Nematodes and Weeds Control Effects of Pueraria phaseoloides and Flemingia macrophylla Fallows on Establishment, Survival and Yield of Plantain

The yield of plantain (Musa spp., AAB Simmonds) declines sharply after 1–2 years of cropping in West and Central Africa, due mainly to weeds and nematodes. A trial was carried out from January 2002 to October 2005 under two landuse systems (LUS) comprising 4–5 year-old bush fallow, dominated by Chromolaena odorata (L.) R. M. King & H. Rob, and a 20 year-old secondary forest, in three villages in southern Cameroon, to assess the effectiveness of Pueraria phaseoloides and Flemingia macrophylla as planted fallows for weed suppression and reduction in nematode damage of the plantain root system, and determine the yield response of different plantain sucker types to the weed suppression and reduced nematode damage. In each LUS, the treatments were a factorial combination of three levels of fallow system and four levels of plantain sucker type arranged in a randomised complete block design. Total above-ground biomass production of P. phaseoloides was 7.45 Mg ha-1, 4.2 times higher than F. macrophylla (1.78 Mg ha-1; P < 0.05). The high biomass of P. phaseoloides resulted in a significantly greater reduction in total weed biomass compared to F. macrophylla in both wet and dry seasons. Comparing the planted fallows, a sustained reduction in soil nematodes population was only under P. phaseoloides. Plantain establishment and survival rates were of decreasing order: PIF (nursery)-derived “Essong” > Boiling water-treated “Essong” > Untreated “Essong”. P. phaseoloides produced significantly (P < 0.05) the highest plantain yield. There were no differences between the natural regrowth and F. macrophylla for all the plantain yield parameters. Sanitizing suckers (boiling and nursery-derived) increased actual yield and quantity of edible bunches by 35% and 26%, respectively, compared to the untreated. It was concluded that P. phaseoloides had the greatest positive effect on the growth and yield of plantain. Introduction In West and Central Africa, 25% of the carbohydrates and 10% of the food energy of approximately 70 million people are derived from plantains (Ortiz & Vuylsteke, 1996; Robinson, 1996). In addition, plantain production provides reliable family income and job opportunities (Robinson, 2000). For example, in south-eastern Nigeria, smallholder farmers generate up to 30% of their income through plantain cultivation (Pasberg-Gauhl & Gauhl, 1996), while in southern Cameroon and Ghana, plantain is one of the most important food cash crops and, therefore, vital for cash income generation of smallholder farmers (Dury et al., 2002; Schill et al., 1996). However, yield of plantain declines after 1–2 years of cropping with its attendant economic consequences. The decline usually manifests through stunting of plants, reduction in bunch weight and toppling of plants. Some of the attributable factors are low soil fertility, root damage by nematodes and weeds competition. Application of Pueraria phaseoloides and Flemingia macrophylla as planted fallows have been demonstrated to cause an increase in the yield of associated crops through improved and sustained soil fertility (Kang et al., 1997). Yet, regarding the contribution of these planted fallows to crop yield through nematodes and weeds control, scanty literature is available in West and Central Africa. The paper focuses on these untapped contributory benefits. These benefits might collectively allow increased plantain yields through reduced plant losses, heavier bunches and a longer productive life span. The objectives of the study, therefore, were to (1) assess the effectiveness of Pueraria phaseoloides and Flemingia macrophylla as planted fallows for weed suppression and reduction in nematode damage of the plantain root system, and (2) determine the yield response of different plantain sucker types to the weed suppression and reduced nematode damage.