Effects of fallow system and cropping frequency upon quantity and composition of earthworm casts uri icon

abstract

  • Concentrations of organic C, total N and exchangeable Ca and Mg in casts were significantly higher than in the 0-15 cm topsoil. Exchangeable Ca and Mg in casts did not significantly differ between treatments, with the exception of significantly higher Mg in casts after three years of P. phaseoloides fallow. Topsoil (0-15 cm) exchangeable Ca and Mg were not correlated with cast exchangeable Ca and Mg,but concentrations of organic C and total N in casts were significantly correlated with organic C and total N in the topsoil. Coefficients of variability of organic C, total N and exchangeable Ca and Mg were about twice as high in the soil than in casts. Significant negative correlations between the cast to soil ratio (cast enrichment factor) of organic C, total N and exchangeable Ca and Mg and the respective concentrations in the soil show that earthworms are increasingly selective in organic carbon and nutrient uptake as these parameters of soil fertility are declining.
  • The quantities of earthworm surface casts were monitored in traditional bush fallow regrowth (BFR), Pueraria phaseoloides live mulch (PLM), Leucaena leucocephala alley cropping (LAC) and undisturbed forest. The fallow systems were planted to maize/cassava intercrop either permanently or for one year after three years of fallow i.e. al 100 and 25% cropping frequencies. Earthworm casting activity was lower in fields cropped after clearing three year old fallow than in the respective permanently cropped fallow management system. The reduction in casting was related both to the degree of biomass removed through burning and to re-establishment of cover crops. Higher exchangeable cation concentration in the soil did not cause increased casting activity.

publication date

  • 1998
  • 1998