Journal ArticleThe cost of investing in agricultural technologies and their opportunity costs are key drivers of technology adoption by farmers. Integration of many technologies in the production of a given crop is commonly practiced by many farmers, yet most studies investigate profitability of single rather than combinations of technologies. The objective of this paper was to investigate economic benefits of including legume in rice based cropping system in a major rice producing region of Morogoro in Tanzania. Data was collected by interviewing farmers on planting methods, analyzed using descriptive statistics, gross margin and partial budgeting. Results show that rice is an important crop in smallholder farming systems, benefit cost ratio was higher (2.913) when rice was rotated with legumes and was low (1.381) without rotating with legumes. This study shows that current practices of producing rice is unprofitable with average yields of 180kg/ha in the nearly season compared to the last five season of 405kg/ha. Partial budgeting and cost benefit analysis revealed that introduction of legumes is beneficial and sustainable leading to increased yield and income by more than 100%. Thus the inclusion of legumes into rice cropping system offer an ideal option for maximizing returns in smallholder rice based system.