This paper is an introduction to the Advances in Irrigation Special Collection in this issue of Transactions ASABE and the next issue of Applied Engineering in Agriculture of 14 papers selected from 88 papers and presentations at the ASABE 5th Decennial National Irrigation Symposium, December 2010, in Phoenix, Arizona. This symposium followed the objectives of the previous four decennial events to provide a forum to assess progress of research endeavors to advance the effectiveness of irrigation practices during the past 10 years, leading to further research priorities that respond to future challenges. The papers in this Collection address a wide range of topics grouped into broad categories: microirrigation, center pivot irrigation, crop water use for improved irrigation management, and smart irrigation controllers for landscape irrigation. While these papers are not inclusive of all irrigation work since the last decennial symposium, they do provide a snapshot of work considered important by researchers, funding agencies and other stakeholders. Many aspects of irrigation have changed since the first symposium in 1970. Although microirrigation is a small proportion of irrigated acreage, it will continue to increase in highly technical commercial food and fiber production as well as in subsistence farming. Center pivot irrigation systems have been an important tool to deliver water more efficiently in diverse settings. Advanced telemetry and control systems, developed during the past 10 years, are now common options for center pivots, but challenges remain to integrate those hardware developments into crop management practices. Possibilities are emerging for adding monitoring devices to center pivots to match crop water needs with water delivery. Energy balance models continue to be refined as tools to estimate crop water use from both ground and satellite based data. Evapotranspiration estimates are evolving from single location weather stations to whole-field or regional scopes. Finally, “smart” irrigation controllers have coupled evapotranspiration estimation or soil-water sensing with automated irrigation system water delivery. These controllers can increase the precision of irrigation to match crop or landscape water needs. Irrigation will continue to be an important practice for producing the world’s food. The irrigation research and education professions will need to respond to food production challenges with even more refined irrigation systems and water management in the next 10 years. However, research investment in irrigation continues to decline when important issues exist, such as: maintaining agricultural profitability with declining water supplies, integrating sensor-based information for real-time autonomous or semi-autonomous management, competition for limited water supplies between agriculture and other sectors, increasing energy cost, environmental impacts of irrigation, and use of alternative water sources (i.e., lower quality) for irrigation
