In early May of 2007, before the onset of the rainy season, four microcosms were
installed within each plot of the five treatments on all replicate farms. Microcosms
consisted of a 35 cm long section of PVC tubing with an inside diameter of 20.9 cm and
capped with 1 mm plastic mesh on both ends. A single large pit (50 x 50 cm) in each plot
was excavated to a depth of 35 cm and a layer of sand (5cm) was added to the base of
each pit to ensure adequate drainage from the microcosms. Field moist soil removed
from each pit was immediately passed through a 12 mm mesh to remove large rocks and
debris and then thoroughly mixed. Four microcosms were placed in each pit, adjacent to
each other and then filled to a depth of 30 cm with the homogenized soil. Litter additions
to each microcosm were representative of inputs to the whole plots for each treatment
(see Table 1). Microcosms under QSMAS management received a mix of maize residues
from the previous growing season and green leaves from three common tree species
found in the system. Microcosms in SB plots received no residue inputs, as organic
materials under SB management are typically gathered and burned prior to planting. Less
maize residue was applied to microcosms in the QSMAS -F plots to account for the lower
productivity in these plots, while the microcosms under SF received a more diverse mix
litter from 6 tree species with no inputs of maize residue (Table 1). Litter was applied to
the microcosms in QSMAS and SF prior to planting in the main plots in late May