You don't actually have to have a green cert. You can enter into a long term lease to someone who does! (The rental income can also be tax free).
There are 2 different approaches to this;
1. Agricultural relief (which is what you're looking at), and
2. Business relief
A farm is a business, so normal business relief applies in the same way as the inheritance of any other business. It's not as generous, but works in cases where agriculture relief doesn't. The main difference is that only business assets are relieved, so the farm house for example isn't included.
There are also restrictions with agriculture relief around the value having to make up a certain percentage of your total assets after inheritance so a bit of planning may be required (it's not unheard of for someone inheriting a farm to have their family home transferred into spouses sole name for example). Business relief can also work in some of those scenarios.
Talk to a good accountant that deals with a lot of agriculture, and they'll be able to advise. A busy accountant in a farming area is dealing with these transfers every year.