LEAF LITTER DECOMPOSITION AND CARBON-DIOXIDE EVOLUTION OF SOME AGROFORESTRY FALLOW SPECIES IN SOUTHERN NIGERIA

Decomposition of the leaf litter of Acioa barteri, Centrosema pubescens and Chromolaena odorata (Syn. Eupatorium odorata) was studied in the laboratory using the litterbag technique. The same litterbag technique was used for the leaf litter decomposition of A. barteri and Centrosema pubescens at Ozala and Nsukka, respectively. Carbon dioxide evolution for the three species was studied in the laboratory for 52 weeks. Acioa barteri and Centrosema pubescens had turnover coefficients (k1) of 1.4 and 1.5 and also litter half-lives of 2 5.1 and 23.4 weeks, respectively. In the laboratory, Chromolaena odorata and Centrosema pubescens attained 100% decomposition at Weeks 8 and 16 respectively, while A. barteri had 85.3% at Week 48. However, under field conditions at Week 48, Centrosema pubescens attained 85% weight loss while A. barteri had 86.7%, a trend similar to its leaf litter decomposition value under field conditions. Carbon dioxide evolution for all three species was significantly greater during the first 4 weeks and thereafter declined steadily. The control (top soil only), however, had the least mean periodic CO2 evolution followed by soil + A. barteri.