MINERAL FERTILISERS

Hawke's Bay Tribune, Volume XVII, 3 December 1927, Page 12

MINERAL FERTILISERS

HOW THEIB USE ORIGINATED.

Up to the middle of last century farmyard manure was the main source by which tho land was kept fertile, apart from liming, the value of which was recognised. It was thought by farmers, as well as by the majority of scientific men, that the fertilising excellence of farmyard manure c«usisted solely in its contents of organic matter supplying nitrogen, no consideration being given to its mineral elements, phosphate, and potash, etc. Liebig was the first man who emphasised in bis teaching the great importance of the minerals in the manure. This was in 1849, when he, in the course of lectures in England, promulgated the theory of the mineral nutrition of crops in opposition to the previously accepted view of the supreme importance of organic matter. He asserted that "it is exclusively inorganic elements which supply to plants their nourishment. ’ ’ This statement was received at the time with a good deal of scepticism, but the basis of its truth was demonstrated by the fact that plants were grown experimentally in soil deprived of organic matter but supplied with mineral eonsituents. Liebig argued that plants could get their requisite supply of nitrogen from the air, and that therefore tho essential part of manure was of furnish the minerals. Lawes combated that view, and proved by a series of experiments that the application of nitrogen was also necessary as crops with a few exceptions, could not utilise atmospheric nitrogen. Ho showed that the theory propounded by Liebig was exaggerated, although he agreed that it represented a great advance in agricultural knowledge and, acting on this knowledge, Lawes was' led to establish his factory on the Thames for the manufacture of superphosphate, and thus lay the foundation for the fertiliser industry as it exists to-day. It is now universally recognised (writes the Leader) that the return to the soil of the mineral constituents extracted by the crops is indispensable. By a for unate coincidence, just at the time when the restitution of the mineral elements was recognised and was becoming urgent, geological discoveries and the investigations of chemists revealed the existence in different parts of the world of enormous deposits of mineral phosphates and potash salts while more recently the recognised value of basic slag has placed another large source of phosphate at the disposal of farmers. Still more recently the wonderful process of the fixation of atmospheric nitrogen has assured a permanent supply of nitrogen, so that one is able to say that there is no anxiety for tho future as regards supplies of the three most important plant foods—nitrogen, phosphate, and potash.