Effect of Integrated Soil Fertility Management on Disease Severity and Cassava Quality in Southern Cote dIvoire

Cassava production in southern Côte d’Ivoire is constrained by the lack of sustainable farming technologies, such as scarcity of drought and disease resistant cassava varieties, fertilizer and pesticides inputs. This study aims to evaluate the effects of integrated soil fertility management (ISFM) systems on severity of cassava mosaic and anthracnose diseases and on cassava quality parameters (dry matter, starch and hydrogen cyanide contents). To this end, field experiments were carried out at two locations (Dabou and Bingerville) during the 2012-2013 cropping season, as a split-split-plot design with three factors in three replications: cassava genotype (improved varieties Yavo, Bocou 1 and local variety Yace), cassava spacing (2 x 0.5 m and 1 x 1 m), and nutrient management (manure at 5 t ha-1 or mineral NPK fertilizer at 50 kg ha-1, and legume intercropping with cowpea or groundnut). Overall, nutrient management did not affect the severity of both cassava diseases. Cassava mosaic disease (CMD) was less prominent for improved varieties Yavo and Bocou 1 (average scores of 1.1 and 1.2, respectively), compared to the local variety Yace which scored 2.8 on a 1-5 scale. In general, the ISFM treatments did not significantly affect cassava tuber quality. HCN content of tubers was decreased when more K was added through manure recommended dose application. Dry matter content was ca.10 % lower in Bingerville (lower fertility site) for both varieties Yace and Bocou 1 in treatment with cowpea and without fertilizer addition. The ISFM system that provided resilience to CMD and sustained quality cassava production appears as a suitable strategy for achieving sustainable intensification of cassava cultivation. Adoption of this technology depends on the ability of smallholder farmers to own or purchase nutrients resources and improved cassava genotypes.