Economic Evaluation of Weed Control and Herbicide Residues on Cassava (Manihot esculenta Crantz) in Ghana

A study on economic evaluation of some weed management strategies and herbicide residues analysis on roots of cassava (Manihot esculenta Crantz) was conducted during 2014 and 2015 cropping season in Kumasi, Ghana. Cost and benefits were computed from the use of two manual weedings (hoeing and cutlassing), two pre-emergence herbicides (Butachlor 60% EC and Terbulor 500 EC) with two-supplemenatary hoe weeding, weed-free and weedy check. These were evaluated using two varieties of cassava, Ampong (Early branching) and Dokuduade (Late branching). The treatment was a factorial laid out in a randomized complete block design (RCBD) with four replicates. Partial farm budgeting were used for economic analysis of data and herbicide residues analysis in roots of cassava were determined using Gas Chromatography-Electron Capture Detector (GC-ECD). Results showed that Terbulor 500 EC with two supplementary hoe weeding was more economical, profitable and beneficial than those other treatments applied in the production of cassava. In addition, the average concentration of Terbulor 500 EC (0.003 mg/kg) and Butachlor 60% EC (0.001 mg/kg) residues in roots of cassava varieties were below the maximum residue limit (MRL) of 0.01 mg/kg set by Ghana Standards Authority for cassava. In conclusion, Terbulor 500 EC with two supplementary hoe weeding was more effective and financially rewarding and both herbicides had lower residual effects on cassava.