Abstract
AbstractWeed competition severely constrains cassava root yield in sub-Saharan Africa; thus, good weed control measures, including the use of herbicides, are increasingly important. Herbicide trials were conducted at five locations across eastern, western, and north-central Nigeria over two cropping seasons (2014 and 2015). Nineteen premixed PRE herbicides applied at different rates were evaluated for efficacy on weeds and selectivity on cassava. Manual hoe-weeding at 4, 8, and 12 wk after planting (WAP) and two S-metolachlor + atrazine treatments commonly used by cassava growers were included for comparison. Six of the 19 PRE herbicide treatments (indaziflam + isoxaflutole, indaziflam + metribuzin, flumioxazin + pyroxasulfone, isoxaflutole, acetochlor + atrazine + terbuthylazine, and terbuthylazine + S-metolachlor) consistently provided 80% to 98% broadleaf and grass weed control up to 8 wk after treatment. Overall, PRE herbicide treatments and cassava yield were significantly positively correlated. Herbicide treatments terbuthylazine + S-metolachlor, flumioxazin + pyroxasulfone, diflufenican + flufenacet + flurtamone (respectively, 60 + 60 + 60, 120 + 120 + 120, 90 + 360 + 120, and 135 + 360 + 180 g ha−1), acetochlor + atrazine + terbuthylazine (875 + 875 + 875 g ha−1), S-metolachlor + atrazine (870 + 1,110 g ha−1), oxyfluorfen (240 g ha−1), indaziflam + isoxaflutole (75 + 225 g ha−1), indaziflam + metribuzin (75 + 960 g ha−1), and aclonifen + isoxaflutole (500 + 75 g ha−1) contributed to yields exceeding twice the Nigerian national average of 8.76 tonnes ha−1. These treatments had root yields of 1.4 to 2 times higher than plots that had been hoe-weeded three times. There were some adverse herbicide treatment effects such as delayed cassava sprouting and temporary leaf bleaching observed in indaziflam and diflufenican + flufenacet + flurtamone treatments, whereas sulfentrazone caused prolonged leaf crinkling. The PRE applications alone at rates safe for cassava did not provide adequate season-long weed control; supplemental POST weed control is needed about 10 WAP for satisfactory season-long control.
Highlights
Cassava is extensively cultivated in the humid and subhumid tropical regions of Africa (Lebot 2009), which produces more than 54% of the world's cassava output (FAOSTAT 2014)
Nigeria is a global leader in cassava production with an output of approximately 59.5 million tonnes from 6.79 million hectares under cassava cultivation (FAOSTAT 2017)
Nineteen PRE herbicides (Table 2) and manual hoe-weeding at 4, 8, and 12 wk after planting (WAP) were evaluated for weed control efficacy
Summary
Cassava is extensively cultivated in the humid and subhumid tropical regions of Africa (Lebot 2009), which produces more than 54% of the world's cassava output (FAOSTAT 2014). Cassava plays a vital role in the food economy of many African countries, including Nigeria, where it remains a strategic crop for both food security and poverty alleviation (Donkor et al 2017; FAO 2011). This crop is an essential source of industrial raw material for the production of starch, bioethanol, high-quality flour for pharmaceuticals, food, and beverages and has the potential to contribute to the economic growth of Nigeria and most cassava-producing countries in sub-Saharan Africa
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