I'm working on a medieval world in which homo sapiens domesticated several other species of intelligent hominids during their prehistory, at first enslaving them to take advantage of specific desirable adaptions, and then breeding them to further specialize them for a social role. This combination of natural selection and breeding has, over a suitably vast time scale, produced a society of related but physically and mentally distinct species - a biological caste system.*
I'd like one of these species to be ideal farmers. They would have probably evolved farming practices early in their evolutionary history, like certain real-world animals. Later, after inventing agriculture proper, they would have been conquered and bred into a herd of docile farmers and laborers for their human masters.
By the end of this, they would need to be highly adapted to growing staple crops, petty labor, taking orders, and really not much else. Aesthetically, it would be a plus if these adaptions also led naturally to interesting visual differences, but I can already work cosmetic changes in pretty easily so that isn't my first priority.
- What physical and mental adaptions could an intelligent hominid evolve that would make more ideally suited to farming grain staples?
A very random hodge-podge of example ideas might include adaptions that allow them to sense the weather, better fertilize plants, do tiring and repetitive labor, cooperate peacefully in groups, adapt their own actions and biological rhythms to seasons of growth, somehow encourage plant growth or prevent disease, etc. etc. There are probably other interesting adaptions that I'm unaware of to be found in nature, and of course, I welcome any plausible original idea.
As a final note, while I'd like to keep this hominid "human-ish", at least physically, site users should consider themselves welcome to push hard at the boundaries of that condition if it makes their answer more interesting. It's easier for me to scale an answer back than to scale it forward.