INTERCROPPING STRATEGIES FOR SUSTAINABLE WEED MANAGEMENT IN CASSAVA BASED PRODUCTION SYSTEM IN NIGERIA: A REVIEW

Purpose of Work: The paper is a review of field works conducted at varied locations within the Guinea savannah and rain forest zones of Nigeria, as it relates to intercropping strategies for sustainable weed management in cassava based production system. It highlights the common weed species as ranked in order of occurrence in cassava fields as well as the application of intercropping strategies such as the use of plant population density, use of leguminous cover crops and the use of complex crop mixture in controlling weeds, particularly in a cassava based intercropping system.
Methodology: All experiments were conducted using randomized complete block design (RCBD).
Major Findings: The results obtained showed that in a cassava-vegetable cowpea intercrop, sowing vegetable cowpea at the population density of 70,000 plants ha-1 gave the highest percentage (%) ground cover, significantly (P=.05) higher than the rest of the population densities. Weed density significantly (P=.05) reduced as population density of the intercropped vegetable cowpea increased up to 70,000 plants ha-1. Higher stand establishment % and higher ground cover % were respectively, recorded for Mucuna pruriens and Mucuna preta planted in association with cassava as compared to other leguminous cover crops sown in the intercrop. Weed density was recorded lowest with the planting of M. preta in cassava plots. The introduction of M. preta and M. pruriens respectively, gave the highest intercrop yields of cassava tubers (7412 kg ha-1) and maize (855 kg ha-1). Weed population density and weed dry weight were significantly (P=.05) higher under sole cassava as compared to cassava in association with leguminous crops. The complex mixture involving the interplanting of egusi melon with cassava and maize recorded greater weed control (70%) as compared to when cowpea, groundnut and sweet potato were interplanted. This technique produced the highest intercrop yields of 2.7 t ha-1 for maize and 9.6 t ha-1 for cassava. All the weed control techniques employed in intercropping with maize and cassava recorded land equivalent ratio (LER) values greater than 1.00, indicating yield advantage. Interplanting sweet potato into the mixture of cassava and maize not only gave the highest LER value of 2.21, but recorded the highest percentage land saved (54.8%), which could be used for other agricultural purposes. The implication of review showed that, in Nigeria, intercropping is a sustainable technique for weed control and in improving yields of intercrops, particularly in cassava based production system.