The present study evaluated the sustainability of yield and value in blackgram cultivation by adopting improved production technologies through frontline demonstrations. These were implemented as sole and rice fallow crop cultivation in Tamil Nadu, India, to reduce yield gaps at farmers' fields. The scientific study was conducted in 2020-2021 with 295 demonstrations (118 hectares) using cluster village methodology to examine the effects of extension gap, technology gap and technology index on yield and economics by demonstrating improved technologies. These include mechanized sowing, use of disease-resistant varieties, integrated pest and weed management, seed treatment, crop nutrient boosters and mechanized harvesting. Yield enhancement of 51.55 % was recorded in a demonstrated package of technologies over farmers' practices, primarily due to the adoption of Yellow Mosaic Virus-resistant varieties, effective weed management strategies, and foliar sprays like TNAU pulse wonder to boost crop growth. The average extension gap (2.89 q/ha), technology gap (0.87 q/ha) and technology index of demonstrations (11.01 %) were documented, which are mainly due to efforts of multidisciplinary scientists’ field visits and farm advisories. A study reported higher weed control efficiency (48–76 %) in demo plots, enhancing demon yield than in control plots. Compared to farmers' plots (Rs. 37075/ha), average net returns in demonstrations were higher at Rs. 66732/ha. The study also disclosed an additional net return (Rs.29657/hectare) with an incremental BCR of 19.95, indicating a significant increase in profitability relative to the investment. The consistently greater Sustainability Yield Index (0.61 to 0.99) and Sustainability Value Index (0.88 to 0.93) in demo plots highlight improved stability and economic value of yields compared to farmer's plots. The latest package of technologies in blackgram paved the way for sustained yield under normal conditions, which are defined as fields with adequate moisture and timely sowing and rice fallow conditions. These advancements improved farmers’ livelihoods by increasing net returns and ensuring more stable and predictable yields.