How does grading improve the price I get and who sets the standards?

Grading lifts price because a sorted, uniform lot is worth more to a buyer than a mixed heap where good and bad are jumbled together. When you grade, your best produce is sold as a top grade at a top price instead of being averaged down by the poor pieces. Standards come from a few places. Agmark is the government quality certification for many agricultural commodities, with defined grades, and an Agmark grade can help in some markets and for some buyers. Beyond Agmark, individual buyers, exporters, processors and large retailers set their own size, colour and quality specifications, and meeting those exactly is what gets you the premium and repeat business. Mandis also have informal grade expectations. The practical approach is to find out what your specific buyer or market wants, grade to that, and keep it consistent so they trust your lots. Even simple size grading usually pays. Verify the relevant grade standard, whether Agmark certification helps for your crop, and your buyer's exact specification with the buyer, mandi or your local marketing or horticulture office.