Effect of trees on photosynthesis rates in 40 day old dry season sorghum [Sorghum bicolour (L.) Moench] in the semi-arid zone of Nigeria

Abstract

Studies of the effect of 10 yeal old Balanites aegyptiaca, Prosopis juliflora and Acacia nilotica on photosynthesis rate in 40 day old dry season sorghum [Sorghum bicolour (L.) Moench] were conducted in agroforestry site in a Semi-arid area of Nigeria. Sorghum was planted at 1m interval between trees and no tree controls. Diurnal trends of Photosynthetically Active Radiation (PAR), Stomatal conductance, (gs) transpiration rate (E), assimilation rate (A) and water use efficiency (A/E) were measured using an Infra Red Gas Analizer. The result showed that the assimilation rate of sorghum varied with tree species. B. aegyptiaca reduced PAR to a smaller extent as a result, assimilation, stomatal conductance, and water use efficiency was highest in sorghum intercropped with this species followed by P. juliflora and least was in sorghum intercropped with A. nilotica. Reduced assimilation of sorghum intercropped with P. juliflora and A. nilotica was as a result of reduced incident radiation and increased competition for limited moisture. Increased rate of photosynthesis can lead to high biomass and yield. It can be concluded that B. aegyptiaca can be integrated as part of Semi-arid agroforestry and when pruning is applied to P. juliflora and A. nilotica to reduce their level of competition. It therefore, shows that with appropriate choice of tree species it is possible to maintain a sustainable agroforestry system in the Semi-arid areas.