Show scientific CULTURE OF SOIL interesting Inte paragraphs taken fi from rom prof Tin article on soil moisture different terms that the philosophy of scientific c sall soil cu culture iture may be thoroughly understood the following lowing lol paragraphs are from an article written by prof J D tinsley of the new mexico experiment station water in the soil may take the form of free water capillary water or hygroscopic water 1 free water is water under the influence of gravity percolating through the spaces in the soil and seeking a lower and lower level ultimately it forms films around the soil particles and fills in the minute spaces between them in this condition it no longer tends to sink deeper into the ground it is no longer influenced by gravity it has in fact ceased to belfred bel be free water but has become capillary water when every soil grain has been bee covered with a film of capillary water and all the spaces are filled the soil is said to be saturated it will hold no more and any excess isaree is free water sinking deeper into the soil and saturating it to still greater depth the capillary water is held to the surface of each minute grain of soil by the force of adhesion its tendency is to move toward the place where the soil is drnest whether that be u up p down or horizontally this movement m ent along the soil particles is similar simm to the movement of oil along a lamp wick and is what is meant I 1 when the term capillary attraction 0 o or r capillarity is used if one end of a small tube be immersed in water jt it will be noticed that the liquid will rise ride higher in the tube than in the vessel in which the water is contained this also is due to capillarity experiment shows that the smaller the tube the higher the water will rise but the larger the tube the faster the movement now the soil may be imagined as filled with multitudes of these tiny tubes through which capillary water rises to the surface when the surface becomes dry enough to attract it this force of capillarity Is the one thing upon which the farmer must depend to bring the water in the soil cose enough to the surface to be reached by the roots of crop plants at the same time his bis greatest care must be to prevent the moisture from being lost by evaporation which proceeds with extraordinary rapidity in the excessively dry atmosphere of semiarid semi arid america from the capillary water the plant roots derive their supply of water anti and with it they take up the soil elements necessary to their growth the third form of soil moisture Is hygroscopic water this is water that cannot be dried out or removed from the soil by natural evaporation it is a wholly negligible quantity |