Degree Type


Date of Award


Degree Name

Doctor of Philosophy




The effects of seedbed tillage and row cultivation on established hemp dogbane (Apocynum cannabinum) and the establishment of perennial weed species were studied. Moldboard plow, chisel plow, tandem disk, and no tillage with and without subsequent row cultivations were compared on an established stand of hemp dogbane. Intensive seedbed tillage coupled with 1-2 row cultivations did not reduce hemp dogbane populations or root carbohydrate reserves compared to no tillage treatments after 3 years;Hemp dogbane root development and structure below the plow layer were not altered by seedbed tillage. Tillage effects on root development within the plow layer were discussed. Morphological development was affected by seedbed tillage, but these differences lessened and were nonexistent at the end of each season;Hemp dogbane root carbohydrate levels fluctuated, with seasonal lows occurring during flowering. Starch was the major carbohydrate storage form. Lipid levels did not show any appreciable trends. Hemp dogbane emergence did not appear strictly regulated by soil temperatures. Longer photoperiod daylengths enhanced intact crown root dormancy break in growth chamber studies;Hemp dogbane and American germander (Teucrium canadense) populations increased regardless of seedbed tillage practices used after five years of no tillage, till-plant, chisel plow, and moldboard plow systems in the perennial weed establishment study. Hemp dogbane and American germander populations increased at a faster rate, although not significantly, where no tillage and till-plant systems were used.



Digital Repository @ Iowa State University,

Copyright Owner

Roger Lee Becker



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123 pages