NESPAL > Water Use & Quality > Research Projects > Irrigation Technology and Management

Irrigation Technology and Management
by Jim Hook

NESPAL programs must be built upon a solid foundation of discovery and technology enhancement. Agriculture water use for irrigation is predicated upon alleviating yield reducing water stress in crops using economically sound water application technologies. Irrigation in the humid areas like the Southeast US was once thought to be a means to make up for the deficit rainfall during drought seasons to protect normal yields. Labor limitation imposed by portable pipe and towable traveler systems and water supplies limited to on-farm ponds effectively established that notion, one that still persists outside of the farm community.

Introduction of deep wells that could extract copious supplies from the abundant Floridan Aquifer and labor saving center pivots altered that picture forever. The high costs associated with these effective and efficient irrigation systems required a return on investment that was greater than yields protected while making normal dryland yields of corn, soybean, cotton, and even peanut. However, the modern systems of the 1970's also offered opportunities to greatly increase yields to the crop potential and opened new market possibilities like vegetables.

While most of the U.S. continues to convert to center pivots for substantial improvements in irrigation, Georgia farmers have begun to realize that even these systems are not as cost effective and water efficient as they need to be to remain competitive with more limited water supplies. Back-to-back drought have taxed even the best systems. Irregular field shapes meant that many center pivot systems had to be inefficiently small, operated in partial circle, or fields modified to include unsuitable soils to make complete circles. The earliest systems were equipped with energy wasting high pressure pumps and sprinklers that spread water widely, much of it lost to wind drift and evaporation.

In response to these problems NESPAL, and CAES departments established field and laboratory-based research projects to improve application technologies and irrigated crop management:

Crop Response to Water
Cost effective irrigation begins with an understanding of the impacts of various water stress intervals and timing on yield and quality. While the costs of inputs including irrigation equipment, well drilling, capital financing, as well as energy, land rent and, in some cases, water, vary over time and commodity prices fluctuate, a single "best" irrigation schedule or recommendation cannot be made. However, by creating a relationship between crop growth and yield with available water and climate, we can make recommendations as prices change. Those relationships defining crop response to water are best encoded in multivariate models such as those in DSSAT. Studies that have been conducted in the past have been compiled and data made available via the NESPAL Irrigation web site for researchers around the globe to develop and test the models.

With new facilities coming on line in Georgia, new crop response studies will be initiated, including water relations and quality for a number of important vegetables. The emphasis in these studies is a comprehensive examination of crop response to water that can guide future irrigation decisions by farmers and future water resource management decisions by permitting agencies.

Throughout these studies, education of farmer and non-farm water regulators as to crop water needs and efficiencies in land, labor, and agrichemical inputs achieved with irrigation.

Irrigation Scheduling Technology and Management
When water costs less than labor required to monitor crop water needs, farmers tend to simply guess water needs. With low value crops they will tend to err on the short water side and yields can suffer. When crops are valuable like vegetables, irrigators tend to err by overwatering, not taking any chances on a water stressed crop. The low cost of fuel combined with the "unlimited" amounts of water that can be withdrawn in Georgia meant that it was more cost effective for farmers to guess than measure water needs.

While the future of irrigation water supply and water markets are uncertain, limitations already imposed on new water withdrawals for mst of the irrigated regions in Georgia now place a premium on effective use of what is withdrawn. Likely increases in energy costs and mandated limits on water withdrawals may quickly send farmers looking for cost effective and water saving irrigation schedules.

Where close attention is needed, monitoring crop, soil, and/or weather will become necessary. The research efforts of NESPAL are to develop and evaluate new technologies to remotely monitoring these parameters. Coupled with crop response models, they will be used to provide cost-effective, practical irrigation scheduling that will improve efficiency of crop water use.

Technologies for Efficient Application of Water
This Southeast project led by Biological and Agricultural Engineering focuses efforts of engineering, agronomy, and new technologies on evaluation of most effective systems to deliver water to crops. It ties aerial/GIS assessment and farm surveys that identify existing systems and problems with efforts to evaluate efficient application alternatives to existing irrigation systems. Best Management Practices (BMP's) and costs for implementing them in Georgia were estimated by a panel of scientists and engineers. That state of the art information was assembled in web form on our irrigation pages. New thrusts in this arena will begin in 2002 with completion of new irrigation research facilities at C.M. Stripling Irrigation Research Park, Camilla, Ga., and Lang Farm, Tifton, Ga., and be coordinated with other studies by ARS in Shellman, Ga, and by Auburn, in Headland, Al. With more than 10,000 center pivots in place, the most effective strategy is to identify cost-effective, water saving modifications for existing pivots. Other alternatives will also be examined under a range of conditions, including traveler systems, soild set, drip, and subsurface drip (SDI).