Plant oats. Lots of horses need something palatable that is less high energy than grass or hay. Oat straw in small bales goes like hot cakes for laminitics and ponies. And you can sell the oats too, either as is, or bruised as animal feed. And it copes better with the UK climates than other cereals.
I am planning to plant some once I get the kit, have the plough so far.