Weeds is one of the main constraints for annual crop farming. Like for cassava, after twice plowing (deep and shallow) farmers need to spray 2-3 times herbicides and 1-2 times manual weeding. The weeds population is overwhelming if the drought occurs during the first 2 months.
More degraded the soil is more population of weeds there are. Without any alternatives to reduce costs with same efficiency, farmers use herbicides to control the weeds and for any kinds of annual upland crops (maize, pulse crops, cassava).
With remaining tree stumps, the field could not be tilled. The farmers spray herbicide, burn out the dried vegetation and manually plant hybrid corn or cassava by hoe. Nowadays, manual sowing represents a small proportion of lands due the availability of planters.
It takes about 3 years for the smallholders to manually reclaim the forest lands before it could be tilled. Non-selective herbicide is commonly used to prepare the field for maize and cassava. This practice is currently done on hilly field unable to till.