Custom Trailers for Farming
Along with regular farming trailers that are provided with Editor (trailer_cultivator, trailer_harvester, and trailer_planter), you are able to create your own custom mods of farming trailers and use them on your maps.
Their ceation is similar to the creation of regular non-farming trailers, you just need to add some properties to the XML of the class of the trailer.
For details, see Farming Trailers in the Truck Modding section.