Conserving water resources and reducing irrigation-related production costs are great reasons to improve irrigation efficiency.  An increasingly important irrigation efficiency motivation for many growers, however, is mitigating the effects of limited and declining irrigation water availability. Regardless of the primary goal, effective and efficient irrigation management is essential to maximizing water use efficiency in crop production.

Water use efficiencyis determined by the harvestable yield of a crop per unit of water used or applied. Increasing the water use efficiency can be achieved by producing more crop yield for a given amount of water and/or maintaining crop yield with less water.  While water often is the limiting factor to crop yield, particularly in arid and semi-arid production regions, it is very important that water management is considered in the context of the overall crop production system. 

If the cropping system is restricted primarily by limited water capacity, optimizing water management can result in increased crop yields and/or quality.  However, irrigation alone will not solve every problem.

Crop rotation

Consider crop rotations and variety selections to mitigate risks associated with water quality (salinity) issues as well as pest pressures.  Adopt good Integrated Pest Management practices to address insect, weed and disease concerns. Apply Integrated Crop Management strategies to optimize fertilizers and other inputs. 

Advanced irrigation application technologies, including low pressure center pivot irrigation (Low Energy Precision Application – LEPA; Low Elevation Spray Application – LESA; Mid-Elevation Spray Application – Mesa; or Low Pressure In-Canopy - LPIC) and micro-irrigation (including Subsurface Drip Irrigation) can be managed effectively to achieve high application efficiency and excellent distribution uniformity.

Operating at relatively low pressures, they require less energy (and therefore lower cost) per volume of water than high pressure sprinkler methods.  With good management, they can also deliver water with lower evaporation losses than high pressure sprinkler systems and result in lower surface runoff and deep percolation losses than surface irrigation. Hence they can bring about both energy and water savings, or at least increased energy and water efficiency.

Best Management Practicesinclude irrigation scheduling to better match timing and rate of water available to crop water requirements, as well as strategies to minimize water losses through runoff, evaporation, and deep percolation (leaching).

Irrigation schedulingis essential to increasing water use efficiency. Techniques commonly used to determine “when” and “how much” to irrigate include weather-based methods, soil moisture monitoring methods and plant indicator methods. Weather-based evapotranspiration “ET” models apply local weather data and crop-specific information to provide accurate estimates of crop water use.  This information is made available by regional ET networks and delivered through e-mail, fax and/or internet.  Soil moisture monitoring includes an array of methods, from the hand sampling “look and feel” method, to tensiometers, to granular matrix and gypsum resistance blocks, to capacitance and time domain reflectometry sensors.  Soil moisture monitoring methods vary widely in cost, relative convenience, applicability and ease of use.