In my Jewel of the Desert DW game, farming-type magic is pretty much exclusively the province of Kahina (druids and shaman.) Druids practice it by interacting directly with the "living" spirits of things actively moving in the material world: elementals, the spirits of trees* and the conceptual spirit/essence of what it means to be a given beast or plant. Shaman practice it by dealing with the "dead" spirits of the afterlife: the spirit of Owl or Desert Fox, for example, or the ghosts of creatures killed in a forest fire that still linger in the spirit world, etc. Druids quicken and invigorate living spirits, calling them to greater action. Shaman call on those abstract-idea/animal spirits to reach across the veil, or push the spirits of the unquiet dead to "pass on" and thus give their energy back into the cycle of life and death.
A village with Kahina aiding it (or a neighborhood within a larger town/city) will generally have healthier crops and vegetation and be overall more comfortable to live in. The Kahina are not centrally organized, but in general they try to make sure most areas have both one druid and one shaman (ideally, a pair of close friends or lifemates) as their skills tend to be complementary. In Ye Olden Dayse, every tribe needed some Kahina in it just to survive, as the Genie-Rajahs ruled the cities and the desert wastes outside Genie-Rajah control were not particularly hospitable to life (think Bedouin for these Nomad Tribes.) Modern-day Nomads benefit from trade with the City-Dwellers, but still prefer to have at least one Kahina among them (often several; sometimes, the position of Chief and Kahina is merged into a single role.)
*Which can slowly develop into the spirit of a forest, if the forest lasts long enough; many spirits are gestalt entities, simultaneously their own independent being and a collection of constituent spirits that have "been together" long enough to operate in unison. The party Druid has briefly interacted with the Spirit of All Winds, for example, which is an extremely powerful and old spirit, but one that doesn't really "think" about mortal-level concerns very much.
