Integrated nutrient management and physiological responses in Kalmegh (Andrographis paniculata): A comprehensive review

Abstract

Integrated nutrient management (INM) is a key approach for maintaining soil fertility, increasing crop productivity, and promoting environmental safety in medicinal plant cultivation. Kalmegh (Andrographis paniculata Burm. f. Wall. ex Nees), a medicinal herb valued for its bioactive compound andrographolide, demonstrates marked physiological sensitivity to soil nutrient availability. This review synthesizes research from global and Indian contexts regarding the effects of organic manures, inorganic fertilizers, and biofertilizers, both individually and in combination, on the growth, yield, nutrient uptake, quality, and economic outcomes of Kalmegh cultivation. The combined application of organic and inorganic nutrient sources significantly increases plant height, leaf area, branching, and biomass by enhancing photosynthetic activity and root development. The use of farmyard manure, vermicompost, and balanced nitrogen, phosphorus, and potassium (NPK) fertilization improves the rhizosphere environment by enhancing soil physicochemical and biological properties, nutrient-use efficiency, and microbial enzymatic activity. Physiological studies reveal that organic-inorganic integration enhances chlorophyll content, stomatal conductance, and nutrient assimilation, resulting in greater accumulation of andrographolide and other secondary metabolites. Biofertilizers, including Azospirillum, Azotobacter, Trichoderma harzianum, and vesicular-arbuscular mycorrhiza (VAM), further enhance phosphorus uptake and influence hormonal and enzymatic processes related to plant growth and stress tolerance. Economic analyses consistently demonstrate higher net returns and benefit-cost ratios for integrated nutrient management compared to the exclusive use of either organic or inorganic inputs. This review highlights the diverse physiological mechanisms and sustainability advantages of integrated nutrient management in Kalmegh cultivation. INM contributes to maintaining soil health, maximizing herbage yield, and improving phytochemical quality. Future research should prioritize standardizing nutrient combinations, investigating microbial consortia, and incorporating nanofertilizers and precision nutrient management technologies to support sustainable and high-quality production of Andrographis paniculata.