A Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Agricultural Systems and Engineering

Thesis (M. Sc.) - Asian Institute of Technology, 2025

Drought is a major factor that hampers agricultural development worldwide. Stevia (Stevia rebaudiana), recognized as a natural no-calorie sweetener of significant therapeutic and economic value, has been considered globally as an alternative to synthetic sweeteners. Drought stress, however, affects its growth and yield profoundly and influences plant growth, leaf yield, and physiological characteristics. This study investigated the efficacy of silicon and nano-silicon in mitigating the impacts of drought stress in stevia. Two independent pot experiments were conducted under three soil moisture levels (45, 65, 85% FC) using completely randomized design. For Experiment 1(soil application of Si), four doses of Si (in form of monosilicic acid containing 20% Si) applied were 20, 40, 60 kg ha-1 along with the control. For Experiment 2( Foliar application of n-Si), four concentrations of n-Si applied were 50ppm, 100ppm, 150ppm along with the control. Results showed that a reduction in root dry matter 32-54% and 27-50% was observed in Experiment 1 and Experiment 2, at 40%FC compared to 85% FC throughout doses. Soil application of Si significantly increased plant height, leaf fresh and dry weight, water productivity and leaf relative water content under 85% FC at 60 kg ha-1 Si in Experiment 1. Among different foliar application of n-Si, 100ppm was effective resulting in plant height, leaf fresh and dry weight, and leaf relative water content. Soil application of Si at 60 kg ha-1 and foliar application of n-Si at 100ppm is recommended for stevia cultivation under drought conditions.