Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)



First Advisor

M.L. Horton


This investigation is an evaluation of methods of analysis of water conserved during off-season periods and evaluation of the effect on the subsequent crop. Energy and water shortages during the midsummer peak irrigation season have forced farmers to consider the possibility of irrigation at times other than peak growth stages as an alternative practice. Dryland farmers are interested in the benefit of water conserving cultural practices such as summer fallow and snow trapping. To evaluate the benefit of these off-season practices, a yield function based upon water availability is necessary. In order to better understand the effects of off-season irrigation and other cultural practices, a theoretical analysis using the basic flow equation is beneficial. In this study consideration was given to: (1) development of a method for determining the feasibility of fall irrigation and off season cultural practices, (2) development of a yield function for corn based upon water availability at different physiological stages of growth, (3) development of a theoretical mathematical simulation procedure for examining moisture movement under field conditions. Moisture profiles of irrigated and nonirrigated plots of corn, wheat and alfalfa were monitored over a winter and through a growing season. Data collected were used to develop a function to predict the effective amount of spring carry-over from a fall irrigation. Data collected during the growing season were used to determine the response of the corn crop to several magnitudes of stress at different physiological stages of growth. A mathematical simulation of a soil moisture profile under field conditions with simplified boundary conditions was performed. Verification of the simulation was accomplished using measured field water contents. Results indicate that fall and/or early spring irrigation applied to a deep fine-textured soil can cause crop yield depression during years of greater than average fall, winter and early spring precipitation. The simulation of field water movement resulted in soil water profiles that were adequate representations of field plots.

Library of Congress Subject Headings





South Dakota State University