Vinasse enhances sugarcane roots in a sandy brazilian soil

In Brazil, liquid residues (vinasse) from ethanol production are commonly used as fertigation for sugarcane cultivation. The objectives of this study were to evaluate the effect of vinasse application on sugarcane root density and rooting depth. A 2-year field experiment was conducted using three vinasse fertigation treatments, with 3 replications, as follows: Year 1 - control (no vinasse, dose 0), 140 m3 vinasse per ha (dose 1), and 280 m3 per ha (dose 2) and Year 2 - control, 170 m3 per ha (dose 1), and 340 m3 per ha (dose 2). After 12 months of vinasse application, soil trenches (1.5 m depth by 1.2 m wide) were opened within the sugarcane row to evaluate the root system. A metal grid, (1.5 m × 1.2 m) was fitted in the trenches and root number and density (cm of roots per cm3 of soil) were evaluated and a root system model for each treatment was obtained. Following the sugarcane harvest, vinasse fertigations were continued for the second crop cycle, followed by another root growth evaluation. Since vinasse is a nutrient-containing organic residue, enhanced soil fertility from the vinasse applications influenced root growth and rooting depth, particularly within the soil surface layer. Although a few roots were found below 0.6 m depth, most of the increased root growth with vinasse application was found within the surface 0.3 m soil profile. Relative to the control, root density with dose 2 vinasse fertigation increased by 34% (top 0.1 m soil layer), 122% (0.1 to 0.2 m), and 36% (0.2 to 0.3 m). Year 2 results were similar, with dose 2 fertigation resulting in 128% greater root densities in the 0.2 to 0.3 m soil profile relative to the control. We also found linear correlations between base saturation with soil depth and root number and density. These results indicate that successive fertigations with vinasse promote soil fertility improvements and consequently large and deep root systems. (Résumé d'auteur