Monday, November 13, 2006

Low-pressure, Drip-irrigation for Rice.

Brian Ottis1, Joseph C. Henggeler1, and Earl Vories2. (1) University of Missouri, "PO Box 160, 147 State Hwy T", "PO Box 160, 147 State Hwy T", Portageville, MO 63873, United States of America, (2) USDA-ARS, Delta Research Center, P.O. Box 160, Portageville, MO 63873

Rice production accounts for a large amount of water use in southeast Missouri.  Typical irrigation rates average 75 cm per acre per year, and in extremely dry years, can exceed 125 cm.  In other rice production areas, such as the Grand Prairie of Arkansas, some rice producers pump water from depths of more than 600 feet.  Additionally, water tables are dropping and water quality is decreasing in some areas.  Fortunately, southeast Missouri has ample water supply and good water quality; however, restrictions may be on the horizon due to potential water policy changes and urban competition for water.  It is important that alternative irrigation methods for rice be investigated in the event such changes take place.  A study was established at the University of Missouri Marsh Farm in 2005 and 2006 to evaluate low-pressure, subsurface drip-irrigation for rice.  Three popular Southern long-grain rice cultivars (Cocodrie, Wells, and CLXL8) and four nitrogen (N) rates (67, 112, 157, and 202 kg N/ha) were evaluated.  Results in 2005 indicated that subsurface, drip-irrigation reduced irrigation inputs by 80% compared with conventional flood-irrigation; however, this study was established on a non-conventional rice soil with excellent drainage.  Rice maturity was delayed 2 wk with drip-irrigation compared with conventional flood-irrigated plots; however, no yield differences were observed between the main effects of irrigation technique, with only minor milling quality reductions with drip-irrigation.  Subsurface drip-irrigation appears to be a valid alternative to conventional flood culture based on water savings and yield data collected in 2005; however, factors that may affect the commercial viability of this system include price of installation, tillage, long-term stability of the dripper lines, and rutting during harvest.  Benefits of such a system include the elimination of levees, elimination of airplanes for pesticide and fertilizer applications, and substantial water savings.