Sodium and potassium content of topdressed pastures in New Zealand in relation to plant and animal nutrition

Abstract

An extensive geographical survey was carried out to obtain information on the sodium and potassium content of topdressed grass-clover pastures in New Zealand. Results indicate that in many areas, especially away from the influence of sea spray, herbage sodium levels are below those estimated to be required by grazing animals. The associated potassium contents of these pastures, particularly in the North Island, are well in excess of animal needs and generally are more than adequate for plant nutrition. The possible effects on animal health of a low dietary intake of sodium coupled with excessive amounts of potassium are discussed. The importance of sources other than the plant in supplying sodium for animal needs is also pointed out. It is emphasised that there is an urgent need to assess fertiliser policy more in terms of the requirements of both plants and animals, by a plant analysis and balance sheet approach.