Abstract:
Chemistry, time course of decomposition, nutrient release pattern and nutrient resorption
efficiency of leaf litter of Gliricidia sepium, Acacia auriculiformis, Acacia mangium, Macaranga
peltata, Alstonia macrophylla, Artocarpus integrifolia, Artocarpus altilis, Terminalia calappa,
and Mangifera indica were investigated using the litter bag technique.
Considerable inter-specific variations in the above parameters were observed in the leaf
litters. As regards percent N, P, K, Ca, and Mg, the values observed varied from 0.39 to 1.92,
0.025 to 0.17, 0.16 to 0.95, 1.76 to 2.57 and 0.22 to 0.51, respectively. The highest
concentrations of N, P, K, Ca and Mg were observed in G. sepium, A. altilis, A. altilis, A.
integrifolia and A. macrophylla, respectively. A. macrophylla, M. indica and A. mangium had
the highest concentrations of carbon (42.39%), lignin (22.99%) and cellulose (32.77%),
respectively. A salient feature in the leaf litter of M. indica was that it had the lowest
concentrations of N (0.39%) and cellulose (14.59%) and the highest concentration of lignin c,
(22.99%), with a lignin/N ratio of 58.21 and C/N ratio of 92.71.
G. sepium showed the greatest biomass loss, losing as much as 60% of its dry weight, 30
days after placement. In contrast, M. indica had the lowest rate of decomposition. The
decomposition constant of the species varied from 1.66 (M indica) to 8.46 yr'1 (G. sepium). The
half-life-of litter types ranged from 29 (G. sepium) to 152 days (M indica). Decomposition rates
were positively correlated with the per cent initial N (r = 0.85, p<0.01) and negatively correlated
with the C/N ratio (r = 0.58, p < 0.01).
Considerable inter-specific variations in nutrient release pattern were observed among
litter types, except for K. G. septum and A. ciuriculiformis lost over 50% of their initial N
content by 30 days, whereas A. altilis, T. catappa and M. indica immobilized N from the soil.
The per cent N immobilized ranged from 4 to 20 while M. indica recorded the highest value.
Except A. altilis, other species released P during the first month of decomposition. A. altilis
immobilized P, which amounted to 28%. K was a highly leachable element in the soil, and all
the species, except M. indica, lost more than 70-80 % of their initial K content in 30 days.
Nutrient release pattern was correlated to mass loss with a few exceptions for K and P. Nitrogen
loss was positively correlated with the initial N content (r=0.44, p < 0.05) and was negatively
correlated with the C/ N ratio (r=0.58, p<0.05). Potassium release pattern showed a positive
correlation with the C/ K ratio (r=0.51, p<0.05).
Significant inter-specific differences in nitrogen resorption efficiency (NRE) were
observed (p<0.05) with T. catappa and M. indica showing higher NRE (54.58 and 48.78%,
respectively) while G. sepium showing the lowest (28.94%). The NRE was negatively correlated
with the initial N concentration of leaves in mature stage of all species (r=0.58, p<0.05). These
findings prove useful in identifying suitable combinations of agroforestry tree species for
sustainable soil fertility management.
