Drainage Manual A Water Resources Technical Publication

By U.S. Department of the Interior

prime requirement for successfully irrigated agriculture isthe development and maintenance of a soil zone in which the moisture-oxygen-saltbalance is favorable for plant growth. Plants require both moisture and oxygento live. When a saline water table rises and remains in the root zone longer thanabout 48 hours, resulting in an abnormally high saline moisture condition, agricultural production is usually seriously affected.The presence of oxygen in the interstices of the soil1 in the root zone is asnecessary as water for both seed germination and plant growth The oxygencontent of soil is governed by the rate of diffusion of oxygen through the soilpores. Also, the oxygen content is markedly affected by the moisture content ofa soil. Soils with initially low moisture content normally have relatively open porestructures between soil particles, allowing oxygen to freely permeate through theinterstices.A s the moisture contenti ncreasesw, ater displacest he air in the pores, thus forcing the air upward and into the atmosphere.O nce the oxygen is expelled, the oxygen content recovery rate is extremely slow in a soil that is in transition 'from a moist or wet state to a drier state. This slow recovery is caused by theinherently slow rate of diffusion of gases through such soils and the phenomenonof capillary stresses which develop in soils when the water content does notcompletely fill the voids. The proper balance between soil moisture and oxygenis maintained to a considerable extent by adequate draina

• Format: Paperback
• Language: English
• ISBN: 1539695360
• ISBN13: 9781539695363
• Release Date: January 1
• Publisher: Createspace Independent Publishing Platform
• Length: 342 Pages
• Weight: 1.01 lbs.
• Dimensions: 0.7" x 6.0" x 9.0"