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Copyright 2005, Board of Trustees, University
Agronomy Research Report AG 73-4 March, 1973
CHEMICAL WEED CONTROL IN TOBACCO
New Agronomy Farm, 1972 /,
Fred Clark and Merrill Wilcox1
INTRODUCTION. Studies of chemical control of weeds iP 'f cured a were
continued in 1972 and the results are reported in this 'r/,A general dis-
cussion of the problems associated with chemical weed contCol, ~?Ltobacco was
presented in Agronomy Mimeo Report AG 68-8, January, 1968. 'Of -
MATERIALS AND METHODS. The soil type used was Jonesville-Hernando fin d,
containing approximately 2.2 percent organic matter. Fourteen chemical treat-
ments and one check, or untreated plot, were included, using three replications
for each treatment. Thirteen treatments were applied preplant on April 4, using
26 gallons of water per acre for each treatment. A calibrated hand sprayer
equipped with a pressure regulator in the discharge was used to spray the plots.
The treatments were incorporated to a depth of 2.5 inches within one hour after
application by means of a rototiller leaving a smooth soil surface. Hicks Broad-
leaf variety was planted April 5. Four postplant treatments were applied pn
April 6, immediately following transplanting, by spraying over the tops of the
plants.Three of these treatments were applied to plots which previously had
been treated preplant. Application rates are expressed in terms of the chemical
name listed in Table 1.
Each plot consisted of four rows spaced approximately 40 inches apart and
forty feet long. An application of 1000 lb 4-8-12 fertilizer per acre was made
before planting, and another of 150 lb of a 13-0-44 nitrate of potash side-
dressing per acre was applied two weeks later.
Weed control and plant vigor ratings were made of three replications inde-
pendently on May 18, and averaged. Vigor ratings are a linear estimate of aver-
age above-ground growth per plant, with 10 indicating normal growth. Crop stands
were not rated, as no differences were apparent. The weed control ratings are a
linear estimate of the average weed population in the plot. A rating of 10 re-
presents 100% control; G.0 of higher is considered commercially acceptable weed
control. All plots were plowed June 1. The tobacco was harvested June 20, and
July 6 and 21. After curing, the tobacco was weighed and sampled for grading
which was done by officials of the grading and market service of the U.S. Depart-
ment of Agriculture.
RESULTS AND DISCUSSION. All data are presented in Table 2. Yields were quite
satisfactory for most treatments.
1 Agronomist and Associate Professor, respectively, Gainesville.
The combination of R-7465 plus EI-179 plus pebulate resulted in the high-
est weight and dollar yields. R-7465 alone and other combination treatments
involving the same herbicides provided most of the better performances in the
Most of the treatments described here are not approved for use by growers
and require further evaluation. Growers should consult the Agricultural Exten-
sion Service for recommendations.
Chemicals Used in These Studies
To be released later.
Tobacco Weed Control, Newberry Road
Gainesville, Florida 1972
Weed Control Ratings2
Rate Time of Cyperus Eleusine Digitaria Richardia Galium per/A per Value
Herbicide Ib/A Application rotundus indica sanquinalis scabra aparine 100 wt $per/A
Preplant incorporated (i.e. PPI), treated April 4, 1972, incorporated to 2.5-inch depth in one hour. Planted with Hicks
Broadleaf variety April 5, 1972. Post-plant (i.e. POT), treated April 6, 1972 over the tops of the plants.
See text for explanation of ratings. Ratings taken on May 18, 1972.
: An average of only two replications was available because of variable weed stands.
'-*A rating of only one replication was available because of variable weed stands.
Tobacco fertilized with 1000 pounds of 4-8-12 per acre before transplanting and 200 pounds 13-0-44 top timer was applied
2 weeks later. Harvested June 20, July 6, and July 21.
The tobacco was cultivated June 1, 1972.-