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

Rice2is the most consumed staple food in the world, but it is produced with barriers like low productivity, environmental factors like climate change, over-application of nitrogenous fertilizer, losses of soil fertility, and more water demand. This study revealed the effects of water management strategies, biochar application levels, and nitrogen fertilization rates on the growth, physiology, yield, water productivity, and nitrogen use efficiency of rice. A factorial experiment was conducted under a controlled environment, with soil water potential levels (0, -15kPa, and 30kPa), biochar application levels (0, 10, and 20 t ha-1), and nitrogen applications (0, 30, 45, and 60 kg ha-1). Results showed that plant growth and yield parameters were highest under saturation level (when 0kPa was followed). At the same time, -15kPa achieved comparable performance with significantly lower water usage, reducing it by 29.33% relative to saturation level (0kPa). Biochar application of 20 t ha-1 notably enhanced plant height, dry matter accumulation, root development, chlorophyll content, and membrane stability across both irrigation methods, primarily through improved soil water retention and nutrient availability. Nitrogen fertilization at 60 kg ha-1 optimized growth and yield, though 45 kg ha-1 also provided strong performance with more efficient resource use. Biochar 20 t ha-1 combined with nitrogen 45 kg ha-1 significantly improved morphological and physiological traits. Integrating -15kPa soil water potential, nitrogen 45 kg ha 1 , and biochar 20 t ha-1 emerged as a sustainable strategy, improving water productivity and nitrogen use efficiency without compromising the yield. These findings provided practical insights into developing more sustainable rice cultivation practices suitable for future agricultural challenges.