MSc

Elephant foot yam (Amorphophallus paeoniifolius (Dennst.) Nicolson) is a
popular tropical tuber crop grown in Kerala because of high production potential and
net returns. In Kerala, elephant foot yam is second in importance as a tuber crop after
cassava and in 2015 - 16, it was grown in 7143 ha. In general, weed competition is an
important constraint in the production of tuber crops owing to their initial slow
growth. Elephant foot yam, being a widely spaced crop, takes 50 - 60 days or more to
spread into full ground cover. Therefore, in the early growth stage of this crop,
enough sunlight and space are available for weeds to flourish. Manual weeding is the
most common method of weed control practiced in elephant foot yam, and two
weedings, one at 45 days and the second at 75 days followed by earthing up, are
recommended in Kerala. However, the high cost of manual weeding and non-
availability of labour are major constraints in weed management, and so, farmers seek
alternate methods of weed control.
The present experiment entitled “Weed management in elephant foot yam
[Amorphophallus paeoniifolius (Dennst.) Nicolson]” was conducted
in the
Department of Agronomy, College of Horticulture, Vellanikkara during March to
December 2016 to study the effect of frequency of weeding and various weed
management techniques on the growth and yield of elephant foot yam. Treatments
included manual weeding (twice, thrice, and four times), weed management by
herbicides, mulching with black polythene sheet, mulching with dry grasses,
intercropping with cowpea, and unweeded control.
Among various treatments, mulching with black polythene displayed superior
biometric characters and yield. Mulching with black polythene showed the highest
per plant leaf area of 83.11 dm2 and leaf area index of 1.02. The treatments with
herbicides were next in order. All the plots receiving manual weeding were on parwith respect to leaf area and LAI. Irrespective of the stage of crop, mulching with
black polythene produced higher plant dry weight throughout the crop period. The
treatments, mulching with dry grasses and intercropping with cowpea were not
effective in suppressing weeds to any marked level as shown by lesser crop dry
weight throughout the growth period.
Mulching with black polythene greatly influenced the height, diameter, and
volume of corm followed by pre emergence application of oxyfluorfen and directed
spray of glyphosate. Mulching with black polythene also positively influenced the
fresh weight of corm, recording the highest fresh weight of 2.70 kg/ plant and corm
yield of 35.77 Mg/ha, which was 63 per cent higher than unweeded control. Increase
in frequency of manual weeding also caused significant effects on fr esh weight of
corm and corm yield per hectare. Mulching with dry grasses, intercropping with
cowpea, and pre emergence application of pendimethalin were not very effective in
obtaining higher corm yields.
Mulching with black polythene was the best option to manage weeds in
elephant foot yam fields at all growth stages. In general, application of herbicides
limits the weed dry weight greatly but pre emergence application of pendimethalin
was not that effective compared to oxyfluorfen and glyphosate. Mulching with black
polythene maintained the highest weed control efficiency at all the stages except at
165 DAP. However, mulching with black polythene gave consistent weed control
efficiency upto 105 DAP after manual weeding four times, and at 165 DAP, it was
the second best in controlling weeds.
An increase in soil acidity and organic carbon content was observed after the
harvest of crop. In general, mulching with black polythene recorded higher contents
of all nutrients except N in soil. Mulching with black polythene resulted in higher
nutrient contents in corms both at 90 DAP and harvest. Uptake of major nutrients was
also higher in this treatment. Among manually weeded plots, weeding thrice and four
times resulted in on par uptake of N and P at harvest. Directed spray of glyphosate
and pre emergence application of oxyfluorfen resulted in higher nutrient uptake
among the plots receiving herbicidal application.
The highest benefit - cost ratio of 2.33 was recorded with mulching with black
polythene. The B : C ratio of pre emergence application of oxyfluorfen and post
emergence spray of glyphosate were 2.28 and 2.24 respectively. Manual weeding
four times resulted in a B : C ratio of 2.02. From this experiment, it can be concluded
that mulching with black polythene, pre emergence application of oxyfluorfen and
post emergence application of glyphosate can be effectively utilized for weed
management in elephant foot yam.