. Botany, with agricultural applications. Botany. WATER, AIR, AND HUMUS OP THE SOIL 153 and air which the roots and micro-organisms of the soil must have. Although not tightly packed, the -particles adhere to each other when moist, and this feature and the weight of the soil enable roots to obtain a firm Fig. 136. â Diagram of two root hairs and the soil around them. The soil particles are shaded and the light area around each soil particle repre- sents a film of water. The large light areas among the soil particles are air Modified from J. G. Coulter. Water, Air, and Humus of the
. Botany, with agricultural applications. Botany. WATER, AIR, AND HUMUS OP THE SOIL 153 and air which the roots and micro-organisms of the soil must have. Although not tightly packed, the -particles adhere to each other when moist, and this feature and the weight of the soil enable roots to obtain a firm Fig. 136. â Diagram of two root hairs and the soil around them. The soil particles are shaded and the light area around each soil particle repre- sents a film of water. The large light areas among the soil particles are air Modified from J. G. Coulter. Water, Air, and Humus of the Soil. â To the plant the water of the soil has two important functions. First, it is the reservoir upon which the plant depends for water. Second, water is the solvent in which the soil substances become dissolved before â entering the plant. The amount of soil water varies for different kinds of soils, and for the same soil at different times. Thus garden soil rich in humus or a very heavy clay soil will hold two or three times as much water as a sandy soil. Just after a heavy rain soils are ⢠⢠saturated with water, that is, all of the spaces are fiUed. But much of this water, known as free water, gradually sinks away toward the center of the earth in response to its own weight, leav- ing the pores partially empty. The water then remaining in the pores consists chiefly of capillary water, which is held in the pores by the force of capillarity. In addition to the capillary water, which does not respond to the influence of gravity, there is also the hygroscopic water, which remains, after the capillary water is removed, as a thin film around each particle and so firmly held. 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 Martin, John N. (John Nathan), b. 1875. New York, John Wiley & sons, inc.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1920
