SOIL FERTILITY

Wairarapa Times-Age, 14 June 1939, Page 3

SOIL FERTILITY

BALANCED FOOD NECESSARY. REPLACEMENT ASPECT. In many cases the word “fertiliser” means to the New Zealand farmer, superphosphate, and is looked upon as a universal plant food, irrespective of what has to be produced from, or replaced, in the soil. Superphosphate, under many conditions, is not be despised, but the main object in supplementing soil fertility should be to keep the available plant food properly balanced. Soil analysis is not a guide for fertilising. The analysis shows the total supply of plant food, but not the available amount. Soils thus respond to applications of a fertiliser, even though their chemical analysis shows a high total content of the same element. For instance, potash may be shown by soil analysis to be present in large quantities, but until it is made available by the application of lime it cannot be used as a plant food by the immediate crop. Well-balanced soil fertility cannot be achieved solely by the use of one fertiliser, superphosphate. All plant life requires at least the four essential elements, viz., phosphorous (phosphates), potassium (potash), nitrogen (nitrates), and calcium (lime). Cropping, milk production, rearing and feeding of livestock. all tend to reduce the supply of these elements in the soil, because the products are carried off the farm. A certain amount of these elements is returned to the soil through livestock manure, but in the case of a milking cow these droppings are not nearly so. valuable as are those from fattening stock, for valuable mineral properties are retained by the cow for milk production.

Therefore the farmer’s fertilising programme, to maintain soil fertility, should be such as will supply the elements lacking, or which will replace those depleted.