Masters Thesis
Field experiments were conducted at Kilombero Sugar Company estate one under rainfed
and another under rainfed plus supplemental irrigation condition to evaluate the effects of
herbicides on weeds and sugarcane (Saccharum officinarum L) yield and quality.
Experiments were laid out in a randomized complete block design with four replications.
Plot sizes of 5.8 m x 4 m were used. Treatments were Volmazone (2-(2-chlorobenzyl)-4,4-
dimethyl-1,2-oxazolidin-3-one) at 2.9 and 3.8 kg a.i ha-1; Acetochlor 2-chloro-Nethoxymethyl-
6-ethylaceto –o-toluidide at 4.5 and 6.0 kg a.i ha-1 and Metribuzin 4-amino-
6(1,1-dimethyl)-3-Methilthio-1,2,4 triazin-5(4H) 6.0 and 7.5 kg a.i.ha-1. Which were
applied as early post emergence. These were compared with weed free check which was
hand weeded every two weeks and untreated check. Results revealed that there was
significant difference between herbicides treated plots as compared to unweeded check
plots (p < 0.05). There was no significant difference between herbicide treated plots and
weed free check. All herbicides were effective in controlling grasses and broadleaf weeds
to an acceptable level above (90%) up to 8 WAT for both irrigated and rainfed crop, a
period which is quite satisfactory for sugarcane. There were variable herbicide treatment
effects on individual grass weed species. Itchgrass was best controlled by Volmazone,
while Leptochloa and Echnochloa spp were best controlled by acetochlor and metribuzin.
Almost all herbicide treatments were ineffective incontrolling nut sedges the control was
bellow an acceptable level 90%, although were significant (p < 0.05) as compared to
unweeded check. There was a significant difference in sugarcane yield tons ha-1 between
herbicides treated plots as compared to unweeded check plots (p < 0.05) for both irrigated
and rainfed experiments,but no significant difference in sugarcane yield was observed
between herbicide treated plots and weed free check (p < 0.05). For the irrigated
experiment, the treatment with acetochlor 4.5 kg a.i ha-1increased yield by 74.7 % which
was higher than all other treatments. Other treatments, volmazone 3.8 kg a.i ha-1;
metribuzin 6.0 kg a.i ha-1;volmazone2.9 kg a.i ha-1; metribuzin 7.5 kg a.i ha-1; weed free
check and acetochlor 6.0 kg a.i ha-1 increased yield between 37.8 and 57.3 % compared to
unweeded check. For the rainfed experiment, treatment with acetochlor 4.5 kg a.i ha-
1increased yield by 50.0 % and other treatments that is acetochlor 6.0 kg a.i ha-1;
metribuzin 6.0 kg a.i ha-1; weed free check; metribuzin 7.5 kg a.i ha-1; volmazone 3.8 kg a.i
ha-1 and volmazone 2.9 kg a.i ha-1 increased the yield of sugarcane between 40.3 and 48.8
% over unweeded check. Both irrigated and rainfed experiments sugarcane yields tons ha-1
positively correlated with number of millable stalks population (r = 0.834 and 0.942)
respectively. Different treatments of herbicides had no effect on sugarcane quality
parameters (P < 0.05). Economic analysis showed that the highest net benefit and marginal
rate of return of 1124.2% was achieved by treatment with volmazone at 2.9 kg ai ha-1for
irrigated experiment and for the rainfed experiment the highest net benefit and marginal
rate of return of 412.3 % was achieved by treatment with acetochlor at a rate of 4.5 kg a.i
ha-1.
COSTECH