Abstract :
Decomposition of Millettia thonningii (Schumach and Thonn) Bak fine roots (≤2 mm) and coarse roots (2-5 mm) was conducted at IITA Ibadan, south-western Nigeria. The study investigated the effect of soil depths, root size and chemical composition of the roots on decomposition, mineralization and immobilization of nutrients. The roots were put in 2 mm mesh-bags and buried at three soil depths; 1.5, 15, and 30 cm and evaluated for 210 days. Decomposition of fine and coarse roots was significantly (pphosphorus (P)>nitrogen (N)>magnesium (Mg)>calcium (Ca), K>P>N>Mg>Ca, and K>P>N=Mg>Ca respectively. The nutrient release patterns of coarse roots at 1.5, 15 and 30 cm soil depths were: K>Mg>N>P>Ca, K>N>Mg>P>Ca and K>N>Mg>P>Ca respectively. The results therefore indicate that soil depth and root sizes have major influence on decomposition and
mineralization of nutrients though polyphenol concentrations, C: N and L: N ratios also influenced these biological processes.
Keyword :
Mineralization, Immobilization, Decomposition Constant, Nutrient Release Constant Rate, Half-life and Lignin: Nitrogen Ratio