|Ayars, James - Jim|
Submitted to: Proceedings 18th Congress of International Committee of Irrigation and Drainage
Publication Type: Proceedings
Publication Acceptance Date: 10/7/2001
Publication Date: 2/21/2002
Citation: Ayars, J.E., Soppe, R., Marani, A. 2002. Reducing irrigation in the presence of shallow groundwater using the cotton 21c model. Proceedings 18th Congress of International Committee of Irrigation and Drainage. No vol. or pgs. on CD ROM. Interpretive Summary: Controlling shallow ground water and disposal of saline drainage water are problems that plague irrigated agriculture throughout the world. One proposed solution to this problem is for salt tolerant crops to use water from the shallow ground water thus increasing the depth to water and reducing the total volume needing disposal. There is a need for water management techniques to schedule irrigations to insure that the crop uses water from shallow ground water. This paper describes the use of a cotton model to assist in scheduling irrigation of cotton. Results demonstrated that the model could effectively determine the need for irrigation and was instrumental in eliminating the final irrigation of the season without any negative impacts on yield.
Technical Abstract: A three year study on irrigated cotton in the Tulare Lake Basin, California showed the potential to eliminate the last irrigation of the growing season when cotton is grown in the presence of shallow groundwater. A physiological cotton model (COTTON2K) was used to predict the effect of the irrigation reduction on cotton lint yield. No lint yield loss was predicted or observed for the field with reduced irrigation. Reduction of irrigation did not result in a reduction of seasonal drainage water outflow from the subsurface drainage system in the experimental field. The soil has a high water holding capacity, and with a fully developed rootzone, enough soil water storage exists to avoid drainage from the last irrigation application. Reduction of irrigation did, however, result in a higher water use efficiency per unit of crop production. No difference in stored soil moisture was predicted by COTTON2K at the end of the season, since more biomass growth on the field receiving the extra irrigation resulted in a higher crop water use. The model was evaluated on crop response like crop height, leaf water potential and crop yield. Using a physiological plant response model as a decision tool for irrigation reduces problems encountered while modeling soil moisture processes in highly saline cracking clay soils. It also relates irrigation management directly to the goal of crop yield production.