Management practices for control of quality and quantity of return subsurface flow were studied theoretically, in the laboratory, and full scale in the field. Field water management studies using waters of different qualities and different leaching fractions showed that the soil in the project area has a high salt buffering capacity. The soil acted either as a source or a sink for salt depending on the leaching fraction and the quality of water used for irrigation. Minimum average leaching fractions attainable on a field scale were found to be controlled by the uniformity of irrigation water application. Digital computer models were developed that consider properties of the soil, plant, water and environment. One model allows prediction of salt buildup and the yield response over several years. Salt buildup in the soil eventually caused a yield decrease. It was necessary to include a source-sink term in a salt flow model to accurately simulate field data. Source-sink phenomema observed in the field were confirmed by leaching tests conducted in the laboratory. Both models are potentially useful for salt management in the field.

"Prepared by Utah University, Department of Agricultural and Irrigation Engineering and Department of Soil Science and Biometeorology, Logan, Utah, under grant no. R-802864." Includes bibliographical references (pages 146-147).