Influence of canopy structure on yield of cassava cultivars at various toposequences of an inland valley agro ecosystem

Abstract

A two-year trial to evaluate differences in canopy parameters in relation to productivity of cassava was conducted in inland valley ecology in a 4 × 4 Latin square design. Canopy parameters differed between sites, toposequence positions and years due to large differences in water table depth and weather conditions. Leaf number, leaf formation rate, leaf area index, canopy area and stay green ability correlated positively with yield. The improved cultivars with higher values for these parameters had higher yields than the landraces. However, TMS 4(2)1425 with the highest values had super-optimal, while the landrace produced sub-optimal canopy parameters; both of which reduced the yield. TMS 91/02324 and TMS 91/02327 with intermediate values maintained optimal canopy parameters resulting in high yield. Shallow water table (0.20 to 0.45 m below mound top) and drought reduced the canopy parameters and yield, while well distributed rainfall, high humidity and moderate temperatures (19 to 20°C) improved the canopy parameters and yield. Canopy parameters of low yielding landrace were more susceptible to shallow water table and drought than the high yielding improved cultivars. Selection of cultivars with good maintenance of canopy parameters during mid-season drought and late season excess moisture can contribute to increased tuber yield of cassava in inland valley ecology. Key words: Cassava cultivars, water table depth, drought, excess moisture stress, canopy parameters, tuber yield.