Yield response of two cassava (Manihot esculenta Cranz) cultivars to lime appication on an Ultisol in South Eastern Nigeria

摘要

Research into the soil conditions most suitable for profitable cassava production in the tropics has long been neglected, partly due to the assumption that the crop is deep rooting and adapted to soil acidity. However, as new cultivars are developed, it becomes imperative to reassess the concept of cassava tolerance to soil acidity. The objective of this study was to determine the effect of liming on the yield and yield components of two cassava cultivars NR 8082 (high cyanide) and NR 84292 (low cyanide). In a field trial conducted at Umudike (05~029'N, 07~0 33'E), Southern Nigeria, on an Ultisol having pH 4.60 and KCI extr. Al, 0.90 cmol/kg, two cassava cultivars were subjected to lime rates of 0, 0.50, 1.0, 1.50 and 2.0t/ha in the form of hydrated lime. The two cultivars showed a positive response to liming up to a certain level, but a further increase in the rate of application of lime led to decrease in cassava root yield. For cassava cultivars NR 84292 and NR 8082, optimum yields were obtained with the application of 1.0 t/ha and 0.50 t/ha lime respectively. The application of lime significantly (P < 0.05) affected cassava root numbers but had no effect on stem weight. Lime rate x cassava cultivar interaction was significant (P < 0.05) for cassava root yield and root numbers but not for cassava stem weight. The economic analysis of using the various rates of lime on the two cultivars showed that for cultivar NR 8082, the highest benefit/cost ratio of 2.40 was obtained with lime applied at 0.5 t/ha. Increasing the lime rate beyond this value led to decrease in the ratios. The most economic benefit/cost ratio of 1.63 was obtained at the lime rate of 1.0t/ha in the case of cassava NR 84292.