Decomposition of crop residues in banana-based cropping systems of Uganda

In banana-based cropping systems of Uganda, complex strategies of organic r esource management have developed. The traditional method of cultivation in cludes surface mulching the banana mats with the pseudostems, leaves and pe els following harvests. Bananas are frequently intercropped and a wide rang e of other plant residues are retained as surface mulches. The most common of these intercrops are beans (Phaseolus vulgaris) and maize (Zen mays). Th e decomposition and nutrient release of banana pseudostems, leaves and peel s, maize stover and bean trash was studied. Black plastic litter bags were placed in the field and recovered after 0, 2, 4, 8, 16 and 32 weeks. The ef fect of soil fauna was estimated by altering the screen openings of the lit ter bags (2 vs 5 mm). For fresh banana pseudostems, litter bags were place on the surface or buried to study the effect of soil incorporation. Litter materials were analysed for C, N, P, K and lignin. The results were fit to first order exponential decline and the decomposition coefficient (k) used to calculate the time to 50% mass and nutrient loss (t(50)). The organic re sources decomposed in the order bean trash > banana peel > maize stover = b anana pseudostems > banana leaves. Exclusion of soil macrofauna (2-5 mm) de layed decomposition of banana pseudostems, when applied as mulch. When fiel d availability and tissue concentrations are taken into account, banana lea ves and bean trash have the greatest potential to recycle N (25 and 29 kg h a(-1) y(-1), respectively) and banana leaves and pseudostem recycle the gre atest amounts of K (43 and 26 kg ha(-1) yr(-1)). The combined contribution of banana leaves, pseudostems, maize stover and bean trash to recycling nut rients in this farming system was 69 kg N and 147 kg K ha(-1).