Phytotoxicity and mode of application of crude cassava water extract as a natural herbicide on weeds of cowpea

Abstract

Two field trials were conducted in 2007 and 2008 to evaluate the toxicity and mode of action of Crude Cassava Water Extract (CCWE)as a natural post-emergence herbicide on cowpea respectively with significant differences (p0.05).all herbicidal treatments  showed statistical differences(p<0.05) in cowpea plant height(CPH)and leaf area(LA).the highhest CPH and LA were recorded from handweeded,bulk and MS at 100% on F+SD in the trials.the yield parameters revealed all herbicide treatment achieved similar high values with statistical differences(p0.05)The cowpea grain yield recorded in 2007 and 2008 from CCWE were MS (520-600kg/ha^-1)and bulk (520-590kg/ha^-1)at 50 and 100% on F and F+SD which compared favourably with handweeded (530-600kg/ha^-1)while TMS was (360-470kg/ha^-1).although,TMS CCWE could not compared favourably with MS and bulk in most parameters,but it was significantly higher than weedy check.significantly reduced growth andd yield parameterrs with weeds.The study was a factorial trial laid out in split plot design with three replications.the main plot comprised of mode of application:foliage spray (F),soil drench(SD) and foliage +soil drench(F+SD),sub and sub plots were:CCWE herbicide of Bulk source,MS(Manihot selection),TMS(Tropical Manihot Selection) while weedy check and handweeded served as controls.the results showed contact and systemic action as the phytotoxicity of CCWE.the phytotoxic effects from bulk and MS at 100% on F and F+SD recorded over 50% on weeds of cowpea.about 77% and 82% for bulk and MS on F and F+SD reached herbicidal efficacies of weed biomass and density cowpea grain yield of 160-200kg/ha^-1 were recorded from weedy check in the trials.it is concluded that ,hydrogen cyanide(HCN) from CCWE is a causative factorr in the herbicidal actions in different mode of application which produced contact and systemic mode of action on weeds of cowpea.