Abstract

Aims: In Madagascar, agroecological practices to increase and sustain upland rice productivity are based on an intensification of soil ecological processes.

Study Design: The effects of earthworm presence and identity (Pontoscolex corethrurus, Dichogaster saliens, or no earthworms), residue presence and identity [Crotalaria grahamiana (Fabaceae), Desmodium uncinatum (Fabaceae), Stylosanthes guianensis (Fabaceae), Eleusine coracana (Poaceae), Zea mays (Poaceae) or no residues] and residue location (mulched or buried) on nutrient availability and rice growth and yield were investigated in outdoor mesocosms. Thirty-three treatments were managed in a completely random design.

Place and Duration of Study: The experiment was conducted at Andranomanelatra near Antsirabe, Vakinankaratra region, in the highlands of Madagascar in 2016.

Results: Earthworms had no effect on soil nutrient availability and positive effects on plant biomass. Nevertheless, the presence of earthworms increased the shoot:root ratio. The main significant effects on soil properties and crop yields were due to the presence, identity and location of the residues. The addition of Desmodium residues enhanced the total plant biomass, rice grain yields, soil nitrate content and total P uptake by rice. No significant interactive effect was found between earthworms and residues on plant and soil properties.

Conclusion: The most striking finding of the present study was that the identity and location of the residues were the most important factors influencing soil nutrient content, plant growth and crop production, irrespective of earthworm presence.