Vol. 16—1962 - NorthEastern Weed Science Society

EFFECTOF HERBICIDESONQUALITYANDYIELDOF SWEETPOTATOES
(A PROGRESSREPORT)
William V. Welker. Jr.
1
Weeds are one of the maJC?3!' problems in the culture of sweet
potatoes. Four to six CUltivations per season plus hand weeding
are general practices employed in sweet potato culture. Chemical
weed control measures would appear to have considerable economic
potential. The project was initiated in 1959 with greenhouse
screeni~ 9f chemicals on fo~ varieties of18weet potatoes. The
most promi 13ing chemicals .\'fe~etaken to the field in 1960. Most
of the treatments were repeated during 1961.
The field experiments were carried out on a sandy loam soil.
A randomizedcomp~ete block design with fo~ replicates was used.
Each plot consisted of two rows 30 feet long with a guard row on
each side. All herbicides. exgept NPA (N-l-naphthylphthalamiC
acid) which was applied as a granular. were applied as sprays.
The sprays were applied over the foliage of the sweet potato
plants shortlY after the plants were set in the field. During
1960 the plots received normal cultivation between the rows beginriing
three weeks after the herbicides were lil,pplied. During .
1961 the plots,.received no CUltivation af'terthe herbicide treatments.
WeedsW:~re counted several times during each season.
All plots were hand-weeded at the normal ~ay-by time.
, '
The predominant weed species :r;>resent . both years were
crabgrass (D1~taria s uinal s (L.) Scap.)., pigweed (Amaranthus
retronexus r.. iambsquarters Cheno odium album L.). arid common
ragweed (Affibrosi •• edata taken included weed
control. inJury rattemiS11f',Olia
"01 owing herbicide application •. yie1d. internal
color analysis. organoleptic tests. and herbicide ef'fect on storage
and sp~ou.t1ng.
. The speCific effect of the herbicides ,upon yields weed control.
and quality factors will be discussed., Amiben b amino..... 2.
5·-dic~orobenzoic acid). casoron (2.4 dic~orobenzon1trile). diphenamid
(N.N-dimethyl-i,-7(-diphenylacetamide}. and dacthal
(dimethyl 2.3.5.6 tetrach10roterephalate) appeared acceptable with
respect to all factors studied. NPAwas not included in the 1961
experiment because of its harmful ef'fects upon skin quality found
in the 1960 experiments. CIPC (isopropyl N-(3-chlorophenyl)
carbamate) injured the sweet potato plant and reduced yield. The
weed control obtained with CIPC was less satisf'actory than that
obtained with the other compounds. Diphenamid was included only
in the 1961 experiments.
These studies indicated that the solution of the weed control
problem without a reduction of sweet potato yields is at hand.
Additional investigation of the effects of herbicides on quality
is needed.
91
lHorticulturist. Crop Research Division. AJzricultu:ral Rf'HIAA,.~h