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Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only Publication Acceptance Date: 1/27/2005 Publication Date: 5/15/2005 Citation: Johnson, W. C. 2005. Starting from scratch: Growing peanut without herbicides [abstract]. Proceedings of the Weed Science Society. 58:92. Interpretive Summary: Technical Abstract: There is interest among peanut growers and industry in organic peanut production in the southeastern U. S. This interest is based on increasing consumer demand for organic foods, particularly organic peanut butter. Until recently, runner-type peanut cultivars had little host plant resistance to diseases. However, peanut cultivars 'DP-1' and 'C11-2-39' have been recently released and both cultivars have excellent resistance to many peanut diseases. With effective disease management possible using resistant cultivars, the next major challenge in organic peanut production is weed management. Trials were conducted in 2003 at the Coastal Plain Experiment Station in Tifton, GA in conventional tillage and strip-tillage production systems. The conventional tillage trial evaluated two levels of stale seedbed management, two row patterns, and five levels of weed control using propane flaming. The strip-tillage trial was conducted at a site with a senescent rye cover crop. This trial evaluated all combinations of three levels of cover crop management and nine levels of weed control using propane flaming. Both trials were conducted at sites managed for weed science research with heavy natural populations of southern crabgrass, pitted morningglory, and yellow nutsedge. In the conventional tillage trial, shallow tillage of stale seedbeds twice before planting provided better early season weed control compared to stale seedbeds flamed three times before planting. Early season ratings showed weed control was not improved by narrow row patterns over wide row patterns. Over-the-top propane flaming sequentially at peanut emergence and one week after emergence provided early season weed control nearly comparable to the standard herbicide check, when used in conjunction with shallow tillage of stale seedbeds. Peanut exhibited acceptable tolerance to over-the-top propane flaming early season. Despite the promising efficacy of multiple propane flamings for weed control, the lack of residual weed control was evident later in the season and trials were not harvested due to heavy weed infestations. In conservation tillage trials, burning, mowing, or planting directly into standing rye resulted in numerous weed escapes that could not be controlled by propane flaming after planting. Trials were reconfigured in 2004 and were conducted using conventional tillage production practices. In one trial, weed management systems were evaluated using a factorial arrangement of row patterns (wide rows and narrow rows), OMRI-approved herbicides (Matran, Ground Force, and propane flaming), and sweep cultivation (cultivated two times and four times). Weed management was not improved by narrow row patterns over wide rows due difficulties in cultivating narrow row patterns. Matran and propane flaming controlled initial flushes of dicot weeds, but did not effectively control annual grasses. Ground Force did not effectively control any of the weeds present in these trials. Neither Matran, Ground Force, nor propane flaming provided residual control of weeds and subsequent weed emergence resulted in severe weed infestations by mid-season. Cultivation had the greatest effect of all treatments. However, there were fewer cultivations when peanut were seeded in narrow row patterns compared to wide rows. In subsequent weed free trials, peanut tolerated single applications of Matran and Ground Force, when applied no later than two weeks after emergence. Multiple applications or single applications of Matran later than two weeks after emergence injured peanut and reduced yield. These trials clearly show the extreme difficulty in managing weeds in organic peanut production. Matran and propane flaming control small dicot weeds, but not annual grasses. Furthermore, none provide residual weed control. Sequential applications are costly an |
