Abstract

An on-farm experiment was conducted in Zanyokwe irrigation scheme to investigate the effects of row spacing (45 and 90 cm) and atrazine dosage (33, 67 and 100% of the label recommended dosage) on weed density and biomass and on maize yield. Overall percent kill of weeds increased with increase in atrazine dosage and with reduction in row spacing. Percent kill varied according to weed species with a 100% kill of broad leaf weeds such as Amaranthus hybridus,Nicandra physaloides and Bidens pilosa regardless of herbicide dosage whileDigitaria sanguinalis, Cyperus esculentus, Cynodon dactylon and Oxalis latifoliacould not be controlled even at the LRD. Weed density at maize physiological maturity decreased by 11% when row spacing was decreased from 90 to 45 cm. Atrazine dosage and row spacing did not have significant interactive effects and their main effects did not significantly affect weight of green cobs, cob length or grain yield. The study demonstrated the possibility of incorporation of reduced herbicide dosages and narrow rows to achieve adequate weed control and optimise on yields in smallholder farming systems.

Key words: Row spacing, reduced atrazine dosages, weed density, weed biomass, maize yield.

Abbreviation

Abbreviations: RHDs, Reduced herbicide dosages; LRDs, label recommended dosages; WAE, weeks after emergence; a.i, active ingredient; ZIS, Zanyokwe irrigation scheme; SA, South Africa.