When farmers adopt a food safety program, they have to buy the inputs. Buying inputs is one thing that falls under the definition of "post-farm". Ultimately, the commodities that farmers sell are a result of agricultural production for which they purchased certain inputs.
Food safety programs ensure that the products that farmers buy to use in agricultural production meet food safety objectives. That ensures that the end product is of very high quality.
That is one of several examples. You have the inputs suppliers. It is the same thing at the distribution stage. When a farmer's fruits and vegetables leave the farm, they will be subject to the same process in order to get into the supply chain.
The aim is to have farm-to-table food safety systems, or traceability systems, that allow the commodity to be followed at all stages and that provide assurance that the product is of very high quality when it reaches the home.