The joint venture in which Fane Valley takes a 50% share in Drummonds came into effect this week having been cleared by the Competition and Consumer Protection Commission.
The venture was originally announced at the end of November and will mean that the combined businesses will have a strong presence across the northeastern part of the island of Ireland.
Fane Valley is a farmer-owned co-op, and is headquartered in Moira, Co Antrim.
It has a network of farm supplies stores across Northern Ireland and a milling business that supplies the north and border counties.
It also has a portfolio of speciality meat businesses and the White’s Oats business.
Drummonds’ core business is the purchase and marketing of a wide range of grain types and it has a substantial seeds business in Drogheda, Co Louth, as well as a network of stores.
Fane Valley chief executive Trevor Lockhart said: “There is a very compelling strategic rationale for this joint venture and many synergies to be realised.”