Organic agriculture faces unique challenges of nitrogen management and weed control. On field precision experimentation (OFPE) is an adaptive management metho- dology of field-scale experiments which helps organic farmers understand within-field variation in crop production. Precision agriculture technology is used to design, imple- ment, and record OFPE results. The aspirations of OFPE in organic grain farm settings are to optimize nitrogen inputs from green manure cover crops, to minimize weed im- pacts, and maximize crop yield, quality, and profits from cash crops. Field scale experi- ments have been implemented on multiple sites across Montana and Manitoba to test seeding rates for optimum nitrogen management, weed control, and yield in organi- cally managed pea, wheat, and hemp rotations. Results from experiments using varied seeding rates, indicate that optimized variable rates outcompete farmer-chosen single field rates and can increase farmer profits.