RICE RATOONING - IRRI books - International Rice Research Institute

258 RICE RATOONINGResearch on rice ratooning in the U.S. has been very limited and has beenconcerned primarily with cultural practices and and with evaluating selections inbreeding programs for improved ratooning ability. U.S. literature on ratooning wasincluded by Chauhan et al in their recent comprehensive review of rice ratooning (7).Since widespread commercial ratooning was established in the Gulf Coastregion of the U. S. more than two decades ago, ratoon crop cultural practices havechanged very little. The proportion of Texas rice hectarage that is ratooned annuallyhas remained relatively constant; weather is the principal factor in year-to-yearhectarage fluctuations. Now, depressed economic conditions resulting frommarkedly increased production costs during the past 3-4 yr are causing researchers,producers, and industry personnel to review all aspects of rice production in an effortto optimize profitability. Economic analyses indicate that ratoon cropping canreduce per unit cost of production dramatically. As a result, research on breeding,cultural practices, and economics of ratooning is increasing.AREA AND CLIMATEThe approximately 200,000 ha planted to rice in Texas during peak production yearslies between 94 and 97 west longitude and between 28 and 30 north latitude, alongthe Texas-Louisiana Gulf Coast. Altitude varies from near sea level to 30 m above.Mean annual rainfall is 1,374 mm on the east edge, 889 mm on the west edge.Monthly rainfall (86-137 mm) is fairly evenly distributed through the year; Octoberand March have the lowest rainfall and May-September the highest. Soils, alluvialclay and sandy loams, remain wet through much of December-February whenrainfall/evaporation ratios range from 1.6 to 2.5. The ratio drops to about 1 duringthe summer.Because of less favorable light and temperature (below 10 °C) as winterapproaches and because hurricanes occur most frequently during August-September, rice producers obtain their best yields when they harvest the main cropbefore mid-August. When the main crop is not harvested by the end of August,ratoon cropping may not be economical because the ratoon crop is likely to beexposed during flowering to temperatures low enough to cause sterility. The averagedate of first frost is 28 Nov, the average date of last frost is 26 Feb. The normalgrowing season for rice is about 210 d.The growing season in other parts of the U. S. rice belt (Arkansas, California,and Mississippi) is too short for commercial ratoon crop production.PRODUCTION PRACTICESCultivar selectionEarly or very early maturity (100-130 d from seeding) is necessary for any cultivar toproduce consistent, satisfactory ratoon crop yields in the Southern U.S. For the pastdecade, Labelle has been the primary cultivar used for ratoon cropping. With therelease of Lemont and Skybonnet in 1983, hectarage planted to Labelle hasdecreased markedly.