Decomposition of Crop Residues in Banana-Based Cropping Systems of Uganda

Abstract

In banana-based cropping systems of Uganda, complex strategies of organic resource management have developed. The traditional method of cultivation includes surface mulching the banana mats with the pseudostems, leaves and peels following harvests. Bananas are frequently intercropped and a wide range of other plant residues are retained as surface mulches. The most common of these intercrops are beans (Phaseolus vulgaris) and maize (Zea mays). The decomposition and nutrient release of banana pseudostems, leaves and peels, 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 effect of soil fauna was estimated by altering the screen openings of the litter 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 (t₅₀). The organic resources decomposed in the order bean trash > banana peel > maize stover = banana pseudostems > banana leaves. Exclusion of soil macrofauna (2–5 mm) delayed decomposition of banana pseudostems, when applied as mulch. When field availability and tissue concentrations are taken into account, banana leaves and bean trash have the greatest potential to recycle N (25 and 29 kg ha⁻¹ yr⁻¹, respectively) and banana leaves and pseudostem recycle the greatest 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 nutrients in this farming system was 69 kg N and 147 kg K ha⁻¹.