By Chuck Burr and Daran Rudnick
Climate variability is something all farmers deal with in most years. One of the main weather extremes that impacts irrigation management is extended periods of dry conditions, or drought.
Drought can increase daily crop water use due to lower relative humidity and is often accompanied by higher temperatures. When managing under these extreme conditions, irrigators need to understand daily and seasonal crop water-use patterns, and adopt practices and technology that result in more bushels of grain per inch of water applied.
Here's a look at some “weather ready” adaptation strategies for irrigation management:
• Schedule irrigation based on soil water data. The 2013 USDA Census of Ag Farm and Ranch Irrigation survey indicated that only 23% of Nebraska irrigators use soil sensing as a basis for irrigation scheduling. This number needs to increase to improve irrigation water-use efficiency.
With the technology available today, irrigators can move away from using the feel of the soil (44%) as a scheduling method.
Information on selecting and using soil water sensors is described in two Nebraska Extension publications: Soil Water Sensors for Irrigation Management (EC3002) and Principles and Operational Characteristics of Watermark Granular Matrix Sensor to Measure Soil Water Status and Its Practical Applications for Irrigation Management in Various Soil Textures (EC783).
• Conserve water by decreasing evapotranspiration. About 30% of crop water use is due to evaporation, and evaporative losses are highest early in the growing season prior to canopy closure. Reducing evaporation via no-till or reduced tillage, and narrower row spacing can leave more water available for transpiration, which is the driving force for yield production.
Research at the University of Nebraska-Lincoln has shown that corn and soybeans can be stressed during vegetative growth stages without significantly affecting yield. This may leave more water available for grain fill.
• Get soil covered. Leaving crop residue or using cover crops can increase infiltration of precipitation and irrigation. Also, improving soil structure can lead to higher amounts of precipitation being stored in the profile. This increased storage would be available for crop production, potentially helping meet crop water demands in excess of irrigation capacity during droughts.
In addition, increasing infiltration and water-holding capacity can allow for increased irrigation application amounts, as water is less likely to run off. This decrease in the number of applications is beneficial to reduce canopy evaporation and get more of the applied water into the soil.
Burr is a Nebraska crops and water Extension educator. Rudnick is a Nebraska Extension irrigation management specialist. This report comes from UNL CropWatch.