LITTLE ROCK, Ark. -- Now is the time to decide if you are going to use multiple inlet rice irrigation (MIRI) this season. The potential benefits of multiple inlet rice irrigation include:
Quicker flood — improved fertilizer & herbicide efficiency
Reduced irrigation pumping time and costs
Reduced labor, runoff and cold-water rice
Maintain shallower flood and reduce stretching of rice
Avoid over-pumping top levees
Reduce effect of algae and scum buildup at spills
Free up labor and water for other irrigated crops
A recent survey indicated that multiple inlet rice irrigation was used on about 15 percent of the rice acreage during the 2002 season. Field comparisons of multiple inlet rice irrigation to conventional rice irrigation and grower surveys show an average water savings of 25 percent and an average labor savings of about 30 percent. The results have been varied, but multiple inlet rice irrigation demonstrations have been successful on fields that are steep, flat, big, and small and that have straight levees, crooked levees, small wells, big wells and soils ranging from sandy to gumbo.
You should consider trying multiple inlet rice irrigation on the fields that you have the hardest time irrigating. Fields with limited irrigation water or that are hard to get flooded in a reasonable number of days and fields that are difficult to keep the bottom levees flooded are usually helped by using multiple inlet rice irrigation.
With increasing energy prices, fields that have traditionally had high pumping costs might be good candidates for multiple inlet rice irrigation.
Multiple inlet rice irrigation could possibly reduce losses in fields that have a significant amount of yield loss due to cold-water effect each year.
The basic approach to multiple inlet rice irrigation is to place irrigation tubing across the field and punch holes or install gates for water inlets to each levee that the tubing crosses. The holes or gates are adjusted when flooding the field so that each levee floods up at about the same rate.
Most growers find that after the initial adjustments they don't have to spend as much time with the water management as they do with most fields that are irrigated conventionally.
The heavier 9- or 10-mil tubing should be used. It can be placed down the side of the field, out in the field, over levees or down an elevated pad or turnrow.
Characteristics like field size and slope, levee pattern, water location and flow and grower preference determine how the tubing is laid out. Running the tubing down the side of the field and straight over the levees seems to work best in many cases.
The Water Management Section of the Arkansas Rice Production Handbook, MP 192, covers other considerations and recommendations that could help answer questions about using MIRI. The handbook is also available on the University of Arkansas Extension Web page at University of Arkansas Extension Web page  under publications.
Arkansas county Extension agents might also be able to provide information from their experiences with multiple inlet rice irrigation demonstrations that they have helped conduct in the county. It might be possible that they could assist with a multiple inlet rice irrigation demonstration this season through the support of the Rice Research Promotion Board. They could also share the names of growers who might provide some beneficial advice from their experience with multiple inlet rice irrigation.
Multiple inlet rice irrigation is not going to work on all rice fields, but experience indicates that it has the potential to be used successfully on a lot of acreage. Field demonstrations being conducted by Extension and others help determine where and how growers can implement it best.
Growers say it is one of the most helpful rice production practices to come along in recent years.
This is the first of several articles that I plan to do this year on drainage and irrigation water management. I hope to provide information that will be timely and helpful. If you have questions or suggestions on topics please contact me: Phil Tacker, 501-671-2267 (office), 501-671-2303 (fax), 501-944-0708 (cell), or [email protected]  (e-mail).
Phil Tacker is a University of Arkansas Extension ag engineer.