A COMPARISON BETWEEN MCPA AND PESCO is-I5 FOR THE ...
A COMPARISON BETWEEN MCPA AND PESCO is-I5 FOR THE ...
A COMPARISON BETWEEN MCPA AND PESCO is-I5 FOR THE ...
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was apparently due to the periodic d<strong>is</strong>turbances<br />
in the plot at times of weeding, resulting<br />
from trampling and also possible mechanical<br />
damage to the crop during hoeing.<br />
Weed Control.- The relative effectiveness<br />
of different treatments on the control of weeds<br />
was also assessed by scoring at the same time<br />
as scoring was done for crop health. The<br />
following scale (Table 5), also a modification<br />
of one used by Green and Kaloger<strong>is</strong> (1963) in<br />
Arusha, was used.<br />
PeE <strong>MCPA</strong> 3 pts/ac 1<br />
PeE <strong>MCPA</strong> 5 pts/ac 2<br />
PeB Pesco 3 pts/ac 3<br />
PeE Pesco 5 pts/ac 4<br />
PoB <strong>MCPA</strong> 3 pts/ac 5<br />
PoE <strong>MCPA</strong> 5 pts/ac 6<br />
PoE Pesco 3 pts/ac 7<br />
PoE Pesco 5 pts/ac 8<br />
Hand Weeding 9<br />
No Weeding '10<br />
TABLE 6<br />
SCORES OF WEED DENSITY<br />
Weeding Control.-On the 4th of November,<br />
12 days after pre-emergence application<br />
weed growth in the treated plots were much<br />
less than in the untreated plots with the<br />
exception, of course, of the 'hand weeded'<br />
plots. On the 18th of November, 26 days<br />
after pre-emergence application the effect<br />
of the herbicide seemed to have waned<br />
.off a bit with the lower levels of pre-emergence<br />
application of either <strong>MCPA</strong> or<br />
Pesco 18-15, but control in the pre-emergence<br />
plots was still very much better than in<br />
the untreated plots, except the 'hand weeded'<br />
':p1ots'. At th<strong>is</strong> time the post-emergence<br />
application had not been given should be<br />
, oonsidered untreated.<br />
TABLE 5<br />
WEED DENSITY SCALE<br />
Score Reference<br />
5 No weeds<br />
4 Few weeds<br />
3 Moderate stand of weeds<br />
showing symptoms of suppression<br />
by herbicides<br />
2 Dense stand of healthy weeds<br />
1 Very dense stand of healthy<br />
weeds<br />
o Complete cover by weeds.<br />
Table 6 below gives the scores recorded on the<br />
three different dates for the various treatments.<br />
By the 11th of February, i.e. 92 days<br />
after pre-emgergence application, the effect<br />
of the herbicide applied pre-emergence<br />
seemed to have faded away completely.<br />
Th<strong>is</strong> was reflected in the predominance of<br />
weeds in these plots. The post-emergence<br />
application, which had been applied 41<br />
days before, showed a remarkably better<br />
control, compared with the pre~emergence<br />
application plots. .<br />
The life of a herbicide after its application<br />
in the field determines the duration of its<br />
effectiveness. Leaching and biological<br />
activities are the two main factors leading
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