Sodium requirements for temperate pastures in New Zealand: a review

Sodium (Na) is not an essential plant nutrient for forage pasture species but is required for optimal animal health and production. The distribution of Na in New Zealand pastures and soils is reviewed and evidence discussed indicating that the incidence of Na deficiency in animals, particularly dairy cows, is likely to increase with time. Vulnerable regions within New Zealand are identified. The results from New Zealand trials confirm that animal production responses to Na supplementation or fertiliser Na are unlikely to occur if the pasture Na concentration is greater than 0.10%. Results from trials examining the effects of Na fertiliser on pasture production and chemical composition are also reviewed. On soils with adequate soil potassium, Na has no effect on pasture production and applications of 50-100 kg NaCl/ha are sufficient to increase pasture Na concentration above the critical level for animal production (0.10% dry matter (DM)), even on soils with low initial soil Na concentrations (MAF Quick Test (QT) <10, 0.20 cmole Na kg(-1)). Methods for correcting Na deficiency in animals are also reviewed.