At openstreetmap-carto - the standard style on osm.org - a change has been merged (https://github.com/gravitystorm/openstreetmap-carto/pull/2554) to drop rendering of landuse=farm. There was overall consensus that this tag is deprecated and its usage steadily declined over the last years, but there are still around 340 000 uses. See https://taginfo.openstreetmap.org/tags/landuse=farm and http://taghistory.raifer.tech/ for details.
This change will make it into the next release, but there is no release date yet. You might want to change cases of landuse=farm in your area to either landuse=farmland or landuse=farmyard before that. Please don’t do any automatic re-tagging though. After the release empty spots will make it easier to clean up the remaining uses of this tag.