By Joel Peru, PAg, CCA, Irrigation Agrologist, Outlook
Intensive irrigation lets producers apply water to their crops when, and if, it is required. Consequently, irrigation scheduling is important to maximize crop yields and ensure sustainable water use. Proper irrigation scheduling will improve a farm's profitability and efficiency by maximizing crop yield and quality, decreasing water loss through deep percolation and surface runoff, and reducing pumping costs. Determining when to irrigate during a growing season is dependent on many factors. The importance of these factors is key for producers to maximize their return on investment.
Before scheduling irrigation, there are four things you need to know: soil texture, soil water-holding capacity, soil moisture content and crop water use at the specific development stage. The capacity of the irrigation system also needs to be considered. Different crops use different amounts of water throughout the growing season; crops require different amounts of water during different growth stages. For example, canola can use seven mm per day during pod fill but only use two mm per day during the rosette stage. Another crop such as peas will use a maximum of six mm per day during pod development and will not use more than two mm per day until June if planted on May 15.
The three methods of irrigation scheduling involve plant-based, soil-based and crop water use (evapotranspiration) based methods. The soil-based method is desired in Saskatchewan as it predicts water requirements before drought stresses occur. Soil moisture measuring is key for the soil-based method as it determines the volume of soil water currently available to the plant. Once an irrigator knows the amount of water available in the soil and the evapotranspiration rate, the timing for next irrigation can be estimated. The three ways to estimate/measure soil water storage include feel by hand, moisture monitoring equipment, and computer models based on weather data. Most irrigation scheduling only requires a couple rain gauges, a Dutch auger and knowledge of your crop and soil properties.
Remote techniques that transmit reliable data from the moisture measuring instrument in the field to hand-held electronic devices are currently available. Irrigators can use on-site field moisture measurement with rainfall data, use a check-book approach or a computer modeling program to predict crop water use. New tools have been developed to automate the process of data collected by field monitoring devices. Remote moisture sensing will become more common as the technology advances and becomes more affordable.
More information can be found in the recently updated the Irrigation Scheduling Manual.
The Irrigation Crop Diversification Corporation provides updates of weekly crop water use throughout the growing season, follow @ICDC_SK on Twitter for regular updates.
For assistance please contact an Irrigation Agrologist at 306-867-5500.