Abstract
<p>A study on economic evaluation of some weed management strategies and herbicide residues analysis on roots of cassava (<em>Manihot esculenta</em> 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.</p>
Highlights
Cassava (Manihot esculenta Crantz) is grown nearly by every farming family in Ghana and it is used as animal feed, source of income, agro-industrial uses and accounts for a daily calories intake of 30% (Food and Agricultural Organization [FAO], 2006; Iyagba, 2010).Hand pulling, hand slashing and hoeing are the most widespread weed control methods used by subsistence farmers in Africa (Chikoye et al, 2002), but proved to be inefficient due to drudgery, time consuming, labour intensive and expensive (Vissoh et al, 2004; Ekeleme, 2013)
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
The higher yields observed in plots sprayed with Terbulor + 2 hoe weedings could be attributed to non-photoxic effect of the herbicide which led to better utilization of growth resources than other treatments
Summary
Hand slashing and hoeing are the most widespread weed control methods used by subsistence farmers in Africa (Chikoye et al, 2002), but proved to be inefficient due to drudgery, time consuming, labour intensive and expensive (Vissoh et al, 2004; Ekeleme, 2013). Herbicides are effective when applied to young and actively growing weeds, but less than 5% use of herbicides are adopted by smallholder farmers in Africa (Overfield et al, 2001; Udensi et al, 2012). Herbicide residues in crops are unavoidable even when applied correctly, serious concerns have been raised about health risks resulting from herbicide residues in food items by the environmentalists, consumers, producers, processors and marketers (Darko & Acquaah, 2007; Damalas & Eleftherohorinos, 2011)
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