NATURE’S CYCLE

Southland Times, Issue 23989, 2 December 1939, Page 14

NATURE’S CYCLE

MINERAL SUPPLY IN SOIL SALE OF STOCK MEANS LOSS If Nature’s cycle of mineral circulation from soil, through plants to animals and back to soil again, was undisturbed, the mineral supply in the soil would be maintained. In practice, however, the natural mineral cycle is not completed. The sale of crops, live stock and milk from farms represents a loss of minerals from the soil which if not balanced by an equivalent return in some other forms, must eventually result in soil depletion. So far as soils and crop plants are concerned,

a variety of deficiencies is possible, depending on the original mineral content of the soil and the losses suffered during the time it has been under cultivation. What bearing some of these soil deficiencies may have on animal nutrition is not known, but their possible significance should not be overlooked. Phosphorus is one of the first, of the mineral nutrients to become deficient in cultivated soils. It is well understood that, in most soils, the total supply of phosphorus is considerably less than. that of nitrogen, potassium, calcium or magnesium, writes an English authority. DRAIN ON PHOSPHORUS Experiments have shown, states the same authority, that phosphorus is taken up in large amounts from the soil during the early growth of the plant. The maintenance of an adequate supply of phosphorus, in a readily available form, is thus a critical factor in the normal nutrition of the plant. If the available phosphorus supply is reduced to a level insufficient to meet the needs of a rapidly growing crop, phosphorous deficiency results, even though the total supply in the soil may be considerable. Loss of "available phosphorus from the soil by leaching is negligible. The serious losses result from crop removal. Depletion of soil, phosphorus results from failure to replace the losses, either directly or through the medium of the manure produced from feeding the crops to live stock. Under the best conditions of British live stock farming it is estimated that not more than three-quarters of the phosphorus in the feed and bedding is recovered in the manure.