orchard. Bare ground and cultivation treatments had large active soil C pools, 1.07 and 0.89 g kg-1 soil, respectively, but showed little stabilization of C into the slow soil C pool. Brassica seed meal increased soil N supply, slow soil C pool, and earthworm activity but not total soil C and N or tree performance. Legume and non-legume cover crops reduced tree growth and yield compared to other treatments, regardless of compost rate. Wood chip mulch mineralized the most C and had a high C:N ratio, resulting in N immobilization; but elevated earthworm activity, total soil C and N, slow soil C pool, and tree performance. Wood chip mulch offered the best balance of production and soil quality of all treatments.