Tuesday, November 6, 2007 - 11:15 AM
160-7

Improved Hybrid Rice Yield Using Increased Nitrogen Plus Growth Retardant.

Lee Tarpley, Texas Agricultural Experiment Station, Texas A&M Agricl. Res. & Ext. Ctr., 1509 Aggie Dr., Beaumont, TX 77713 and Timothy Walker, Mississippi State University, Delta Research & Ext. Center, PO Box 197, Stoneville, MS 38776.

The early-maturing rice (Oryza sativa L.) hybrids have the highest yield potential among cultivars for the mid-south US. Yet, studies conducted in Texas and Mississippi indicate their yield is limited by current nitrogen (N) fertilization rates. For example, in 2006 in Texas, the use of 225 kg/ha N to the main crop as a three-way split increased total (main and ratoon) crop yield by 1568 kg/ha (adjusted to 12% moisture) to 16,232 kg/ha compared to 160 kg/ha N to the main crop as a two-way split. However, adding additional nitrogen increases the risk of lodging. The use of a plant growth retardant (Palisade [Syngenta]) applied about 14 d after panicle differentiation was evaluated to decrease final plant height and the risk of lodging. In 2006, the additional use of the growth retardant resulted in yields that were 560 kg/ha less than those observed with the higher N rates alone, but still provided a net yield gain due to the combined treatments of 1000 kg/ha, which appears to be economically worthwhile for the producers. These studies were repeated in Texas and Mississippi in 2007. In addition, the use of a gibberellin treatment applied at soft dough of the main crop to increase ratoon crop yield was evaluated as part of the combination of treatments. In previous studies, the gibberellin treatment resulted in an average increase in ratoon crop yield of the hybrids of 670 kg/ha. The combination of higher nitrogen rates, plant growth retardant application two weeks after panicle differentiation, and a late-season gibberellin application has the potential to significantly increase the economic yield of hybrid rice production in the mid-south US.

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