Vol. 51—1997 - NorthEastern Weed Science Society

107
REDUCED HERBICIDE RATES FOR
NARROW-ROW FIELD CORN
R. R. Hahn and P. J. Stachowski'
ABSTRACT
Thee fi ld experiments were conducted near Aurora, NY in 1996 to compare
effectiveness of educed herbicide rates as influenced by plant population and row spacing in
silage com (Zea mays L.). A split-split plot design with 15- or 30-inch rows as main plots and
populations of 3 ,000 and 45,000 plants!A as subplots was used. Sub-subplots were of full, twothirds,
and one- .rd rates of a standard treatment and an untreated check. A preemergence
(PRE) combina on of 1.5 lb ailA of pendimethalin plus 1.5 lb ailA of atrazine was used as the
standard for an xperiment with annual weeds including velvetleaf (Abutilon theophrasti
Medicus). The ther experiments investigated yellow nutsedge tCyperus esculentus L.) and
annual weed co trol. A preplant-incorporated (PPI) treatment of2lb ailA ofmetoclahlor plus
1.5 lbl A of a ne 'wasused as the standard for one of these experiments. An early
postemergence PO) standard of 0.75 oz ailA ofhalosulfuron plus l Ib/A ofatrazine with 1%
(v/v) of a petrol urn-based crop-oil concentrate was used for the other.
Row sp ing and plant population had no influence on weed control ratings except in the
EPO experimen where green foxtail [Setariaviridis (L.) Beauv.] control was better with IS-inch
rows than with O-inchrows. When pendimethalin and atrazine were applied PRE, common
ragweed (Ambr sia artemisiifolia L.) and velvetleaf control ranged from 91 and 78%
respectively wi one-third the standard rate up to 100 and 98% respectively with the full rate.
The full rate pr ided better velvetleaf control than the reduced rates and there was a difference
between the tw thirds and one-third rates. Although silage yields ranged from 30.7 T/A for the
untreated check p to 33.2 T/A, there were no significant differences among the treatments.
lied PPI, the one-third and full rates of metolalchlor plus atrazine controlled 71
and 89% of the utsedge respectively. There were differences in nutsedge control between the
full rate and the duced rates and also between the reduced rates. The full rate controlled 99, 97,
and 94% of the een foxtail, ladysthurnb (Polygonum persicaria L.), and common ragweed
respectively. ese ratings were not different from those with the two-thirds rate but were higher
than the 92, 81, d 78% control ratings with the one-third rate respectively. While there were
no differences i silage yield among the herbicide treatments, their average yield of 28.3 T/A was
higher than the 1.5 T/A from the untreated check. In the EPO experiment, nutsedge control
ranged from '74 0 90% for the three halosulfuron plus atrazine treatments and each was different
from the others. The average silage yield of28.0 T/A from the herbicide treatments was
significantly hi er thanthe 20.3 T/A from the untreated check.
'Assoc. Prof. Res. Supp. Spec., Dept. of Soil, Crop and Atmospheric ScL, Cornell Univ.,
Ithaca, NY 148 3.