Irrigation Scheduling
A readily available source of water for irrigation is essential for viable crop production and landscape maintenance in the arid southwest. In San Juan County, New Mexico, the amount of water available for irrigation depends upon the depth of precipitation, particularly winter snowfall that occurs in the San Juan and La Plata Mountains of southwest Colorado. Recurring droughts and ever-increasing demands for this water may decrease the amount available for irrigation, in the future. Consequently, it is important that irrigation management plans be developed to mitigate potential adverse effects of reduced water availability on crop production and landscape quality.
Efficient irrigation management requires an accurate estimate of a crop's water requirements or evapotranspiration (ET) during the plant's life cycle so that irrigation can be scheduled accordingly. While under-irrigation may reduce crop production and/or plant quality, over-irrigation wastes water, energy (due to excessive pumping), fertilizers and chemicals (due to increased weed and disease pressure and excessive leaching or runoff). As a result, production costs are increased, economic returns are potentially decreased, and environmental quality is degraded.
Since its conception more than 40 years ago, New Mexico State University's Agricultural Science Center at Farmington has evaluated relationships between irrigation (or ET) and crop production or quality. These studies have identified the ET requirements of various agricultural crops and landscape plants, including turfgrass.
Consumptive-use
Crop irrigation cannot be effectively scheduled without an estimate of the crop's daily water-use. This water-use, which includes both evaporation (water lost directly to the atmosphere from soil and plant surfaces) and transpiration (water transported from the soil to the atmosphere through plant tissues), is commonly referred to as evapotranspiration (ET) or consumptive-use. This presentation from the Four Corners Irrigation Workshop, that was held on May 2, 2007, briefly describes consumptive-use and provides some direction on ET estimation for crops of local interest.
Turfgrass
In the southwest, irrigation of landscapes accounts for approximately 50% of total domestic water-use in urban areas. Based on some surveys, more than half of this water could be conserved without adversely affecting the quality of existing landscapes if irrigation was carefully scheduled to satisfy plant needs (ET for acceptable quality.)
Irrigation Management for Water-wise Landscapes was presented by Daniel Smeal, NMSU ASC Farmington, on November 7, 2007 at the New Mexico Landscape Training 'Save Every Drop' seminar in Albuquerque, NM.
A study conducted at the Agricultural Science Center at Farmington, from 1998-2001, identified the water requirements of some cool and warm season turfgrasses. These findings resulted in the formulation of consumptive-use curves and crop coefficients that can be used to efficiently schedule irrigation on turfgrass.
The city of Albuquerque's Irrigation Audit Manual provides landscape managers and property owners with the concepts and tools necessary to develop a sound irrigation management plan. Here, it has been reproduced with permission granted by the Albuquerque Public Works Department, Water Resources Division-Water Conservation Office. The manual describes how to evaluate irrigation system performance, including water application uniformity, and explains how to efficiently schedule irrigation on turfgrass.