Critical period for weed control in potatoes in the Huambo province (Angola)

• Autor(a) principal: Monteiro, Ana
• Data de Publicação: 2011
• Outros Autores: Henriques, I., Moreira, I.
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.5/5048
• topic: Solanum tuberosum; batata; tropical Africa; yield loss

ABSTRACT - The effects of different weed management periods on potatoes were studied in three areas (Bailundo, Chianga and Calenga) of the central highlands of Angola and in three cropping seasons, from June 2005 to May 2007. Six weed-management treatments were used to identify critical periods of competition and to allow the development of more precise management recommendations. Total potato yield ranged from about 22 tha-1 in weed-free plots to about 3 t ha-1 with no weed control – a yield loss of 86%. Major weed species – Galinsoga parviflora, Cyperus esculentus, Bidens biternata, Amaranthus hybridus, Nicandra physaloides, Portulaca oleracea and Datura stramonium – differed from area to area. The species G. parviflora dominated the weed flora in all three areas – 73, 97 and 72 plants m-2 50 days after crop emergence in Bailundo, Chianga and Calenga respectively, in dry season trials; while C. esculentus was also present in Chianga and Calenga, with an average density of ca 30 plants m-2 in dry season trials. Gompertz and logistic equations were fitted to data representing increasing periods of weed-free growth and weed interference, respectively. Critical periods for weed control, with a 95% weed-free total yield, were estimated from 26 to 66 and from 20 to 61 days after emergence for the rainy and dry seasons, respectively. Weed competition before or after these critical periods had negligible effects on crop yield.