Early growth and survival of three miombo woodland indigenous fruit tree species under fertilizer, manure and dry-season irrigation in southern Malawi

Although a large number of miombo tree species bear edible fruits which are important sources of vital nutrients and incomes to rural households, their conservation and cultivation remain challenging because of lack of information on their ecology and management. Therefore, the objective of this study was to evaluate the effects of fertilization, manure application and dry-season irrigation on the early growth and survival of the miombo fruit tree species, Uapaca kirkiana, Sclerocarya birrea and Vanguaria infausta with Mangifera indica as relative control. At 33 months after planting, growth and survival of U. kirkiana and S. birrea were lower in plots that received fertilizer, compost and irrigation compared with those that did not. The best growth and survival in U. kirkiana was obtained when irrigation was applied with neither fertilizer nor manure. The best growth in S. birrea was recorded where plants received irrigation without fertilizer and manure, while survival was highest when none of the treatments was applied. Growth and survival of V. infausta was not affected by manure application, but fertilizer and irrigation increased root collar diameter, leaf, shoot and branch numbers. At 33 months after planting, U. kirkiana and S. birrea had not reached reproductive maturity, while V. infausta and M. indica had started fruiting in the second year. It is concluded that fertilization, manure and irrigation do not increase early growth or survival of U. kirkiana and S. birrea contrary to the commonly held assumption about factors that affect growth and survival in this species. The poor response to fertilizer and dry-season irrigation could be attributed to either their adaptation to infertile soils and unimodal rainfall regimes in their natural stands or delayed response that could not have been observed in the short period of the study.