Modelling of Root Age Influence on Compressive Strength Properties of Cassava Root

The influence of root age and moisture content on compressive strength properties of an improved (TMS 30572) and a local (TME 7) cassava cultivar were investigated. Roots harvested at 12, 15 and 18 months after planting (MAP) were used to determine stress at peak, energy to break and Young's modulus of the roots at moisture contents of 50%, 55%, 60%, 65% and 70% (w.b.). Mean stress at peak, energy to break and Young's modulus of TMS 30572 ranged from 0.61–0.88 N.mm⁻², 0.89–1.13 N.m and 0.92–0.84 N.mm⁻²; 4.80–6.67 N.mm⁻², 5.99–9.21 N.m and 4.55–5.11 N.mm⁻²; and 4.81–9.28 N.mm⁻², 5.27–5.77 N.m and 5.68–8.84 N.mm⁻²at 12, 15 and 18 MAP, respectively. Corresponding values for TME 7 ranged from 0.41–1.06 N.mm⁻², 0.95–1.15 N.m and 1.07–1.30 N.mm⁻²; 3.23–8.18 N.mm⁻², 5.70–8.37 N.m, 5.56–8.04 N.mm⁻²; and 3.22–6.96 N.mm⁻², 4.25–5.58 N.m and 6.69–8.38 N.mm⁻², respectively. Second-order polynomials described the behaviours of the roots. Root age, and not moisture content, influenced the strength of TME 7 roots, while none of the parameters studied influenced toughness and stiffness (p>0.05). Neither age nor moisture content significantly affected the toughness and stiffness of the roots of the two varieties.