. The nature and properties of soils; a college text of edaphology. Soils. SOIL STRUCTURE AND ITS MODIFICATION 149 83. Soil tilth.—Tlie previous data and discussion have clearly shown the very great importance of structure in the successful handling of the soil in the field. Since good phy- sical condition will reflect itself on crop yield it is evident that structure must ultimately be considered in relation to all plant growth. This relationship is usually expressed by the term tilth, "While structure refers to the arrangement of the particles in general, and granulation to a particular
. The nature and properties of soils; a college text of edaphology. Soils. SOIL STRUCTURE AND ITS MODIFICATION 149 83. Soil tilth.—Tlie previous data and discussion have clearly shown the very great importance of structure in the successful handling of the soil in the field. Since good phy- sical condition will reflect itself on crop yield it is evident that structure must ultimately be considered in relation to all plant growth. This relationship is usually expressed by the term tilth, "While structure refers to the arrangement of the particles in general, and granulation to a particular aggre- gate condition, tilth goes one step farther and includes the plant. Tilth, then, refers to the physical condition of the soil. Fig. 27.—A planter or drag, useful in the crushing of clods. as related to crop growth. It may be poor, medium, good, or excellent, according to circumstances. Good tilth may de- mand in many soils maximum granulation, in others only a medium development. Tillage operations by influencing the structure of the soil aim to develop optimum tilth. Optimum tilth always implies the presence of water since the best phys- ical relationships cannot be developed without such moisture conditions. 84. SumGtnary.—The factors which control the struc- tural condition of the soil to the greatest extent are plasticity and cohesion, their influence intensity being due directly to the presence of certain kinds of materials, especially hydrated aluminum silicates, in a colloidal state. As plasticity and cohesion increase the tendencies of a soil to puddle when wet. 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 Lyon, T. L. (Thomas Lyttleton), 1869-1938; Buckman, Harry Oliver, 1883-. New York, Macmillan
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