Estimating fruit yield from Vitex payos (Lour) Merr. In semi-arid Eastern province of Kenya: application of allometric equations.

Abstract

Vitex payos (Lour) Merr. is a common species in the semi-arid areas of Eastern Kenya. It is a favoured species and is frequently maintained in homestead plots and arable fields in an agroforestry situation. Although the abundance and popularity of Vitex payos has led to the commercialisation of its fruits, their quantities to sustainability support cottage industries in the rural areas has not been considered. Vitex payos trees were surveyed during fruit season and the quantity of fruits for 120 trees distributed on farm lands and bushlands in three districts counted per tree. Mean fruit yield was significantly higher from farm trees (>6145 fruits per tree) than trees in bushlands areas (>4154 fruits per tree), even after accounting for differences in tree size. Few cases of trees with over 21,000 fruits were also recorded from both land uses. Although, the majority of the trees produce <5000 fruits per tree per year, though purposeful selection of germplasm in its wide natural range, production could be increased up to four fold. A fairly accurate prediction of fruits per tree and consequently the quantity available from the farms could be achieved through use of a combined logarithmic and inverse transformation equations using the crown diameter and the tree height. However, considering that the Vitex payos grows in more diverse dryland areas in Kenya including the Eastern, Coastal and Central regions, it is prudent to collect more data from all these areas and test the validity of the equation developed in this study for wide-scale application as a management tool.