SODIUM FERTILIZER APPLICATION TO PASTURE - 6 - EFFECTS OF COMBINED APPLICATIONS WITH SULFUR ON HERBAGE PRODUCTION AND CHEMICAL-COMPOSITION IN THE SEASON OF APPLICATION

The effect of sulphur and sodium fertilizers on the response of a pere nnial ryegrass (Lolium perenne) sward was examined over 2 years. Sulph ur fertilizer was applied as ammonium sulphate at 0 or 97.5 kg S ha(-1 ) year(-1) and sodium fertilizer as sodium nitrate at 0 (nil), 31 (low ), 62 (medium) or 94 (high) kg Na ha(-1) year(-1), with nitrogen input balanced across all treatments. Both sulphur and sodium increased her bage yield. Sodium fertilizer increased herbage sulphur concentration and sulphur fertilizer slightly increased herbage sodium concentration , but there were no major interactions between the two fertilizers on herbage yield or composition in the season of application. Sodium fert ilizer increased dry-matter digestibility, water-soluble carbohydrate concentration and the live proportion of the herbage. Herbage sodium a nd magnesium concentrations were increased and potassium concentration decreased by sodium fertilizer. Sulphur fertilizer increased herbage dry-matter digestibility and water-soluble carbohydrate concentration. Sulphur and potassium concentrations were also increased and non-prot ein nitrogen, magnesium and phosphorus concentrations decreased in res ponse to sulphur fertilizer. It is concluded that, although there was evidence of facilitation of sodium uptake by sulphur fertilizer and vi ce versa, this was not sufficient to produce synergistic effects on he rbage growth in the season of application.