The effect of salinity level upon the yield, root growth, and water extraction of contrasting rooting subpopulations of alfalfa (Medicago sativa) under conditions of zero leaching

A major problem in irrigated agriculture in the Western U.S. is the gradual accumulation of salinity in the plant root zone. These nonuniformly saline soils contain increasing amounts of salinity with depth, and salt accumulation is accelerated in situations where leaching is minimized. Root growth is limited in these soils and thus plant yield is reduced due to decreased water uptake. We studied the root growth of two subpopulations of alfalfa differing in their ability to produce fibrous roots to determine if altering root morphology would increase water extraction and plant yield in an irrigated saline soil.;Soil profiles for a control and three treatments with increasing salinity were packed into PVC cylinders fitted with a flat window down one side for root measurements. A single alfalfa plant was grown from seed in each cylinder and irrigated with water enriched primarily in sulfate-dominated salts. Alfalfa plants were grown for five successive harvests in a greenhouse, and water extraction was measured in the control and high salinity treatment by time-domain reflectometry. Final electrical conductivities of soil ranged from 3.0 to 23 dS m...