Does the application of mineral and organic fertilizer affect cassava tuber quality? An evidence from Zambia

Cassava is cheap enough to be grown by both the poor and rich farmers in Africa and elsewhere. It is the second most important food security crop in Zambia, next to maize. However, the productivity is very low compared to the yield potential of the crop. To increase yield, extension workers advise farmers to apply fertilizer, but the effect of fertilizer application on cassava tuber quality, mainly to Hydrogen Cyanide (HCN) is not known. This research aimed at understanding the effect of application of both organic and inorganic fertilizer on cassava tuber quality. Four levels of organic fertilizer (0, 1.4, 2.8, and 4.2 t/ha) of chicken manure and four levels of mineral fertilizer (0, 50-11-41.5, 100-22-83, and 150-33-124.5 kg/ha) N–P–K were factorially combined in RCBD and set in two agroecologies of Zambia. The result showed that moisture and sugar content of cassava tubers declined following an increased application of mineral fertilizer, with an average content of 9.21% and 4.22%, respectively. However, the decline in sugar and moisture was not statistically significant between the treatments. Conversely, no clear trend in HCN content was observed following the application of mineral fertilizer. Similarly, no clear trend was observed with the application of organic fertilizer for all the assessed cassava qualities. The application of mineral and organic fertilizer also showed an additive effect – no interaction between the two fertilizer types. Therefore, we conclude that neither organic nor mineral fertilizer application affects cassava tuber quality, especially the sugar and HCN content. Based on the present results, it is advisable to repeat the experiment and see the effect on other varieties to fully understand the effect of cassava fertilization on tuber quality in the Zambian conditions.