Influence of crop age on nutritional quality of fresh roots from popular coastal Kenyan cassava varieties

Cassava is an important crop in coastal Kenya commonly harvested at 12 months after planting but earlier during food shortages. Effect of early harvesting on root quality has not been well established. Varieties Tajirika, Karembo and Kibanda Meno (roots) were harvested at different ages from Agricultural Research Centres, and studied for pysicochemical characterstics. Results showed significant (P < 0.05) interaction effect of varieties and crop age on dry matter, starch, carbohydrate, energy, fiber, ash and hydrogen cyanide contents. Karembo and Tajirika had peak dry matter (43.42% and 41.42%, respectively) at 12 months while the peak for Kibanda Meno was 44.99% at 9 months. Mean starch content varied with variety; Karembo (27.3 %), Kibanda Meno (27.4 %), and Tajirika (28.5%). Karembo and Tajirika had peak carbohydrates at 12 months while the peak for Kibandameno was at 9 months. Vitamin C was highest at 6 months for Karembo (6.4 mg/100g). Kibanda Meno and Tajirika had highest vitamin C (6.1 and 7.0 mg/100g, respectively) at 9 months. Iron was highest at 3 months for Karembo (3.63 mg/100g) and Tajirika (5.33 mg/100g) but at 9 months for Kibandameno - 7.12 mg/100g. Peak Zinc was for Karembo (2.1 mg/100g) at 6 months Kibandameno (1.94 mg/ 100g) and Tajirika (1.75mg /100g) at 12 months. While hydrogen cyanide increased from 8.6 to 9.3% in Karembo between 9 and 12 months, it decreased from 7.8 to 5.2% and from 5.1 to 4.5% on Tajirika and Kibandameno, respectively. The results indicate that Kibandameno and Tajirika can be harvested as from nine months after planting.