Abstract: Three experiments were conducted in the field using common cocklebur as a test species to identify weed growth differences due to propagation method and weed age when transplanted (with no crop and with soybean). Two experiments involved weed establishment in noncrop areas using four propagation methods (direct seeded–transplanted, peat tablets, peat pots, and plastic inserts) in a factorial arrangement with three transplant timings (at the cotyledon stage, at two true leaves, and at four true leaves). A direct-seeded method was also included as a check. Propagation methods and transplant timings were contrasted to the direct-seeded method because it was the “most natural” method of those tested. Based on results from the first year, the peat tablet method at the three transplant timings plus the direct-seeded method were used to establish the weed in a field experiment with soybean. In 1996 at 4 wk after emergence (WAE), 8 WAE, and senescence, weeds planted in peat tablets and transplanted at the cotyledon stage were most similar to the direct-seeded method. Peat pots and plastic inserts displayed an intermediate number of differences, whereas direct-seeded–transplanted weeds exhibited the most differences of any propagation method. Transplanting at the two-leaf stage showed more differences, with the four-leaf stage showing even more. In 1997 at 4 WAE, few propagation methods or transplant timings were different from the direct-seeded method. Results from harvests at 8 WAE and at senescence were comparable to those in the previous year. Differences between years at 4 WAE were attributed to greater heat stress and less moisture early in 1996. When common cocklebur was grown in soybean, no differences were detected at 4 WAE between peat tablets transplanted at the cotyledon stage vs. direct-seeded weeds and only one difference when transplanted at the two- and four-leaf stages. At 8 WAE, the early transplant was again the most comparable treatment to direct-seeded weeds, with many differences at the later transplant timings. At senescence, weed differences were no longer apparent. Patterns established for peat tablets with the weed growing alone largely held true when it was grown with soybean.
Nomenclature: Common cocklebur, Xanthium strumarium L. #3 XANST; soybean, Glycine max (L.) Merr. ‘Manokin’.
Additional index words: Propagation methods, transplant timings, direct seeded, peat tablet, peat pot, plastic insert, weed ecology, competition, interference, XANST.
Abbreviations: POST, postemergence; WAE, weeks after emergence.