Abstract

Four new cassava varieties ( NR 8082, TMS 00033, TMS 91/ 453 and TMS 00447) were fertilized  with NPK ( 20-10-10)  at the rates of  0, 200, 400, and 800 kg/ha  in an experiment with the crop planted early (April)  in 1999 and then late (September) in 2000. Tuber yield was 28% higher in early-planted cassava than in the late cultivation. Yield was reduced by 44% in NR8082, 15% in TMS 00033 and 45% in TMS 00447 as a result of late planting.  Tuber yield from NR 8082 (44t /ha) was the highest for early-planting while TMS 00033 gave the highest yield (31 t/ha) in late planting.  Fertilizer influence on tuber yield was not significant in early-planted cassava. In late-planted cassava, significant reduction in yields was observed from the application of 400 and 800kg/hectare of fertilizer.  Incidence of tuber rot was influenced by varietal differences rather than fertilizer rates. Incidence of rot was lowest in NR8082 (9-10%) and TMS 00033 (10-11%) in both plantings and the severity was mild in all the varieties. TMS 00033, a low cyanide variety, have tuber yields above 30 t/ha in both early and late plantings and is therefore recommended for adoption trials by farmers.

Key words: Early and late planting, cassava varieties and tuber rot.