Nutrient release from decomposing leaf mulches of karite (Vitellaria paradoxa) and nere (Parkia biglobosa) under semi-arid conditions in Burkina Faso, West Africa

Information on decomposition and nutrient release from leaf litter of trees in agroforestry parkland systems in Sub-Saharan Africa is scarce despite the significant role of these trees on soil fertility improvement and maintenance. Decomposition and nutrient release patterns from pruned leaves of the two most common species of parklands of the semi-arid zone of West Africa: Vitellaria paradoxa C.F. Gaertn (known locally as karite) and Parkia biglobosa (Jacq.) Benth. (known locally as nere), were investigated by a litter-tube study in Burkina Faso. Litter quality, methods of leaf exposure to the soil and combination with fertilizers were the factors studied. Leaves of nere had a higher nutrient content (C, N, P, Ca) and contained more ash and lignin than leaves of karite. Karite leaves had a greater content of K, cellulose and polyphenols. The pruned leaves of karite and nere showed two distinct decomposition patterns. Nere leaves decomposed more rapidly, with less than 32% of the initial weight remaining after the rainy season (4 months) while karite leaves decomposed more slowly with 43% of the leaf litter remaining after the rainy season. Addition of urea and compost did not significantly affect the rate of decomposition. Significant interaction was observed between species and method of leaf exposure for the first sampling date. Leaf litter of nere buried in soil gave the highest weight loss (34% of the initial mass in 1 month) compared with exposed leaf litter of nere and karite, and buried leaf litter of karite. Except for N, nutrient release patterns were similar for both species but the nutrient release rates were higher for nere leaves compared with karite leaves. N was immobilised in karite leaves most likely due to low N and high phenolic content. The rate of nutrient release from karite leaves followed the general trend K>P>N.