Affiliation(s)
1. Department of Agriculture, School of Agriculture and Bio-Sciences, Karunya Institute of Technology and Sciences (Deemed University), Karunya Nagar, Coimbatore 641 114, Tamil Nadu, India
2. Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, India
ABSTRACT
Crops made resistant to herbicides
by biotechnology are being widely adopted in various parts of the world and several
herbicide resistant crops have become available in many countries for commercial
cultivation. But in India, the technology of herbicide tolerant crops is in initial
stage of field evaluation. Hence, field trials have been carried out to evaluate and consolidate
the agronomic advantages of herbicide tolerant transgenic cotton and maize. Herbicide
tolerant stacked traits of maize and cotton have been evaluated under Bio-safety
Research Level (BRL I) as confined field trials for its agronomic efficiency on
weed control and enhanced crop productivity at Tamil Nadu Agricultural
University (TNAU), Coimbatore and Punjab
Agricultural University (PAU), Ldhiana for many years. In both crops, potassium salt formulation
of glyphosate was sprayed at different doses (900, 1,350, 1,800, 2,700, 3,600 and 5,400 g a.e./ha twice at 25 days after sowing
(DAS) and 60 DAS in cotton and
900, 1,800 and 3,600 g a.e./ha at 25 DAS
in maize). Evaluation was made on weed control efficiency, phyto-toxicity on crops,
yield and economics and carry over effects on the succeeding crops. Application of glyphosate
at 2,700 g a.e./ha recorded
lower weed density, dry weight and higher weed control efficiency (WCE) in cotton. Post-emergence (POE) glyphosate at 900,
1,800 and 3,600 g a.e./ha registered lower weed
density, dry weight and higher WCE in transgenic Hishell and 900 M Gold and in 30V92
and 30B11 corn hybrids. Post-emergence application of glyphosate in transgenic maize
hybrids did not affect the germination percent, vigour and yield of succeeding green
gram in the transgenic maize trials and sunflower, soybean and pearl millet in cotton
trials. Phytotoxicity symptoms were not observed in cotton with glyphosate at lower
doses viz., 900, 1,350,
1,800 and 2,700 g a.e./ha. Higher doses viz.
3,600 g a.e./ha and 5,400 g a.e./ha were noticed with
phytotoxicity symptoms at early stages of herbicide application. Glyphosate applied
at 900, 1,350, 1,800 and 2,700 g a.e./ha recorded more number
of bacteria, fungi and actinomycetes compared to atrazine treatments. Higher grain
yield was recorded with POE application of glyphosate at 900, 1,800 and 3,600 g a.e./ha in Hishell and 900
M Gold transgenic hybrids and higher net return and benefit cost ratio were recorded in glyphosate
at 1,800 g a.e./ha in transgenic 900
M Gold in all the four seasons. Post-emergence application of glyphosate at 900 g a.e./ha and 1,800 g a.e./ha registered higher
grain yield in transgenic 30V92 and 30B11 corn hybrids. In maize and cotton transgenic
crops, post-emergence weed management
with glyphosate proved to be the better management option for the control of weeds.
KEYWORDS
Herbicide tolerant crops, weed control
efficiency, phytotoxicity, carry over effect, corn and cotton, productivity and
profitability.
Cite this paper
References