Nitrogen Fertilization of Irrigated Russian‐Thistle Forage. I. Yield and Water Use Efficiency1

Abstract

AbstractReports on yield, water use efficiency, and nutritive value of Russian‐thistle (Salsola spp.) have suggested its potential as a forage crop for areas with limited water resources. This study was initiated to determine the effect of N fertilization, irrigation management, time of first harvest, and cutting height on the yield and water use efficiency of Russian thistle. Russian‐thistle was grown in irrigated field plots in 1975 and 1976. The influence of N fertilization (0, 28, 56, 112, and 224 kg N/ha), stage of maturity at first harvest (prebloom and 3/4 bloom), and cutting height (7.5 and 15.0 cm) on dry matter yield and water use efficiency was evaluated in 1975. Yield and water use efficiency generally improved as N application rates increased. Thistle harvested at 3/4 bloom produced 3,600 kg/ha more dry matter and 27% more shoot dry weight/ha‐cm of water applied than thistle cut at prebloom. Cutting at 15 cm increased yield by 8 and 15% at prebloom and 3/4 bloom, respectively, over that at 7.5 cm. In 1976, application of N (0, 28, 56, and 112 kg N/ha) generally improved both yield and water use efficiency. Quantity of water applied (24, 35, 40, and 60 cm) did not significantly affect yield but the highest application reduced water use efficiency. No N fertilizer ✕ irrigation interactions occurred. Forage yields ranged from 6,090 to 11,009 kg/ha and water use efficiency from 102 to 414 kg shoot dry weight/ha‐cm of water applied.