Root biomass plasticity in response to nitrogen fertilization and soil fertility in sugarcane cropping systems

Soil fertility is crucial for plant growth as it influences root development, nutrient uptake, and overall plant health. Optimizing fertilization practices is essential for productivity and sustainability in sugarcane (Saccharum officinarum) cropping systems, especially on Reunion Island, where soil types and climatic conditions vary. The aim of this study was to assess the influence of mineral nitrogen fertilization and soil fertility on sugarcane root development, with particular focus on root biomass production and distribution. The study was conducted across ten sites on Reunion Island, each site representative of one of five soil types in two distinct climatic zones. Using a mechanical auger, root biomass and distribution were measured in fertilized and unfertilized plots down to a depth of 50 cm and at three distances from the row of sugarcane at harvest. Root biomass varied markedly depending on the site: it ranged from 4 to 12 Mg ha-1, corresponding to root-to-shoot ratios varying from 0.10 to 0.43. Root biomass increased by 15 % and root nitrogen concentration decreased by 9 % in unfertilized plots, while root nitrogen mass was not affected. Root biomass was influenced by chemical soil fertility and decreased with declining P availability. Chemical and physical soil properties also influenced the proportion of roots in the superficial soil layers. These findings underscore the plasticity of root biomass allocation in response to soil fertility and fertilization. Given the significant role of roots in soil carbon sequestration, understanding their dynamics is crucial for refining fertilization strategies and enhancing the sustainability of sugarcane cropping systems.