S21 - Session O2 - Banana-n model: a dynamic model to simulate nitrogen balance in agroecological banana cropping systems

Authors: Marie Ruillé *, Elodie Dorey, Marc Dorel

Organic nitrogen (N) fertilizers and the introduction of cover crop could be an alternative to the use of synthetic nitrogen fertilizers in banana cropping systems. But changing agricultural practices modify nitrogen bioavailability in the agrosystem and may ultimately decrease crop yield. We (i) compared banana cropping systems with different cover crop species and different nitrogen fertilizers, and (ii) identified agricultural practices that promote nitrogen restitution and banana yield while minimizing nitrogen losses during the crop cycle. For this, we designed a simple dynamic model to simulate nitrogen balance of banana cropping system in association with a cover crop and organic fertilization over successive crop cycles. This study presents the general structure and formalisms of BANANA-N model mainly based on SIMBA-N model and validated models in scientific literature. BANANA-N model simulates nitrogen dynamics at a weekly time step in banana agrosystems. It includes 6 sub-models: cover crop N uptake, banana N uptake, N leaching, soil organic matter mineralization, crop residue mineralization and added organic matter mineralization. Volatilization and denitrification of nitrogen were not included in the model. Two main improvements were integrated in the model in order to take into account N mineralization from added organic matter and cover crop uptake. Moreover, nitrogen flows in field soil are simulated in two distinctive horizontal layers (0n30 cm, 30n60 cm). BANANA-N model was developed and calibrated in Guadeloupe for 'CIRAD 925' variety over three crop cycles. We simulated scenarios differentiated by nitrogen fertilization (organic versus synthetic) and cover crop species (Brachiaria mutica versus Arachis repens ). Scenarios were evaluated against each other by comparing the simulated soil mineral nitrogen. This study demonstrates the importance of BANANA-N model in developing fertilizer management strategies for designing sustainable banana cropping systems.