Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER I PHYSICAL PROPERTIES OF SOILS 1. Soil.—Soil is disintegrated and pulverized rock mixed with animal and vegetable matter. The rock particles are of different kinds and sizes, and are in various stages of decomposition. If two soils are formed from the same kind of rock and differ only in the size of the particles, the difference is merely a physical one. If, however, one soil is formed largely from sandstone, while the other is formed from limestone, the difference is both physical and chemical. Hence it is that soils differ both physically and chemically. It is difficult to consider the physical properties of a soil without also considering the chemical properties. The chemical and physical properties, when jointly considered, determine largely the agricultural value of a soil. 2. Physical Properties Defined. — The physical properties of a soil are : 1. Weight, 2. Color. 3. Size, form, and arrangement of the soil particles. 4. The relation of the soil to water, heat, and cold. 5. Odor and taste. 6. The relation of the soil to electricity. 3. Weight.—Soils differ in weight according to the composition and size of the particles. Fine sandy soils weigh heaviest, while peaty soils are lightest inweight, But when saturated with water, a cubic foot of peaty soil weighs more than a cubic foot of sandy soil. Clay soils weigh less per cubic foot than sandy soils. The larger the amount of organic matter in a soil the less the weight, Pasture land, for example, weighs less per cubic foot than arable land. Weight is an important property to consider when the total amounts of plant food in two soils are compared. A peaty soil containing 1 per cent, of nitrogen and weighing 30 pounds per cubic foot has less total nitrogen than a soil containing 0.40 per ce...