OPTIMIZING UREA APPLICATION FOR ENHANCED GROWTH AND STEVIOL GLYCOSIDE BUILDUP IN STEVIA

Abstract

Stevia rebaudiana is a high-value natural sweetener crop known for its steviol glycosides, primarily stevioside and rebaudioside A. Nitrogen is a precarious nutrient influencing both vegetative growth and secondary metabolite production in stevia. This study aimed to optimize urea (a widely used nitrogen source) application levels for maximizing stevia biomass and glycoside accumulation. A field experiment was piloted using a randomized complete block design (RCBD) with five nitrogen levels: 0-160 kg N ha⁻¹ with difference of 40 kg, designated as T1 to T5. Results exhibited that all growth parameters i.e., plant height, branches, leaf area and dry biomass, improved significantly with enchanting nitrogen rates up to 120 kg N ha⁻¹. The same trend was observed for leaf yield per plant and per hectare, as well as dry leaf yield. Stevioside and rebaudioside A contents, along with total glycoside yield, also peaked at 120 kg N ha⁻¹. Although the highest nitrogen dose (160 kg N ha⁻¹) produced similar results, it did not significantly outperform the 120 kg level, indicating a point of diminishing returns. Soil analysis confirmed improved organic matter and nitrogen availability without adverse effects on pH or electrical conductivity. These findings suggest that 120 kg N ha⁻¹ is the optimum dose for achieving maximum productivity and steviol glycoside yield under current field conditions. The study provides evidence-based nitrogen management strategies to enhance the economic and functional value of stevia cultivation. Further multi-location trials are recommended to validate these findings across diverse agro-ecological zones.