Effects of sodium fertilizer, cultivar, temperature and growth stage on the mineral content and nutritive value of sorghum forage

Abstract

The effects of sodium application, growth stage and temperature on the mineral content and nutritive value of four forage sorghum cultivars are reported. The forages were grown in pots in glasshouses maintained at day/night temperatures of 23/16°C and 32/25°C with a 14 h photoperiod. The application of sodium chloride (equivalent to 41 kg Na/ha) increased the sodium content of plant tops from 0.014 to 0 018% but even the enhanced value is well below the minimum recommended for animal production. Sodium application also decreased the sulfur content of the forage and widened the nitrogen to sulfur ratio. Increased temperature reduced the in vitro digestibility, particularly of stem tissue (2.11 percentage units/°C). Age had a marked effect on the in vitro digestibility of the forage, which decreased by 0.3 percentage units/d.