Using iis is definitively a good choice if the solver you are using has that option.

Quick suggestion, have you tried dropping constraints to figure out which one is not being satisfied? (I assume it's infeasibility not unbound problem). Constraints like Demand Fulfillment, Minimum distribution and Nutrient requirements might have data that produce this infeasibility. Without them, a trivial solution would be possible, right?

Any solver output or data for the problem?