Plant growth and microbial activity in a tropical soil amended with faecal pellets from millipedes and woodlice

The effect of soil fauna-mediated leaf litter (faecal pellets) versus mechanically fragmented (finely ground) leaf litter on biomass production of rice (Oryza sativa, var. Primavera) was assessed in pot tests. Rice seedlings were either grown in soil samples amended with faecal pellets of diplopods and isopods fed on leaf litter of a legume cover crop (Pueraria phaseoloides (Roxb.) Benth) and a peach palm (Bactris gasipaes) or in soil amended with finely ground leaf litter. The addition of faecal pellets caused a significant and dose-related increase in plant biomass compared to pure soil. Ground leaf litter induced a significantly smaller positive effect on plant biomass development with Pueraria litter > Bactris litter > mixed primary forest litter. In contrast, soil microbial biomass development during the 4 weeks plant test was higher in the soil amended with ground litter as compared to soil amended with feacal pellets. The results show a clear positive effect of the soil fauna on soil fertility and indicate differences in the availability of nutrients from the organic substrates to higher plants and soil microorganisms.