I cannot claim any originality in the title of this paper, since during the past hundred years dozens of papers have been written under the identical heading and hundreds -have been written on the same topic. In the hour that is allotted to me I propose to discuss, not the mineral status of pastures grown under all the environmental conditions possible in New Zealand, but one or two small trials which have been under ";~-v; in Palmerston North during the past 3 years. reason for this intense specialisation will, I hope, become clear as the lecture proceeds, but briefly we are concerned with principles which will be applicable regardless of the environmental conditions rather than with applications which relate only to one particular climate or one particular soil.
