Abstract

Field experiments were conducted between 2017 and 2018 at Forestry Research Institute of Nigeria, Humid Forest Research Station, Umuahia, South east Nigeria, to study litter decomposition and nutrient release dynamics in Allanblackia floribunda (oliv) agroforestry system. The experiments were all laid out in a randomized complete block design with three replications. The litter bag method was employed for the decomposition study. The C:N ratio was 10.6:1. The cumulative mean leaf litter decomposition at 48 weeks after litter placement (WALP) was 91.0%, with a biphasic mode of decay, having an initial rapid phase of mass loss (4 – 24 WALP) and a later slower phase (28 – 48WALP). Leaf litter half-life was obtained at 8 WALP while the turn over coefficient k (decay constant) was 4.62/year. The percentage cumulative mean nutrient release for N, P, K, Ca and Mg increased up to 24 or 28 WALP and thereafter stabilized up to 40 WALP, after which a slight decline in P, K, Ca and Mg and a significant drop in nitrogen occurred. However, Organic carbon increased significantly up to 32 WALP, beyond which no significant changes occurred in the cumulative release from the leaf litter. The high rate of litter decomposition and subsequent release of nutrient make A. floribunda leaf litter a good source of organic manure for soil fertility restoration and improved growth and yield of arable crops in the humid tropical environment of south east Nigeria.

Key Words: Litter decomposition, Nutrient release, Allanblackia floribunda, Agroforestry systems