Influence of soil fertility status on host response to black Sigatoka and yield of plantain (Musa AAB) in southern Nigeria
The severity of black Sigatoka disease on the first and second cycle plantains managed under varying soil fertility status was assessed using Zero fertilizer and mulch as control, Sawdust mulch (SDM) applied at 20 t/ ha, and 50,100, and 150 kg NPK 20-10-10 /ha, applied sole and in combination with each fertilizer rate in a randomized complete block with three replications. Data were collected on number of functional leaves retained on the plant during the dry season, leaf longevity, number of functional leaves on the plant at flowering (NFLF) and at harvest (NFLH), number of leaves with black leaf streak at stage 5 on the modified Stover Scale (Gauhl, 1994) at the flower stage (NLSF) and at harvest (NLSH) and bunch yield per hectare. Mean number of functional leaves per plant during the dry season and the mean leaf life span were significantly (p< 0.05) higher in mulched + fertilizer treated plantains with 8 to 10 functional leaves per plant compared with 5 to 7 leaves retained on plantains in control/bare plots. Mulched and mulched + fertilizer treated plants had longer mean leaf life span of 10 to 12 weeks in the first generation and 9 to 11 weeks in the second generation. Black sigatoka infection severity on plantains were significantly (p< 0.05) high in nonmulched plantains. Plantains grown under optimum soil fertility management (150 kg NPK 20-10-10/ha + 20 tonnes of sawdust mulch/ha) showed high tolerance to black sigatoka infection and produced the highest bunch yield of 15.7 tonnes/ha.
Key words: Black sigatoka, severity, plantain, soil fertility.