Silicon fertigation modulates antioxidant metabolism and the growth of common beans grown in the field under water stress with and without potassium supplementation

Common bean plants are sensitive to water deficit, and one strategy to reverse this damage would be to use silicon (Si) and potassium (K). Silicon may alleviate water-deficit injury by modulating antioxidant enzymes and compatible solutes, including proline and phenolic compounds to mitigate abiotic stress, including as water deficit. However, there is a lack of research on field-grown beans focusing on the antioxidant mechanisms involved. Furthermore, limited information is available on the responses of Si-fertigated beans to water deficit under field conditions with and without supplemental K. Therefore, this research was conducted to investigate the biochemical and physiological responses of bean plants under three water regimes and Si doses applied via fertigation, under conditions with and without supplemental K fertilization. To this end, two field experiments were conducted with bean plants under conditions without (-K) and with (+ K) supplemental K fertilization, with the initial soil K content corresponding to 6.4 mmolc dm⁻³. The experiments were conducted independently and each consisted of a 3 × 4 factorial arrangements, with three water regimes (80%, 60%, and 40% of soil water-holding capacity (field capacity) and four Si rates (0, 4, 8, and 12 kg ha⁻¹) applied via fertigation. A split-plot scheme was used in a randomized complete block design with four replicates, with water regime assigned to the main plots and Si rate assigned to the subplots. The two experiments were analyzed separately. The biochemical analyses performed in leaves included antioxidant enzyme activities (SOD, APX, and GPOX), proline content, phenolic compounds, and lipid peroxidation. Shoot dry mass production was also determined. Fertilization with Si via fertigation at doses (4 to 8 kg ha⁻¹) showed potential to be an important strategy for sustainable bean cultivation, especially in areas with moderate to severe water restrictions, with or without complementary K fertilization. The effects are due to the modulation of SOD, APX, and GPOX enzyme activity, in addition to increasing the content of proline and phenolic compounds. These results highlight the potential of silicon fertigation to enhance silicon-mediated drought responses by modulating antioxidant metabolism—including enzymatic and non-enzymatic antioxidant defenses—in the common bean.