Proper weed management

Weeds can reduce cassava yields by competing with the cassava crop for moisture, nutrients, space and light. Slow initial development of stem cuttings/sprouts makes cassava susceptible to weed competition in the first 3 to 4 months. Weeds may also harbour pests and diseases or physically injure cassava plants and root tubers. For these reasons, close attention should be paid to weed control in the field in an effort to grow a healthy crop and obtain high yields of cassava.

Common weeds affecting cassava production in Africa are:

• Grasses such as the feathery Pennisetum (Pennisetum polystachion), the  spear grass (Imperata cylindrica) and the guinea grass (Panicum maximum)
• Sedges, particularly Mariscus alternifolius and Cyperus rotundus
• Broadleaf weeds such as Siam weed (Chromolaena odorata), giant sensitive weed (Mimosa invisa) and goat weed (Ageratum conyzoides) 

Under organic farming conditions, in order to manage weeds, it is important to combine different practices, from land preparation, planting to post-planting stages of growing cassava. These practices include:

i. Practices at planting - Proper land preparation, for example by cleaning cassava seedbeds of weed rhizomes, stolons and tubers, reduces weed pressure by root weeds.  Growing fast growing cassava varieties with branching habit may contribute to weed suppression. Mulching cassava seedbeds with dead plant foliage or using cover crops as live mulch on seedbeds prevents early germination of seed weeds. Planting cassava in association with other crops, especially dense-covering leguminous species, ensures good weed suppression between the rows, and provides valuable nitrogen to the cassava crop. Adopting suitable planting distances is another possibility to improve the competitiveness of the cassava crop against weeds.

ii. Practices after planting - Weeding by hand hoeing or hand pulling of the weeds in its early stages prevents weeds from competing with cassava root tuber formation and expansion. Weeds may also be controlled by slashing, especially in mature cassava gardens just to reduce the ability of the weeds to produce seeds and compete strongly with the crop.