Evaluation of First Crop Cutting Height on Ratoon Crop Yield and Panicle Origin in Drill-Seeded Rice.

The climate in the Gulf Coast region of southwest Louisiana is conducive for growing a second rice crop from stubble left behind after the first crop harvest.  Manipulating rice stubble of the first crop by various methods, such as lowering the cutting height at harvest, rolling, or flail mowing after harvest, have been experimented with by producers with mixed results.  The objectives of the study were two-fold: 1) determine if harvesting at a lower height can provide a consistent ratoon yield advantage over normal harvesting practices and 2) evaluate origin and density of ratoon panicle development when the first crop is harvested at differing heights.  The 2-year study was initiated in 2006 at the LSU AgCenter’s Rice Research Station South Farm located just south of Crowley, Louisiana.  Treatments included two cultivars (‘Trenasse’ and ‘Cocodrie’) and two harvest heights (20 and 40 cm).  Ratoon rice panicles were tagged after emergence each week beginning 3 weeks after first crop harvest (WAH) and concluding 10 WAH.  Data obtained from the study included plant height, grain yield, panicle density, panicle weight, and panicle origin from 3 to 10 WAH.  Significant panicle emergence was not noted until 3 to 4 WAH during both years.  Total grain yields were significantly greater when the first crop was harvested at the lower cutting height for Trenasse in 2006 and both varieties in 2007.  The 20-cm harvest height delayed panicle emergence by 1 and 2 weeks in 2006 for Trenasse and Cocodrie, respectively.  Cocodrie panicles from the 40-cm harvest height treatment originated from upper nodes during 4 and 5 WAH, were equivalent with those originating from base nodes at 6 WAH and the majority originated from lower nodes at 6 WAH and beyond.  Average panicle weight was greater for those originating from base nodes compared with upper nodes.