AD Seechurn Sookun, Y Ramchurun, S Seeruttun and A Gaungoo
Mauritius Sugarcane Industry Research Institute, Mauritius Cane Industry Authority, Mauritius; arouna.seechurn@msiri.mu
Sugarcane production is often impaired by factors related to loss of soil fertility and severe weed infestations, causing high usage of N fertilizers and herbicides, respectively. Integrating leguminous crops in sugarcane as fallow-breaks was identified as one of the pillars of new cropping systems to mitigate the general yield decline observed in the Mauritian sugar industry since the 1990s. The potential of leguminous crops incorporated in the interrow of ratoon crops was assessed for their capacity to fix N and improve weed control. The initial trial consisted of sowing Lablab purpureus cv Highworth in single or dual rows at a seed rate between 15 and 25 kg ha-1 through the trash blanket using a modified sowing machine. Preliminary results showed that the L. purpureus provided good weed control in all the trials but showed a tendency to twine on the cane leaves and the N fixation was not as effective as when sown in rotational lands. Succeeding trials explored the possibility of inducing localised tillage in the legume seed planting zone following inoculation of the latter with specific rhizobium strains; an improvement in fixation was noted thereafter. Canavalia ensiformis, compared to the Lablab, did not show any twinning on cane leaves due to its morphological characteristics and showed satisfactory weed suppression. Multiplication of C. ensiformis seeds is in progress before its industrial adoption as a companion crop in ratoon crops is recommended. This research demonstrates the potential of companion leguminous crops to improve soil health and reduce the reliance on synthetic nitrogen fertilizers in sugarcane production.