Cover Crops for Saline Soils

Abstract

A 3-year study was conducted in the Central Valley of California to evaluate 125 prospective winter-growing cover crops for growth and nitrogen productivity in saline soils. Soil saturation paste electrical conductivities (ECes) in the surface 15 cm averaged 7dS m -1 at fall planting and 5.3 dS m -1 at spring harvest dates of each experiment. Species evaluated varied substantially in plant height. In general, the tallest plants were the Brassica species, which consistently grew to over 1.4m. Annual grasses (barley, rye, triticale and wheat) averaged about 1.0-1.3 m in each year. Of the legume species screened, heights were greatest for Hedysarum coronarium, Trifolium alexandrium, Vicia spp., and Medicago polymorpha and truncatula, averaging 59, 47, 39, 38 and 37 cm, respectively, over all experiments. About one third of the species screened produced crop cover in excess of 90% in each year. Groups of plants with consistently high crop cover percentages included various species/accessions of Brassica, Hedysarum, annual grasses, cool-season annual medics, Medicago polymorpha and Medicago truncatula, and two annual clovers, Trifolium alexandrium cv 'Multicut' and rose clover, Trifolium hirtum cv 'Hykon.' Total above-ground plant dry weights were highest for Brassica spp., which produced twice as much biomass as the annual grass species, and roughly four times as much dry matter as any of the legume species. Hedysarum, Lana and Namoi woolypod vetch, purple vetch, berseem clover, and several of the annual medic species consistently had the highest biomass among the legumes.