I am half tempted to omit entirely any discussion of chemical
fertilizers: to give a list of them, tell how to apply them, and let
the why and wherefore go. It is, however, such an important subject,
and the home gardener will so
frequently have to rely almost entirely upon their use, that probably it will be best to explain the subject as thoroughly as I can do it in very limited space. I shall try to give the theory of scientific chemical manuring in one paragraph. We have already seen that the soil contains within itself some available plant food. We can determine by chemical analysis the exact amounts of the various plant foods--nitrogen, phosphoric acid, potash, etc.--which a crop of any vegetable will remove from the soil. The idea in scientific chemical manuring is to add to the available plant foods already in the soil just enough more to make the resulting amounts equal to the quantities of the various elements used by the crop grown. In other words: ) Available plant food elements in ( the soil, plus > == Amounts of food elements Available chemical food elements ( in matured crop supplied in fertilizers ) That was the theory--a very pretty and profound one! The discoverers of it imagined that all agriculture would be revolutionized; all farm and garden practice reduced to an exact science; all older theories of husbandry and tillage thrown by the heels together upon the scrap heap of outworn things. Science was to solve at one fell swoop all the age- old problems of agriculture. And the whole thing was all right in every way but one--it didn't work. The unwelcome and obdurate fact remained that a certain number of pounds of nitrogen, phosphoric acid and potash--about thirty-three--in a ton of good manure would grow bigger crops than would the same number of pounds of the same elements in a bag of chemical fertilizer. Nevertheless this theory, while it failed as the basis of an exact agricultural science, has been developed into an invaluable guide for using all manures, and especially concentrated chemical manures. And the above facts, if I have presented them clearly, will assist the home gardener in solving the fertilizer problems which he is sure to encounter.
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