Amélie Février1, Olivier Payet2 and Arvine Nuckhir1
1eRcane, Saint-Denis de La Réunion, France; fevrier@ercane.re
2CTICS, Saint-Denis de La Réunion, France
Sugarcane is an economic pillar of Réunion, and improving the productivity of the 20 000 ha of sugarcane is a major challenge for this community. Optimising the fertilisation practices is a way to improve this productivity. However, the farming sector is dependent of imported mineral fertilisers, and recent price increases and availability issues question this dependence. However, Réunion produces large quantities of exogenous organic matter (EOM) from livestock farming, human activities and agro-industries. These EOM are used as fertilisers, but the data used to determine nitrogen (N) efficiency come from studies in mainland France, with temperate climate, soils and crops. The Tero project was set up in 2014 to update the N-use efficiency indices for eight EOM for use in sugarcane production. This project consisted of four long-term trials (14 years) to assess the apparent nitrogen recovery (ANR) of eight EOM, and to compare it to the commercial fertilizer (urea) traditionally used in Réunion. Each trial included seven mineral treatments, to obtain N response curves and seven to seventeen organic treatments depending on the trial. The ANRs were calculated for the year of application of the EOM, the year following the application, and two years after application. After seven years of cultivation, the first results show ANRs of EOM ranged between 3% and 26% in the year that the exogenous organic materials were applied to ratoons, while the ANRs of urea ranged between 19% and 30% depending on the trials. There was pedo-climatic variability for both urea and EOM ANRs. Depending on the product used, the N applied to the soil was assimilated by the cane in the years following the application. ANRs varied between 0 and 14% in the second harvest following application, and 0 to 6% in the third harvest after application, depending on the EOM . The amount of nitrogen fertiliser applied could be reduced by taking these efficiencies into account. These new ANRs will be added to our decision-support tool to calculate the amount of EOM applied to fertilise sugarcane.