Mass Loss and Nutrient Release through Leaching in Tectona grandis and Theobroma cacao leaf litter in Ile-Ife, Nigeria

Tectona grandis and Theobroma cacao are common plantation tree crops planted to replace natural forest in Nigeria because of their faster growth rate and economic values. The changes in land use have marked effects on the soil nutrients and organic matter stock, thereby affecting physical, chemical properties and soil microbial activity. This study looked at the mass loss and rate of leaching of nutrients in the two tree species. Bulk of fallen senescent leaf litters were collected from the plantations, air-dried and thoroughly mixed. Two grammes of each species was weighed into a 500 ml beaker and 250 ml of distilled water added and were retrieved at interval of 0, 24, 48, 72, 96, 120 and 144 hrs, this was replicated six times. The pH, mass loss (%), rate of mass loss (% hr–¹), conductivity (μs), total dissolve solid (mg l–¹), nutrients in leached water were measured. Results showed higher mass loss rate of 0.37 % hr-1 in Tectona grandis compared to 0.29 % hr-1 in Theobroma cacao after 24 hrs. At the end of the study, 1.20%, 5.23%, 6.64% and 8.25% of the initial amount of Ca, Mg, K, and Na in the Theobroma cacao leaf litter; and 2.23%, 1.38%, 7.99%, and 13.077% in Tectona grandis leaf litter were retained. It was observed that 9.27% and 3.71% of the initial amount of N and P were lost from Theobroma cacao leaf litter while, 9.23%, and 8.10% were released in Tectona grandis at the end of the study. The release of P, Ca, K and Na with respect to leaching at the end of the study was better in Tectona grandis and the information of nutrients release will be helpful in selecting the best tree species for plantation establishment in terms of nutrients return for improved productivity.