ENGINEERING SYSTEMS TO ENHANCE IRRIGATION PERFORMANCE

The desirable irrigation system applies water at a rate that allows al l water to infiltrate and distributes the water in space and time to m atch crop requirements in each parcel of the field. Various types of i rrigation systems and management strategies have been developed in att empts to achieve the ''desired'' system. Our objective is to review va rious methods of enhancing irrigation performance. Although the ''desi red'' system has not been attained, considerable improvements have bee n made based upon selection and management technologies which generate profits within the constraints of environmental prudence. Each irriga tion system has inherent opportunities for enhancing irrigation perfor mance. Likewise, each has limitations in achieving maximum crop produc tivity per unit of applied water. Methods to improve the performance o r surface irrigation can be grouped into those that increase the unifo rmity of water intake, reduce runoff losses, or decrease spatial varia bility. Two surface irrigation systems that enhance performance are su rge-flow and level-basin. The uniformity and efficiency of sprinkler s ystems can be enhanced by computer-based design procedures and, in som e cases, by applying low-energy, precision application concepts. Advan tages of microirrigation are less surface area wetted, which minimizes evaporation and weed growth, and improved application uniformity whic h is specifically designed into the distribution network. An appropria te management strategy is necessary to attain the potential of an irri gation system engineered to match crop water requirements, and soil an d environmental conditions. The best irrigation method applies the amo unt of water desired at the appropriate time while providing for leach ing requirements, agronomic operations, and environmental consideratio ns. With enhanced engineering and computer capabilities and improved k nowledge of the soil-plant-water continuum, irrigators will adopt ''pr escription'' irrigation. Prescription systems apply precisely the pres cribed amounts of water, nutrients, and pesticides to match the produc tion capacity of each parcel of land.