The allelopathic influence of sweet potato cultivar 'Regal' on purple
nutsedge was compared to the influence on yellow nutsedge under contro
lled conditions. Purple nutsedge shoot dry weight, total shoot length
and tuber numbers were significantly lower than the controls (47, 36,
and 19% inhibition, respectively). The influence on the same parameter
s for yellow nutsedge (35, 21, and 43% inhibition, respectively) were
not significantly different from purple nutsedge. Sweet potato shoot d
ry weight was inhibited by purple and yellow nutsedge by 42% and 45%,
respectively, The major allelopathic substance from 'Regal' root perid
erm tissue was isolated and tested in vitro on the two sedges, The I-5
0's for shoot growth, root number, and root length were 118, 62, and 4
4 mu g/ml, respectively, for yellow nutsedge, The I-50's for root numb
er and root length were 91 and 85 mu g/ml, respectively, for purple nu
tsedge and the I-50 for shoot growth could not be calculated, Nomencla
ture: Purple nutsedge, Cyperus rotundus L. #(3) CYPRO, yellow nutsedge
, Cyperus esculentus L. # CYPES, sweet potato, Ipomoea batatas (Lam.),
'Regal.'