MSc

Field experiments were conducted during summer and kharif
seasons of 1998 and 1999 at College of Horticulture, Kerala Agricultural
University, Thrissur, with the objective of developing an integrated method for
management of weeds, especially perennial weeds like Cynodon dactylon (L.) and
Cyperus rotundus L. in okra. Broadspectrum herbicide glyphosate, solarization,
smother croppmg with cowpea and monthly digging were compared with
unweeded control in the summer season, for their effect on weeds. In the
subsequent okra crop, during kharif season, different pre-emergence herbicides and
farmer's practice of hand weeding were compared with black polyethylene
mulching and unweeded control. The experiment was carried out in a split-plot
design with three replications, taking summer season treatments as main plots and
weed control methods in okra, as sub plots.
Cynodon dactylon and Cyperus rotundus were the predominant
perennial weeds in the field. Cyperus iria, Digitaria ciliaris, Dactyloctenium
aegyptium, Eleusine indica and Ludwigia parviflora were the major annual weeds.
In summer season.,) treatments solarization and glyphosate l.2 kg ha-1
were very effective in reducing the weed problems. They also resulted in reduction
in the underground vegetative propagules of perennial weeds. Solarization resulted
in increasing the soil temperature by 8.5 and 6. 7°C at 5 and 1 0 cm depths
respectively, during April.
In the subsequent okra crop, black polyethylene mulching gave
complete prevention of any weed problems. Among the other combinations,
glyphosate 1.2 kg ha" (twice at 45 days interval) during summer season followed
by metolachlor l.0 kg ha-1 + HW at 45 DAS in okra crop (in 1998) as well as
solarization followed by pendimethalin l.0 kg ha-1 + HW at 45 DAS (in 1999).

The total returns was higher ill plots which received polyethylene
mulching in the okra crop, irrespective of main plot treatments given in the
summer season. Among them, highest total return was obtained from glyphosate
1.2 kg ha-I in the summer season followed by polyethylene mulching in okra crop
(Rs.31,704 ha"), followed by solarization followed by black polyethylene
mulching (Rs.30,594 ha"). However, the highest return per rupee invested on weed
control was obtained from combinations of metolachlor 1.0 kg ha" (in okra) with
glyphosate 1.2 kg ha" in summer season (Rs.2.41), solarization (Rs.2.28) and that
of glyphosate 0.8 kg ha'. But all the combinations of weedy control in summer
season, except that of polyethylene mulching resulted in loss as far as the cost of
weed control and the total cost is concerned.