Walmart has also struck up a key partnership with United Suppliers, a network of more than 700 agricultural retailers in 20 states, which offers a program called Sustain. The retailers' field staff are being trained to help farmers better manage and track their inputs, and United Suppliers has promised Walmart that it will reduce fertilizer on 10 million acres of cropland by 2020. That work alone would get Walmart nearly halfway to its emission reduction goal.