By Daran Rudnick
Extension Irrigation Management Specialist
Figure 1. Adapting irrigation management strategies to maxmize effciency for crop growth can help farms through periods of extreme weather variability, such as dry periods or droughts.
Climate variability is something all farmers need to react to in most years. One of the main weather extremes that impacts irrigation management is extended periods of dry conditions, commonly referred to as 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, as well as adopt practices and technology that result in more bushels of grain per inch of water applied.
Adaptation Strategies
- Schedule irrigation based on soil water data. The 2013 Census of Ag Irrigation survey indicated that only 23% of Nebraska irrigators use soil sensing as a basis for irrigation scheduling. This number needs to increase if we are to improve irrigation water use efficiency. With the technology we have available today, we need to help irrigators 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 during vegetative growth stages. Approximately 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 or reduced tillage, narrower row spacing, etc. can lead to more water being available for transpiration, which is the driving force for yield production. Furthermore, research has shown that both corn (Rudnick et al. 2017) and soybeans (Payero et al. 2005) can be stressed during vegetative growth stages without significantly affecting yield. This may leave more water available for grain fill.
- Residue cover/cover crops can increase infiltration of precipitation and irrigation. In addition to infiltration, 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 runoff. This decrease in the number of applications is beneficial to reduce canopy evaporation and get more of the applied water into the soil.