Jason Bond1, James P. Leonards2, and Ronald P. Regan2. (1) Louisiana State University AgCenter, 1373 Caffey Road, Rayne, LA 70578, (2) LSU Agcenter, 1373 Caffey Road, Rayne, LA 70578
Ratooning, the practice of harvesting grain from tillers originating from the stubble of a previously harvested crop (main crop), enhances rice grain yields without increasing land area because it provides higher resource use efficiency per unit of land area and per unit of time. Current Louisiana recommendations for rice ratoon production suggest application of nitrogen at 84 to 100 kg ha-1 immediately following main-crop harvest and establishment of the ratoon-crop flood immediately following nitrogen fertilization. An experiment was conducted from 2002 through 2004 at two locations in southern Louisiana to examine the response of four rice cultivars to ratoon nitrogen applications. Treatments were arranged as a factorial of rice cultivar and ratoon nitrogen application rate. The cultivars ‘Cypress', ‘Cocodrie', ‘CL161', and ‘Cheniere' were cultured using a delayed-flood, drill-seeded production system. Main-crop rice was harvested in late-July to early-August each year. Following main-crop harvest, nitrogen as urea was applied at rates of 34, 68, 100, or 134 kg ha-1. The number of days from main-crop harvest until 50% panicle emergence of the ratoon crop (50% heading) was not affected by nitrogen rate for Cypress, Cocodrie, and Cheniere. CL161 reached 50% heading 2 d earlier following application of 134 kg N ha-1 compared with 34 or 68 kg N ha-1. This is in contrast to observations with main-crop rice; however, growth and development of ratoon rice is not completely understood. Ratoon grain yields of all four cultivars increased with nitrogen rate up to 100 kg N ha-1. The production and harvest of a ratoon crop can potentially increase the productivity per acre in areas such as southern Louisiana where environmental conditions in late-summer and fall are often favorable for harvesting a ratoon crop. Current nitrogen recommendations are sufficient for ratoon rice production in Louisiana.
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