Abstract
One of the main objectives of the Collaborative Study of Cassava in Africa (COSCA) was to obtain data on the cassava production systems in Sub-Saharan Africa. In Tanzania soils grown to cassava and other major arable crops in 45 villages were sampled in order to assess and compare their fertility status and relate the fertility status to factors which could have given rise to any observed variations. Soils were collected from 0–20 and 20–40 cm depth and 16 physicochemical properties were considered. Both climate and altitude significantly influenced at least 11 of the soil properties in fields grown to cassava. Human population density and cassava mixture significantly influenced particle-size distribution, total nitrogen, organic matter (OM) and exchangeable acidity. The soils of the non-humid and those of the low altitude zones were respectively, on average, more fertile than those of the subhumid and mid-altitude zones. Comparatively, soils grown to cassava were as fertile as or more fertile than soils grown to other arable crops, except in the cases of Mg++, total exchangeable bases (TEB) and effective cation exchange capacity (ECEC) for soils grown to banana or plantain. Based on the rating scale for optimum cassava performance, only nitrogen was found to be lower than the critical minimum required by cassava and thus needs to be applied in most of the soils. On average, the soils of the entire area sampled were generally medium to high in fertility.
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