<p>Wheat productivity in alluvial plains of Bihar is increasingly constrained by conventional tillage (CT) practices that degrade soil quality and reduce resource-use efficiency. Conservation agriculture (CA)–based crop establishment offers a potential pathway to restore soil health while improving productivity and farm profitability. A two-year field study (2021–22 and 2022–23) evaluated four wheat establishment scenarios differing in sowing method and residue retention, ranging from farmers’ broadcasting practice with low residue input to Happy Seeder–based sowing with higher residue retention. Wheat yield, soil organic carbon, water-stable aggregates, available nutrients, and economic returns were assessed. The Happy Seeder with 3 t ha⁻¹ residue retention consistently produced the highest grain yield, recording 33–35% increases over farmers’ practice across both seasons. This system also enhanced post-harvest soil organic carbon by 12–17% and improved soil aggregation, indicating better soil structural stability. Availability of soil N, P, and K was significantly higher under residue-retained CA-systems. Economic analysis showed that net returns increasing by 48–50% compared with conventional practice. The results demonstrate that Happy Seeder–based wheat establishment with adequate residue retention (3 t ha⁻¹) substantially improves productivity, profitability, and soil sustainability. Its adoption provides a resource-efficient and climate-resilient option for sustainable wheat intensification in Bihar’s alluvial agro-ecosystems.</p>