We introduce a novel form of experimental knowledge that is the result of institutionally structured communication practices between farmers and university- and local community-based agronomists (agricultural extension specialists). This form of knowledge is exemplified in these communities’ uses of the concept of grower standard. Grower standard is a widely used but seldom discussed benchmark concept underpinning protocols used within agricultural experiments. It is not a one-size-fits-all standard but the product of local and active interactions between farmers and agricultural extension specialists. (...) Grower standard is in some ways similar to more familiar epistemic objects discussed in philosophy of experiment, such as controls or background conditions. However, we argue that grower standard is epistemically novel, due to how knowledge arising from it is coproduced by farmers and agricultural extension specialists. Further, in the United States, this knowledge coproduction is institutionally structured by federal legislature dating back to the 19th century. We use our analysis of grower standard to focus a discussion of the positionality of the coproducers as well as the epistemic products of this form of knowledge coproduction, and we explore the role extension work plays in shaping agricultural science more broadly. (shrink)