Cover crops combined with soil tillage impact the spontaneous species density, richness and diversity in banana cover cropping systems

Abstract

Soil tillage and cover crops impact spontaneous vegetation in agrosystems. Soil tillage destroys seedlings and can affect the soil seedbank. Cover crops compete with naturally occurring spontaneous species. Our aim was to gain insight into how soil tillage (here, the false seedbed technique) and cover crops impact the spontaneous vegetation in fallows preceding banana crops. In a fallowed field in Guadeloupe (French West Indies), two factors were combined in a split-plot design: the soil tillage modality before cover crop sowing (with or without the false seedbed technique) and the cover crop species (Crotalaria spectabilis, Pueraria phaseoloïdes, a 50/50 mix of Brachiaria decumbens + Brachiaria ruziziensis, a spontaneous vegetation control). On a monthly basis, in three permanent quadrats per sub-plot, all spontaneous species were identified and their numbers counted, while calculating the species richness and Shannon’s diversity index. The spontaneous vegetation dynamics contrasted depending on the treatment. From 7 months post-sowing the species density, richness and Shannon index were significantly lower in treatments with B. decumbens + B. ruziziensis and P. phaseoloïdes, while in treatments with C. spectabilis, the species density and richness were significantly higher with than without the false seedbed technique. These effects were probably related to differences in the competitive ability of the cover crop used and, to a lesser extent, to the false seedbed effects on the soil seedbank. This is the first study to show that under a tropical climate, sown cover crop species combined with different soil tillage modalities have substantial impacts on the species density, richness and diversity of the spontaneous plant community over a 1-year period. These results could help farmers in their weed control strategies by providing them with a deeper understanding of the effects of practices on the spontaneous plant community.