WSP00118 - Laserfiche WebLink

Home Browse Search

. . ~ DEPARTMENT. OF PUBLIC. WORKS 225. Table 7 shows the' weights. per cubic foot of each foot section of soil to six feet, .for the several points where determination was made. Absolute' specific' gravities were determined on ten samples and were found to avrage 2.65. Some Water Relations of Soils. When water is added to land, either as rain or thru irrigation, a portion of it is drawn into the TABLE NO" 7.~Weight per Cubic Foot, Based On Valne8 Taken from Cn.....e. .Average Norman Foot Hastings No.rman . Holdrege Bertrand Holdrege Ke,neaaw . .- '-'Bertrand 1 73.8 80.1 84.2 79.3 81.2 81.6 2 78.6 .83.6 89.6 86,7 : 86.6 94.2 .3 82.0' 90.9 ". .91.5 91.8 91.4 94.6 4 78.4 88.7 86.7 90.8 88.7 78.9 L. 5 '76.6 81.7 82.4 86.6 83.6 80.2 6 77.2 80.0 82.6 84.6 . 82.3 87.7 Ave. 77.8 84.2 .86.2 ~6.6. . 85.6. 85.4 1-". r soil by capillary forces. Another portion may spread over the surface l<S runoff and imm~diately a portion . is lost'thru evaporation. Obviously these amounts vary with each and every factor that affects . them, the' principaleones being the type <if soil' and the rapidity with which the water is applied. After the water is in the soil there is always some loss thru direct .evaporation, the. water escaping as v3,por...If there is sufficient water present and no 'imperVlous strata in the soil, .some. water.. may penetrate so deeply into the soil that it will .be beyond recovery by... plant roots. Another portion is held within the soil by the forces of . capillarity and is, under ordinary conditions, last. largely by being drawn out of the soil by growing vegetation. It is from the water held by capillarity that the plants obtain their supply for making growth. Not all of the capillary water however is available for crop lIse.. As the soil beconles drier a point is reached. when the force exerted by the plant to obtain water is no greater than the capillary power of the soil. The amount of water below this paint is non- a'-ailable and is . quite frequently spoken of as hygroscopic. These moisture relations of soils are important in the present study and the factors determining them are quite constant for a given type of soil. In the proposed irrigation project three 'questions concerning water I'elations of the soil are of primary importance. First,-how rapidly will the soil take in water and how effectively can water be spread over a field? Second,-how much water Will the soil retain? Third,- how much of the water retained by the soil can be utilized by growing plants? . .. ~1