AuthorROTH, ROBERT LEROY.
Soils, Irrigated -- Mathematical models.
Soil moisture -- Mathematical models.
AdvisorLaursen, E. M.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractTrickle irrigation is the latest technique to efficiently apply irrigation water to plants. It is selected over other irrigation systems when water is scarce or expensive, the soils are very permeable or cannot be leveled, and crop values are high or require specialized cultural practices. Trickle irrigation is also very popular in commercial landscaping because of its ease for automation. Plant growth is optimized when the soil water content is near field capacity so that adequate water and oxygen are available to the plant root. Thus, the knowledge of moisture movement from a point source is most critical in designing, operating and managing a trickle irrigation system. This knowledge could help improve the irrigation efficiency so that maximum growth and production could be achieved per unit of water. A simple procedure was developed which reasonably predicted the wetted soil volume, lateral movement and vertical movement of water from a point source. The underlying assumptions are that the soil moisture in the wetted profile approximates field capacity and trickle irrigation is defined to exclude large flow rates which would cause excessive ponding and surface runoff or small flow rates which would not increase the soil moisture so it can approach field capacity. Moisture contents in excess of field capacity would be lost to deep percolation because of gravity. This procedure was verified with field tests on a Superstition Fine Sand soil and in the laboratory on a Gadsden Clay soil. The moisture movement in the soil from a trickle source is more a function of the water volume applied than the rate at which it was applied. Higher flow rates can cause greater moisture contents in the soil during the application but the values decrease and approach water contents from lower flow rates if given similar redistribution periods. It is expected that the procedure for predicting wetted soil volume, lateral movement and vertical movement can be used by both designers and managers of trickle irrigation systems. Estimates of the soil moisture contents and volume of water applied are needed. Greater accuracy in predicting the moisture movement can be attained by some simple measurements in the field. The procedure resulting from this study is more advantageous over the mathematical models which require complicated unsaturated hydraulic conductivity functions and high-speed computers to solve them.
Degree ProgramCivil Engineering