Greywater can be used to supplement your farms water supply. It can be used to water garden plants (but not vegetables), wash-machinery and vehicles and keep dust down around the house.
Take care when using it though. Make sure farm animals and pets don’t drink it and that it doesn’t run into creeks or other waterways. Unless you have a proper treatment facility you should not store greywater. There are also biodegradable washing products that make your greywater safer to use.