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Show more freely through the soil. Earthworms also bring soil from lower levels to the surface, thus mixing the soil. In addition to earthworms, some rodents, ants, snails, spiders, mites, millipedes, centipedes, and various other worms and insects spend all or a part of their lives in the soil. The effect of these animals on the soil is beneficial for the most part. Because of their burrowing habits, for example, You will need 3 old- fashioned lamp chimneys or glass or plastic cylinders plus 3 small pans or low wide- mouthed glass jars, some thin cloth, and some string or rubber bands. Fasten the cloth over the top of the lamp chimneys or the cylinders. Turn them upside down and fill each three- fourths full with one of the following dry soils: 1. Sand. 2. Clay soil. This kind of soil is sticky when wet and dries in hard clods. Grind up the clods and put the dry clay in the chimney. 3. Dark, crumbly soil like that found under good grass sod. Or get topsoil from a garden or commercial nursery. Jar the cylinders slightly by bumping on a table to settle the soil. Be sure the soils are dry. Set the cylinders in the jars and pour water m the jars- do not pour water in the cylinders. Keep a record of how long it takes the water to move up 1 inch, 2 inches, and 3 inches in each cylinder. Note how long it takes for the water to reach the top or whether it ever reaches the top. The idea is to compare the capillary movement of water in coarse, medium, and fine soil particles. a lot of soil mixing takes place. They improve soil aeration and drainage. Some of them, however, feed on the farmer's crops. But it is evident that the animals in the soil are vital and contribute greatly to the way a soil functions. Soil- inhabiting plants and animals are largely responsible for converting the nutrients in undecayed organic matter to inorganic forms that growing plants can use. INTERPRETATION Moisture moves through soil in all directions, even against gravity, by capillary movement. This movement is caused by the attraction water molecules have for each other as well as the attraction between water molecules and soil particles. Water molecules cling together and form droplets in the air or on a greasy surface where there is nothing to interfere. But when a drop of water falls on soil particles, it spreads out as a thin film over the soil particles- because the attraction between the soil particles and the water molecules is greater than the attraction between the water molecules themselves. Water that moves through soil this way is known as capillary water. How far and how fast capillary water will move in a soil depends on the size of the soil particles and the condition of the soil. If the spaces around the soil particles are large, the attraction between the water molecules and the soil particles will not be enough to overcome the weight of the water and it will not rise appreciably; however, what movement it makes will be rapid because there will be little friction. This is true in sandy soils. On the other hand, in fine- textured soils the particles are closer together and the attraction between soil and water is greater. Water may then be expected to rise more slowly but higher in soils of fine texture. Under field conditions moisture moves from wetter soil to drier soil. The difference is not always great, therefore capillary water moves slowly and not far. Even so, enough moisture moves a short distance to the roots of growing plants to make it an important plant- soil relationship. Much soil moisture can be lost when capillary water moves to the surface and evaporates. Using mulches can reduce this. VIII. See How Capillary Water Moves Through Soil 10 |