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Reflood Timing for Ratoon Rice Grown on Everglades Histosols

Dep. of Agronomy, H.J. Patterson Hall, Univ. of Maryland, College Park, MD 20742
Univ. of Florida, Everglades Res. and Education Ctr., PO. Box 8003, Belle Glade, FL 33430

^* Corresponding author

Rice (Oryza sativa L.) ratooning is commonly practiced in the Everglades Agricultural Area of southern Florida, yet optimum length of the drained period between main and ratoon crops has not been determined. Research was conducted to determine the effect of length of drain period at main-crop harvest on ratoon rice productivity on an Everglades Histosoi. Our research was conducted in 250-L (0.95 m height, 0.58 m i.d.) custom-made water control lysimeters filled with a Pahokee muck.soil (euic, hyperthermic Lithic Medisaprist). Ratoon reflood timing treatments were 0, 5, 15, 25, 35, and 45 d drained beginning at maincrop maturity. Ratoon-crop grain yield exhibited a significant quadratic response to length of drain period with maximum grain yield produced at 28 d drained. Ratoon panicle number was not affected by reflood timing, but quadratic responses to length of drain period were observed for grain number and 1000-grain weight. We propose that the resultant effect of rettood timing on ratoon grain yield was the combined responses to increasing mineral N supply and increasing water stress associated with delayed reltooding. For drained durations =28 d, the beneficial effects of increased mineral N supply resulting from organic matter oxidation resulted in a net increase in ratoon-crop yield. Conversely, for drained periods >28 d, the detrimental impact of prolonged water stress dominated the response to reflood timing and ratoon rice yields declined.

Received for publication June 14, 1993.