A major break through in plant nutrition work occurred in 1958, when G. M. Will, of the Forest Research Institute, Whakarewarewa, Rotorua, clearly showed that the yellow stunted growth in seedling trees could be quickly corrected by the application of magnesium. This showed that the nursery soil was deficient in magnesium for tree growth; the burning question was, is this soil so deficient in available magnesium that a response will be obtained from an application to pasture plants? The answer was a definite yes, and for the first time we had a pasture trial giving significant responses to applied magnesium.