Marine Macroalgae as Natural Biostimulants for improving growth, yield and functional quality of Capsicum (Capsicum annuum L.) under polyhouse condition

Abstract

The growing emphasis on sustainable agriculture has increased interest in seaweed-based biostimulants as environmentally friendly alternatives to synthetic agrochemicals. A study was conducted under polyhouse conditions at SRM College of Agricultural Sciences, SRMIST, Chengalpattu, Tamil Nadu, India, during the rabi season of 2025–2026 to evaluate the influence of marine macroalgae biostimulants on the growth, yield, and functional quality of capsicum (Capsicum annuum L.). The experiment was laid out in a Completely Randomized Design (CRD) with ten treatments and three replications, comprising foliar applications of Ascophyllum nodosum, Kappaphycus alvarezii, and Gracilaria edulis at 2.5, 5.0, and 7.5% concentrations, along with an untreated control. The results indicated significant improvements in vegetative growth, flowering, yield, and fruit quality due to seaweed biostimulant application. Among the treatments, Ascophyllum nodosum at 5.0% (T₃) produced the highest plant height (127.0 cm), number of leaves (89.3 plant⁻¹), fruits per plant (31.0), average fruit weight (198.6 g), and fruit yield (19.2 kg m⁻²). It also promoted earlier flowering and enhanced SPAD chlorophyll values. Quality attributes, including ascorbic acid and capsanthin content, were highest under T₃, whereas total phenol content was maximized in T₄ (Ascophyllum nodosum at 7.5%). The study demonstrates that foliar application of Ascophyllum nodosum at 5.0% is an effective and sustainable strategy for improving capsicum productivity and fruit quality under polyhouse condition.