Legume Cover in Orchard Drive Alleys

David  Granatstein; Pamela Pavek

doi:10.7273/000002511

Orchardists in Washington State are interested in finding an alternative source of nitrogen to offset the need for commercial fertilizer, which can be expensive, difficult to transport and apply, and may cause reductions in soil pH and fruit quality. Previous studies suggest legumes grown as drive alley cover may be able to supply up to 50% of the nitrogen requirements of an orchard, however a more extensive evaluation of legume species and varieties was necessary. An assessment of 25 different legumes was conducted in three apple orchards in the Yakima River Valley in south-central Washington. Legumes were planted in 100 ft long plots in drive alleys at each site and evaluated two to four times per year for three years. Measurements taken include percent establishment, percent cover, plant height, percent biomass nitrogen, and biomass and nitrogen production. An economic analysis was also conducted to determine the value of the nitrogen contribution in both organic and conventional orchards. Alfalfa varieties had higher percent cover (50 to 100%), more biomass (2,500 to 4,500 DM lb/ac/yr) and biomass nitrogen production (80 to 180 lb N/ac/yr) than the clover and other legume species. Alfalfa biomass nitrogen was significantly higher than clover biomass nitrogen in three out of four site x year combinations. Economic analysis showed after three years of production in an organic orchard, the alfalfa varieties, some white clover varieties, and 'Dominion' red clover had the potential to compensate for their establishment costs with the value of nitrogen they produced. Some alfalfa varieties also compensated for establishment costs in a conventional orchard. INTRODUCTION Organic and conventional orchardists in Washington rely on external sources of nitrogen, which can be expensive, labor intensive and sometimes result in lower soil pH or increased salinity and reduced fruit quality (Stamatiadis et al., 1999; Hoagland et al., 2008). Legumes grown in orchard drive alleys may provide a more sustainable, less expensive, on-farm source of nitrogen. In a previous study, a 4 foot wide legume strip in the drive alley was able to supply approximately 50% of the nitrogen required by the orchard, and increased levels of plant-available nitrogen were detected in the tree row following " mow and blow " management (Davenport and Granatstein, 2010). Four legumes were evaluated in that study; they include: kura clover (Trifolium ambiguum M. Bieb), 'Ladino' white clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.), and alfalfa (Medicago sativa L.). A more extensive screening of legumes was needed to determine the ideal species and cultivars that have the potential to supply nitrogen. The objective of this trial was to evaluate a broad spectrum of legume species and cultivars for their ability to thrive in an orchard environment and provide a significant nitrogen contribution.

Legume Cover in Orchard Drive Alleys

Files and links (1)

Abstract

Metrics

Details