Operating under a limited company, you would still have the exact same issues. They have restricted APR and BPR to £1 million. If you have a farm worth £5 million, you will now need to pay IHT of £800k, whereas before it was nil.
Whether you are left shares in a limited company or a partnership share and/or the land directly, you still need to find that £800k. The business structure has absolutely NO impact on the IHT payable, so comments such as "just operate like other businesses" are irrelevant.
This Budget has actually had the same impact for all businesses.
The main differential is that in terms of other businesses, if there profits each year are saying £1 million perhaps a manufacturing business, then the business may be worth saying £5 million so a multiple of 5. For a farm, the return on capital employed is far far less, so it might only be say 1/2% (if they are even profitable) meaning the profits might be £50k/£100k and the business is still worth £5 million.
Previously the manufacturing business shares could also be left IHT free so they will now also have an IHT liability. The big big difference though is that the farmer is much less profitable to try and find that money or even borrow it.
But actually these changes are going to impact ALL businesses, not just farmers albeit it is probably the farmers who will struggle the most to pay the tax.