Congress grass possess herbicidal potential against weeds in wheat fields

An understanding about occurrence of weed species and patterns of change in incidence is dynamic in emerging weed managing approaches and give directions to future study endeavors. To appraise this threat, we studied the allelopathic effect of aqueous extracts of different parts of invasive weed congress grass, Parthenium (Parthenium hysterophorus L.) to biologically minimized weed risk in Wheat in 2012-13. Aqueous extracts of different plant parts (root, shoot, leaf, fruit and entire plant) of Parthenium were applied for three times as pre-emergence, post emergence and pre + post emergence. No significant grain yield differences were noticed between leaf extract and whole plant extract. Maximum weed density reduction (85.50%), weed dry biomass reduction (77.21%), weed control efficiency (85.67%), plant height (91.44 cm), biological yield (13426 kg ha-1) and grain yield (4437 kg ha-1) were found where leaf extract was applied as pre emergence spray. Whole plant extract sprayed as twice i.e. once as pre emergence and secondly as post emergence also gave better results showing weed density reduction (79.93%), weed dry biomass reduction (73.77%), weed control efficiency (80.09% ), biological yield (12253 kg ha-1) and grain yield (4414 kg ha-1). On other hand 11.08% decrease in grain yield occurred where fruit extract was applied as post emergence spray. Therefore for better wheat grain yield and reduced weed risk farmers can use spray of leaf extract of parthenium before weed emergence.