“Wise water management requires knowledge of how much water the crop needs and when that water is needed,” Schmidt says. “More effective irrigation scheduling can help producers to better match the timing and application of irrigation with crop water use.”

In a paper to be presented later this year at the American Society of Agricultural and Biological Engineers’ national irrigation conference, the researchers note that irrigation in hot, humid areas is “particularly challenging,” because water must be applied in a timely manner to prevent yield loss due to crop water stress, while avoiding flooding should rain occur following an irrigation.

Also, it is difficult to detect the onset of crop water stress under environmental conditions that limit evaporative cooling.

The irrigation decision support system is based on calculations of crop water use from weather data collected from weather stations throughout Mississippi, using crop coefficients developed from weighing lysimeters.

A “checkbook” method is used to indicate when supplemental irrigation is needed, based on water available to the plants and crop water use. The method is very similar to a check book, with inputs to the available soil water from rainfall and irrigation being “credits”, and use of soil water by crops being “debits”. As the daily soil water balance decreases with crop growth, the loss of soil water to a predetermined negative balance indicates the need to irrigate.

The tool will be integrated with other publicly available, spatially registered farm and soil databases to reduce the amount of data the farmer needs to enter, and develop the irrigation scheduling recommendations. It calculates crop water use and suggests a need to irrigate based on the irrigation system and the allowable deficit set by the producer. Key data needs and calculations include weather data, crop coefficients, estimated soil runoff, and soil information.

The irrigation decision support system will be delivered to producers through an easy to use and readily accessible format. Training materials will be developed and presented to producers through on-site training and other Extension systems.