Effect of charcoal and spent engine oil on some growth indices of <i>Rhizophora racemosa</i> g. Mayer grown in garden soil

Abstract

This study investigated the effect of charcoal and spent engine oil on some growth indices of mangrove seedlings Rhizophora racemose G. Mayer grown in garden soil. The aim was to discover means of improving mangrove nursery growth and survival in the Niger Delta area of Nigeria. Rhizophora racemose was planted in garden soil amended with four different treatments: C (Garden soil only), PC (Garden soil + Charcoal), PCSEO (Garden soil + Charcoal + 6% Spent engine oil), and SSEO (Garden soil + 6% Spent engine oil), with three replicates each and randomized complete block design was adopted for the study. The effect of these treatments was monitored biweekly on some growth indices – plant height, leaf area, leaf length, number of leaves and stem girth, except for root length, number of roots, fresh weight, dry weight and chlorophyll content of R. racemosa which were obtained at 18th week after planting. The study revealed that PC treatment had the highest values for plant height, number of leaves, fresh weight, plant girth, root length when compared to other treatments (C, PCSEO and SSEO) while SSEO recorded the least values. Among the treatments, there were significant differences in the plant height, fresh weight and root length of R. racemosa at P = 0.05. The garden soil amended with charcoal improved the performance of R. racemosa than in spent engine oil alone (PC > PCSEO > SSEO). This could be attributed to the presence of heavy metals in spent engine oil. Again, the charcoal amended soil had higher values for growth indices when compared with the control (C) treatment. This suggest that charcoal has the potency of improving garden soil fertility, plant survival and productivity. Therefore, charcoal could be beneficial in environmental conservation, restoration of endangered forest especially the mangroves in the Niger Delta polluted with crude oil. The study recommends that, charcoal should be incorporated in reforestation and afforestation approaches of mangrove forests.