Loss Of Plant-food

Categories: THE NEED OF COMMERCIAL FERTILIZERS

The soil is composed chiefly of material that

never will enter into the structure of plants, but that serves us by

affording a congenial place for plant-roots. It anchors the plants,

holds moisture for them, and offers opportunity for all the processes

necessary to the preparation of plant-food and to its use. In this

material are the abundant supplies of such plant-food as silica, but,

as has been previously stated, t eir very abundance leads us rightly to

disregard them in our thinking. Our interest is only in the very small

percentage of material that is composed of the four constituents which

may be lacking in available form in the soil: nitrogen, phosphoric

acid, potash, and lime. We believe that the only consideration that now

need be given lime is as a soil-corrective and, when there is no

acidity, we may assume that there is plenty of lime present. When

yields of crops tend to decrease, the only plant-foods with which we

are concerned are nitrogen, phosphoric acid, and potash.



The materials were stored in all agricultural land, and much of the

supply is in inert forms. They help to make what we call the natural

strength of the land. The rotting of organic matter, tillage, and many

other agencies bring about some availability. The removal of crops,

leaching, etc., reduce the supply. The right use of commercial

fertilizers involves the addition of some plant-food when the available

supply in a particular soil is inadequate.