Seasonal effect on Moringa oleifera gaseous exchange and water use efficiency under diverse planting densities

Abstract

The study on Moringa oleifera was conducted over twelve months during 2014-2015 to evaluate the impact of the growing season and varying planting densities on biomass yield and physiological at-tributes under dryland conditions. Trial was established at densities of 5000, 2500, 1667 and 1250 plants ha^-1, with eight replicates. The increase in planting density led to an increase in biomass production. The monthly and seasonal data collected showed significant differences in net photosynthetic rate, transpiration, sub-stomatal CO₂ and stomatal conductance. However, planting densities of M. oleifera had no significant effect on all the gaseous exchange parameters measured. The results further revealed that the amount of carbon dioxide assimilated by the tree is not attributable to photosynthetic and transpiration rates as well as stomatal conductance. Under water shortage condition and high temperature, M. oleifera used an adaptation strategy by reducing stomatal conductance and transpiration and hence increasing water use efficiency. Moringa oleifera thus has the ability to sequester carbon even under water stress conditions. The tree can therefore be recommended for planting at a relatively high density of 5000 plants ha^-1 in many parts of Limpopo province where temperatures are favorable for improved farmers’ livelihoods as well as for climate change mitigation.