Determining Irrigation Scheduling for Cotton and Peanut Using Cropping System Models

Abstract

Irrigation scheduling is an important management practice for farmers who grow irrigated crops. Effective irrigation is possible by regular monitoring of soil water and crop development conditions in the field. However, this methodology requires frequent field visits and, consequently, it is time consuming. Computer simulation models can be an important aid for irrigation scheduling, as they integrate the soil-plant-atmosphere complex. The main objectives of this study were to determine the impact of different irrigation scheduling regimes on cotton and peanut growth and development and to evaluate the application of a crop simulation model as a tool for irrigation scheduling. Two experiments were conducted in four rainout shelters, located at the Griffin Campus of The University of Georgia, during 2005 and 2006. Cotton was grown in 2005 and peanut was grown in 2006. The CSM-CROPGRO-Cotton and CSM-CROPGRO-Peanut models were used to define the irrigation treatments by estimating the timing of irrigation and the amount of water to apply. The irrigation event was triggered when the actual soil water content in the effective root zone dropped below a specific threshold of the available water content (AWC) and then irrigation was applied until the soil water reached 100% of AWC. The irrigation treatments corresponded to 30%, 40%, 60% and 90% of the irrigation threshold (IT). The models require daily weather data, including maximum and minimum temperature, solar radiation and precipitation as input. Actual