Adaptability of four cassava (Manihot esculenta crantz) cultivars in swampy inland valley ecology

Abstract

Cassava is a popular dry season crop grown to utilize residual soil moisture in inland valleys. Trials to evaluate growth rates of four cultivars (TMS 4(2) 1425, TMS 91/02324, TMS 91/02327 and Isunikankiyan) were conducted along the toposequence in a 4 x 4 Latin square design. Effects of toposequence position, site, year and their interactions as well as of cultivar were significant for Leaf area index (LAI), net assimilation rate (NAR), crop growth rate (CGR), tuberous root bulking rate (TRBR), relative growth rate (RGR) and root yield. LAI, NAR, CGR, TRBR and RGR correlated positively with yield. TMS 91/02324 and TMS 91/02327 with the highest growth indices produced the highest yields. The deep water table site at Alabata had the highest growth indices and yield in valley bottom and the lowest in the fringe, while the shallow water table site at Ibadan recorded higher yield and growth indices in the fringe than the other positions. The shallowest water table depths at Ibadan and Alabata were and below mound surface in valley bottom and fringe, respectively. Valley fringe at Ibadan and valley bottom at Alabata had similar water table depth and they produced the highest growth indices and yield. Shallow water table of below mound surface reduced LAI, TRBR, CGR, RGR and yield, but increased NAR. Drought stress and high radiation, temperature andevaporation reduced yield and growth indices, while well distributed rainfall increased them. Cassava cultivars with high root yields in swampy inland valley are early maturing and maintain high LAI, TRBR, CGR, RGR and NAR under excess soil moisture and drought stress.

**Keywords:** Growth indices, Cassava cultivars, Root yield, Groundwater table depth, Inland valley ecology, Drought stress