Enhancing soil health and productivity of Lycopersicon esculentum Mill. using Sargassum johnstonii Setchell & Gardner as a soil conditioner and fertilizer

This study was aimed at developing a protocol for improving soil health using Sargassum johnstonii as a conditioner and fertilizer. Tomato (Lycopersicon esculentum) plants were raised on seaweed-amended soil in experimental fields of Department of Botany, University of Delhi, India. Soil was amended with granular (G) and powder (P) seaweed forms in the proportion of 12.5 % (G₁ and P₁), 25 % (G₂ and P₂), and 37.5 % (G₃ and P₃) (w/w). To compare the efficacy of seaweed fertilizer with a conventional organic fertilizer, a parallel series (positive control) was run with vermicompost (V) in the above-mentioned proportions. Unamended soil served as control (C). The nutrient status of S. johnstonii and vermicompost was analyzed prior to giving treatments. Physicochemical properties of the amended soils as well as growth, productivity, and biochemical constituents of tomato grown in soil with each treatment were analyzed. Higher concentration of granular form of seaweed (G₃) in the soil resulted in 144, 268, 122, 138, and 188 % increase in Na, K, Mg, Ca, and Zn, respectively. Seaweed-amended soil had higher porosity and water-holding capacity as compared to C. Tomato plants raised on seaweed (G₃ and P₃)-amended soil showed an increased overall growth, with earlier flowering and fruiting as compared to control plants. Plants raised on G₃-amended soil showed significantly higher levels of proteins (95 mg g⁻¹ FW) in leaves, and vitamin C (99.2 mg 100 g⁻¹) and lycopene (5.78 mg 100 g⁻¹) in fruits. The present study showed that S. johnstonii biomass has a high potential to condition and fertilize the soil for improved crop productivity.