Simulation of the growth of banana (Musa spp.) cultivated on cover-crop with simplified indicators of soil water and nitrogen availability and integrated plant traits

To reduce chemical inputs while maintaining crop yield, disturbed ecosystem functions must be restored, for example by cover-crops. In these cropping systems, because of competition between species, soil resources must be carefully managed. Dedicated tools and models are needed that account for the adverse effects of the cover-crop on the cash crop in terms of resource availability. Besides classical agronomic calculations of stress indices, which are difficult to generalize and require numerous parameters, recent work in ecology has related plant traits, like the biomass accumulated, to the resource availability during the whole plant cycle. Following such a simple approach, the objectives of this study were (i) to determine the effects of water and nitrogen limitations on banana growth and development and to test whether simple integrated traits can highlight the effects of these stresses on banana growth, (ii) to parameterize a simple generic module of soil water and nitrogen availability linked to SIMBA GROW, the growth module of the banana crop model SIMBA, (iii) to assess the ability of the model to simulate banana growth and development in the environmental conditions of a banana/cover-crop system, with particular attention on the effects of changes in plot temperature on model outputs. Three experiments were conducted on whole production cycles to investigate the effects of different water regimes, different nitrogen fertilization levels, and the cover-crop Neonotonia wightii on banana growth, nutritional status, and date of flowering. Results showed low nitrogen availability affected banana growth only weakly but decreased leaf nitrogen content and delayed flowering. Low water availability delayed flowering and decreased banana growth. In both cases, the delayed flowering allowed longer banana growth, which balanced the negative effect of low availability on the growth rate. The cover-crop modified both the rooting depth of the banana, and thus the amount of resources accessible to the banana roots, and the plot microclimate, especially air temperature. The model correctly reproduced the differences of date of flowering and leaf area index at flowering for a first cycle of production between a bare-soil and a cover-crop system, provided air temperature was reduced by 2-3% due to the cover-crop. To conclude, this study showed that in fairly constant environmental conditions (temperature, radiation and rainfall) a simplified model using resource availability over the growing period and integrated plant traits satisfactorily simulates banana growth in an intercropped system. (Résumé d'auteur)