Elementary principles of agriculture : a text book for the common schools elementaryprinci02ferg Year: 1913 Relation of the Plant to the Soil 79 available soil and add the substances to the soil. This is called fertilizing the soil. Fig. 43 illustrates the effect of applying different fertilizing substances to a sandy soil taken from a field in Eastern Texas. Fig. 44 shows the effect of adding nitrogen, potassium and phosphorus to pot-cultures of alfalfa made at the Oklahoma Agri- cultural and Mechanical College. Fig. 43. Effect of fertilizers on fine sandy loam. An application of phos- p
Elementary principles of agriculture : a text book for the common schools elementaryprinci02ferg Year: 1913 Relation of the Plant to the Soil 79 available soil and add the substances to the soil. This is called fertilizing the soil. Fig. 43 illustrates the effect of applying different fertilizing substances to a sandy soil taken from a field in Eastern Texas. Fig. 44 shows the effect of adding nitrogen, potassium and phosphorus to pot-cultures of alfalfa made at the Oklahoma Agri- cultural and Mechanical College. Fig. 43. Effect of fertilizers on fine sandy loam. An application of phos- phoric acid is denoted by P; potash by K; nitrogen by N. 111. The Quantity of Fertilizing Substances added to the soil is but a small fraction of the increased weight of the crop which it produces. Minerals are absorbed by the plants in exceedingly small amounts, for they form only about one part in two hundred of the fresh, living plant, and rarely more than five per cent of the dry substance. They are necessary as food substance; they become a part of the living plant substance. Exceedingly small amounts suffice in the case of iron, sulphur, chlo-
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