Root biomass in a mature cacao (Theobroma cacao L.) plantation

A quantitative analysis of the root biomass of and 11 yr cacao plantation is presented. Root biomass values are based on extraction of 100 soil samples of 120 cm3 each, from soil depths of 0 - 15 cm. Root data from greater depths were interpolated from literature. All the samples were collected and analyzed in November, 1980. The total cacao root biomass was estimated with 1038 g m-2 dry weight, or about 10 t ha-1. The rootlets had a mean diameter of 0.22 mm and were localized to about 90 per cent in the upper 10 cm of the soil. Calculation of the rootlet extension resulted in a value of 1200 m m-2, i.e. 12 x 10 exponent 3 km ha-1. This rootlet extension represents about 1 m2 of absorbing root surface per m2 of soil surface. The high rootlet concentration in the upper 3 cm of the soil indicates a mean distance of 2 - 3 mm between rootlets