OCR Text |
Show TALK ON CAPILLARITY Moisture Steadily Transferred From One Particle to Another. When Surface of Soil Is Left Undisturbed Undis-turbed Tubes Come Close Together, Togeth-er, Allowing Water to Pass From One to Another. Now capillarity is a big word, and It means something pertaining to a hair. Now hair has very little to do with the soil and yet "capillarity of the soil" is a common term. Very fine tubes are called capillary, or hair like tubes, and the word capillary is often applied wrongly because we have no better word to express the meaning. For instance, take two sheets of glass and place them in a pan of water, and the water will flow up between them far above the level in the pan, and if the glass is not too long, it will run over the top, writes John Isaac in the Town and Country Journal. This Is called capillary capil-lary attraction. Place a piece of woolen wool-en rag In a pan of water and leave one end of it over the side and the water will run up the cloth and over the rim of the pan. This, too, is called capillary attraction, yet In neither case are their any hairs or hair like tubes. Now, in the soil we often speak of the loss of moisture by capillarity capil-larity or capillary attraction, and of capillary tubes through which the water wa-ter escapes, but there are no such tubes and no continuous passage between be-tween the lower moisture in the soil and the surface. But there Is a constant con-stant flow of water through the soil, and this moisture Is being steadily transformed from one particle par-ticle to another. Now when the surface of the soil Is left undisturbed these particles come very close together, to-gether, and the closer they lie together to-gether the more easily the water passes from one to the other. So If the ground Is left it compacts, that is. the soil particles come closer together; to-gether; this forms a very close connection con-nection between the surface and the lower layers, and between these closely compacted particles there are minute spaces through which the water raises with comparative rapidity, rapid-ity, this comes to the surface and is evaporated by the sun, so that it Is lost to the soli and we say the ground is dry. In 6peaking of this process It is often said that the moisture escapes es-capes through capillary tubes, although al-though as you see, there are no tubes at all, only a close connection between be-tween the minute soil particles, which Is Just as bad, for It affords a continuous passage for the water to come up to the surface and be lost To prevent the escape of this moisture too rapidly, some people apply what Is known as a mulch to the soil, or to such parts as they wish to protect. This is some kind of covering, cov-ering, straw or other, which will shade the ground and prevent the evaporation of the water by the stjn. This, of course, does not prevent the tens of thousands of little pumps which are at work on every square foot of the soil from bringing the moisture to the surface. To cheek this loss and prevent too much of the water from escaping, we resort to what is called "cultivation." That Is we keep the surface always broken up; keep stirring the top soil, so that the connection between the soil particles is broken up and prevented pre-vented from being continuous. This forms what Is called a dust mulch, or a dust covering, and if this Is kept from compacting, it prevents the formation for-mation of continuous passages for the water which Is kept In the soli, until it flows past the trees and plants whose roots take it up and use It for building up their tissues and making fruit and grain, It does not take long for thp particles to settle close together to-gether again, so that they require frequent fre-quent stirring up. |