Residual effect of silicate fertilization on ratoon sugarcane under water deficit conditions: plant biomass, nutrient element concentrations, and Si:C:N:P stoichiometric ratios

Background and objectives Silicon (Si) has been widely reported to enhance tolerance to abiotic stresses, including drought, in several crops. However, the long-term effects of soil-applied Si remain insufficiently explored. This study aimed to assess dry matter production, plant nutritional status, C:N:P:Si stoichiometry, and soil Si availability in ratoon sugarcane under water deficit and the residual effect of an amorphous silica-derived fertilizer (ASF). Methods Ratoon sugarcane was grown under two levels, 40% or 80%, of maximum water retention capacity (MWRC) and four residual Si rates (0, 78, 117, and 156 kg ha⁻ 1 ) applied in the previous cycle. Biomass production, leaf nutrient concentrations, uptake of Si and macronutrients (N, P, K, Ca, Mg, and C) and, C:N:P:Si stoichiometric ratios, and soil Si concentrations were determined. Results The 80% MWRC treatment combined with 156 kg ha⁻ 1 promoted increases of 34% in leaf and 78% in stalk dry matter relative to the 40% MWRC treatment. Leaf Si concentration rose from 2.47 to 6.64 g kg⁻ 1 between 0 and 156 kg ha⁻ 1 . At 40% MWRC, the 156 kg ha⁻ 1 Si rate increased leaf N and P concentrations by 27% and 84%, respectively, compared with the control. The lowest soil Si concentrations were observed in the soil 15–30 cm layer, with mean values of 9.76 and 10.22 mg dm⁻ 3 under 40% and 80% MWRC, respectively. Conclusion Residual Si significantly improved biomass production and leaf nutritional status of ratoon sugarcane under water deficit. The nutrient extraction and export sequence for cultivar RB041443 was K > N > Si > Ca > P > Mg.