Abstract

We evaluated five varieties of cassava for yield, N accumulation and their effect on soil chemical properties. Soil phosphorus content increased drastically after 14 months of crop growth while soil organic carbon, N and exchangeable K contents reduced during the same period. Fresh root yield ranged from 17 t ha^-1 to 35.9 t ha^-1, while total dry matter production also ranged from about 18 t ha^-1 to about 25 t ha^-1. Total N accumulation in the total plant biomass varied from about 228 kg N ha^-1 to about 288 kg N ha^-1. The amount of total N uptake exported from the soil through crop harvest ranged from about 59 kg N ha^-1to about 123 kg N ha^-1 while the total N uptake recycled into the soil through the return of crop residue ranged from 127 kg N ha^-1 to about 189 kg N ha^-1. The study suggests that cassava varieties with high root dry matter yield have the potential of exporting large quantities of nutrients from the soil while varieties with high leaf litter deposition is likely to recycle substantial amount of the plant nutrient uptake.

Key words: Biomass, leaf litter, nutrients, root dry matter, soil chemical properties.