Submitted to: Weed Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/9/2006
Publication Date: 9/21/2006
Citation: Williams, M. 2006. Planting date influences critical period of weed control in sweet corn. Weed Science. 54:928-933. Interpretive Summary: The critical period for weed control (CPWC) identifies the phase of the crop growth cycle when weed interference results in unacceptable yield losses. The period in which crop planting occurs can span several months, especially for vegetable crops grown in the U.S. Planting date has potential to influence CPWC, because weed community composition and environmental conditions regulating plant growth change over time. Field studies in sweet corn demonstrated the significance planting date has on CPWC. Two planting dates separated by six weeks revealed a crop highly susceptible to weed interference when planted early, relative to a late planting date with considerable crop tolerance. This research is likely to impact weed management in corn production, especially sweet corn, by facilitating the use of crop-weed ecology information to optimize weed management systems.
Technical Abstract: The critical period for weed control (CPWC) identifies the phase of the crop growth cycle when weed interference results in unacceptable yield losses; however, the effect of planting date on CPWC is poorly known. Field studies were conducted in 2004 and 2005 at Urbana, IL to determine CPWC in sweet corn for early-May (EARLY) and late-June (LATE) planting dates. A quantitative series of treatments of both increasing duration of interference and length of weed-free period were imposed within each planting date main plot. The beginning and end of the CPWC, based on 5% loss of marketable ear mass, was determined by fitting logistic and Gompertz equations to relative yield data representing increasing duration of weed interference and weed-free periods, respectively. Weed interference stressed the crop more quickly and to a greater extent EARLY, relative to LATE. At a 5% yield loss level, duration of weed interference for 160 and 662 growing degree days (GDD) from crop emergence marked the beginning of the CPWC for EARLY and LATE, respectively. When maintained weed-free for 320 and 134 GDD, weeds emerging later caused yield losses of less than 5% for EARLY and LATE, respectively. Predominant weed species included barnyardgrass, common lambsquarters, common purslane, redroot pigweed, and velvetleaf. Despite weed densities exceeding 85 plants m-2 for the duration of the experiments, weed canopy height and total aboveground weed biomass were 300% and 500% higher, respectively, for EARLY compared to LATE. Interactions between planting date and CPWC indicate the need to consider planting date in the optimization of integrated weed management systems for sweet corn.