Pasture responses to zinc on Waitohi silt loam

Zinc deficiency on Waitohi silt loam, apparently induced by heavy applications of lime, led to low pasture production and even death of perennial ryegrass. The deficiency was overcome by applying zinc sulphate as a foliar spray, but topdressing with sulphate of ammonia, which increased soil zinc availability by reducing the pH, also corrected the problem.