Silicon and Potassium Fertilization Upgrade Resilience in Bell Pepper against Salt Stress through Boosting Root Growth and Fruit Yield

Bell peppers are highly sensitive to salt stress, posing significant challenges for sustainable vegetables production especially bell pepper under suboptimal climatic conditions. Given the economic importance of bell peppers, enhancing their tolerance to salinity stress is a critical research focus over period. Silicon (Si) and potassium (K) and are crucial elements that have potential to combat salt stress significantly. This study aimed to investigate influential role of Si and K fertilization on root growth, physiological response, and fruit yield of bell pepper under salt stress. The factorial experiment included six fertilizer doses (F0: control- recommended fertilizer dose (RDF); F1: RDF + K30 (35 kg ha-1 K); F2: RDF + 60 kg ha-1 Si (soil); F3: RDF + K30 (35 kg ha-1 K) + 60 kg ha-1 Si (soil); F4: RDF + 100 ppm Si (foliar), and F5: RDF + K30 (35 kg ha-1 K) + 100 ppm Si (foliar) and five water salinity levels (control- 0.54, 3, 6, 9, and 12 dS m-1). Results revealed that root morphological traits particularly root biomass, root-shoot ratio, root length and root length density were significantly improved by RDF + K30 (35 kg ha-1 K) + 60 kg ha-1 Si (soil), followed by RDF + K30 (35 kg ha-1 K) + 100 ppm Si (foliar). At 12 dS m-1 salinity level, about 53% and 55% higher root and shoot biomass was reported at RDF + K30 (35 kg ha-1 K) + 60 kg ha-1 Si (soil) in compare to control. Leaf proline accumulation was increased with rising salinity levels which maximized by 51% at RDF + K30 (35 kg ha-1 K) + 60 kg ha-1 Si (soil) followed by 43% increase at RDF + K30 (35 kg ha-1 K) + Si (foliar) over control at 12 dS m-1 salinity level. Enhanced fruit yield was observed with various Si and K fertilization combinations, where RDF + K30 (35 kg ha-1 K) + 60 kg ha-1 Si (soil) shown a 62% and 40% higher yield in compare to control at 9 and 12 dS m-1 salinity levels, respectively. Collectively, incorporating Si and K with standard fertilizer demonstrated synergistic effects, to mitigate the adverse impacts of salt stress through up-regulating root-shoot morphological traits, physio-biochemical attributes and fruit yield of bell pepper.