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item Halvorson, Ardell

Submitted to: Biological Systems Simulation Group Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/21/2006
Publication Date: 4/11/2006
Citation: Halvorson, A.D., Hergert, G.W., Schlegel, A.J. 2006. Managing for efficient use of limited irrigation water: current practices, research needs, and potential role of models. Abstr., 36th Biological Systems Simulation Conference, April 11-13, Fort Collins, CO.

Interpretive Summary:

Technical Abstract: Water is becoming a very valuable and limited commodity in the central Great Plains area in eastern Colorado, western Nebraska, and western Kansas. Water used for irrigation of agricultural crops is being diverted to urban use to accommodate the increasing human population along the front-range of the Rocky Mountains. Sprinkler irrigations systems have been installed in the central Great Plains to irrigate land formerly furrow irrigated or that was formerly dryland. The increased pumping of water from the aquifers and reservoirs for irrigation has caused a decline in water tables, such as the Ogallala aquifer located in the eastern part of the central Great Plains. The decline in water table level not only increases pumping and production costs, but also jeopardizes the future of irrigated agriculture in some areas. Thus, managing available water supplies for optimum yield, quality, and economic returns becomes a critical management factor for producers. With reduced water availability, the question becomes how do producers utilize a limited quantity of water to achieve the highest economic yields on his or her farm. Limited water supplies need to be applied at critical crop growth stages to optimize crop productivity and yield. Research shows that for many grain crops, water application during the reproductive and early grain fill stages is critical. There must be sufficient stored soil moisture or precipitation up to this time, however, to provide sufficient growth and yield potential to produce a crop. Thus, reducing water application during the vegetative production period of crops and applying it during the reproductive stage may be a critical management decision that will result in improved water-use efficiency (WUE). The strategy for other crops (forages, root crops, vegetables) is not certain because there has been limited research. Forage crops have a different water timing need than grain crops. Forage crops require water during the vegetative production period to optimize biomass production, thus requiring early season rather than late season application of irrigation water to optimize WUE. Research is needed to determine the effects of water stress at various growth stages on final grain, forage, or produce yield of crops grown in the central Great Plains, as well as other irrigated areas. Developing sufficient data for a wide range of irrigated conditions across the U.S. is difficult. Models have the potential to integrate the research data, extrapolate beyond specific sites, and help producers with limited water supplies make management decisions on how to most effectively utilize available water for greatest economic returns. This paper presents examples of current management practices that can be used to optimize WUE when limited water supplies are available. Halvorson et al. (Proc. Great Plains Soil Fertility Conf., 2006) compared drip vs. furrow irrigation systems for onion production near Rocky Ford, Colorado. A total of 27 inches of water was applied to the onions in 20 irrigations compared to 96 inches of water in 13 irrigations with the furrow irrigation system. Onion yields were greater with the drip irrigation system than with furrow irrigation. Application of N fertilizer increased onion yield and onion size, with the drip system producing higher onion yields with less N applied than with the furrow irrigation system. Gross economic returns, after adjusting for cost of drip system, water, and N fertilizer, were greater with the drip system at low N rates and equal to the furrow system at high N rates. This study points out that irrigation system and management of plant nutrients, especially N, can play an important part in maximizing WUE. Halvorson et al. (Agron. J. 98:63-71, 2006) showed that N fertilization rates that optimized corn grain yields also optimiz