. Elementary principles of agriculture; a text book for the common schools. Agriculture. Relation of the Plant to the Soil 79 rine, calcium, and magnesium. Tlie substances named occur in nearly all soils in quantities sufficient to supply the plants abundantly. Other substances, as potassium, phosphorus and nitrogen, are more important, and must be supplied when necessary. (See table of fertilizing substances in feecl-stuffs in Appendix). 112. The Form in Which Plants Take Up Their Mineral Food. These '*elements" occur in the soil as compounds with other substances. The soil is composed m
. Elementary principles of agriculture; a text book for the common schools. Agriculture. Relation of the Plant to the Soil 79 rine, calcium, and magnesium. Tlie substances named occur in nearly all soils in quantities sufficient to supply the plants abundantly. Other substances, as potassium, phosphorus and nitrogen, are more important, and must be supplied when necessary. (See table of fertilizing substances in feecl-stuffs in Appendix). 112. The Form in Which Plants Take Up Their Mineral Food. These '*elements" occur in the soil as compounds with other substances. The soil is composed mostly of. Fig. 44. Pot cultures of alfalfa showing effect of adding different fertilizers. D9, nothing; DIO, nitrogen; Dll, potassium, and D12,-phosphorus. Pho- tograph from Oklahoma Agricultural and Mechanical College. insoluble compounds, which the plants cannot use. The particles are very slowly changed into soluble compounds, and in this form are absorbed by the plants. The amount or per cent of soluble matter in the soil water at any one time is exceedingly small, as shown by the analysis of natural waters. In fact, if the amount should exceed ten parts in a thousand the effect would be unfavorable on the growth of the plant. The total amount of, say, potash in the soil may be several per cent of the total soil weight, yet the amount in solution at any time may rarely exceed fifty parts per million of water. It is well. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ferguson, A. M. (Alexander McGowen), 1874-; Lewis, Lowery Laymon, 1869- joint author. Sherman, Tex. , Ferguson Publishing Company
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