Success of establishing nitrogen-fixing native species as cover crops in silt loam and loamy fine sand in a vineyard in the Columbia Basin

Abstract

Purshia tridentata (Pursh) DC. (antelope bitterbrush [Rosaceae]) and Psoralidium lanceolatum (Pursh) Rydb. (lemon scurfpea [Fabaceae]) were more likely to survive and increase stem numbers than were herbaceous native perennials in a test to establish native nitrogen-fixing cover crops in a vineyard in the Columbia Basin. Tests were done in silt loam and loamy fine sand fields. All seeds were locally collected. Plants were propagated in a greenhouse in 164 ml (10 in³) Ray Leach Cone-tainer cells. Plants were installed by hand. After 4 y, P. tridentata survival was 53%, independent of soil type. Stems of P. lanceolatum, a rhizomatous species, were 55% of the original number and expanding in the loamy fine sand field. Survival of Astragalus sclerocarpus A. Gray (woodypod milkvetch [Fabaceae]) appeared to stabilize at 25% and A. caricinus (M.E. Jones) Barneby (buckwheat milkvetch) at 20%, both in the silt loam field. Astragalus succumbens Douglas ex Hook. (Columbia milkvetch) and Lupinus leucophyllus Douglas ex Lindl. (velvet lupine [Fabaceae]) failed. Percentage of plants in flower for the herbaceous species decreased by the 4th y while the percentage of plants in flower increased for P. tridentata and stems of P. lanceolatum. Astragalus sclerocarpus and A. succumbens survival was significantly reduced because of increasing interference from the vegetative cover of grasses in the loamy fine sand field. Plants without flowers were significantly smaller than were plants that had flowered. Fifty percent of the herbaceous species experienced herbivory in 2011. There was no herbivory in P. tridentata or P. lanceolatum.