Magnesium deficiency in pasture is almost unknown. On the other hand recent experimental work has shown that losses of magnesium from the topsoil may occur under urine spots and following topdressing with potassic fertilisers. With the widespread use of serpentine superphosphate and aerial superphosphate, appreciable quantities of magnesium are added to soils. It is possible therefore that these fertilisers are preventing the occurrence of magnesium deficiencies. Apple trees and possibly a few other crops of lesser importance are more sensitive to a low supply of available magnesium than pastures.
Co-creator
Cornelius During, B.AGR.SC., formerly Farm Advisory Service, Department of Agriculture, Wellington.