The event, organised by Linking Environment & Farming (LEAF), is an opportunity for the industry to show the public how they produce the food they eat and how the countryside is managed.
Last year, 184,000 visitors attended events on 420 farms. LEAF is calling on even more farms to take part this year, which has been themed "Discover Life on Britain's Farms".
Chief executive Caroline Drummond said: "We want farmers to help us build on previous success. For most people this is one day in the year when visitors can discover what really happens on a farm. For farmers themselves, LEAF research shows that 80 per cent of participants last year saw it as a real business benefit."
LEAF offers farmers free support in many different ways to help them run a successful event, whatever their farm's size. Support includes:
Workshops - free to attend and taking place across the UK in March. Farmers and growers will be able to meet previous participants and to learn from their experiences.
Resource pack - contains publicity material, suggested activities and health and safety guidance.
Website - farmers can register their event, watch the online workshop video and find out more about the campaign at www.farmsunday.org.