Salinity effects on forage quality of Russian thistle.

Abstract

Russian thistle (Salsola iberica Sennen and Pau), a common weed found on overgrazed rangelands, abandoned farmlands, and other disturbed sites in the western United States, is often grazed by livestock and in times of drought has been extensively harvested for hay. Much of the land where Russian thistle grows in the western United States has a salinity hazard. The purpose of this study was to determine the effects of salinity stress on forage quality of Russian thistle. Russian thistle plants were grown in a greenhouse in sand culture irrigated with salinized nutrient solutions (electrical conductivities of 1.3, 10.6, 19.5, 26.8, and 33.9 dS/m) prepared with NaCl and CaCl2 (2:1 molar ratio). Chemical indices of forage quality (total N, neutral detergent fiber, acid detergent fiber, acid detergent lignin, nitrate, and oxalates) at 2 growth stages (early flower and full flower) were determined. Forage quality of Russian thistle, as measured by total N and fiber constituents, improved with increasing salinity. Mineral ash content increased with salinity stress at both growth stages but was reduced slightly by increasing maturity. Nitrate levels increased at early flower but decreased at full flower with increasing salinity, whereas oxalate-levels at both growth stages were reduced by salinity. Neither component was of sufficient magnitude to be toxic to ruminants. These results indicate that salinity stress is not detrimental to forage quality of Russian thistle but tends to improve it.