In Stephen May v HMRC [2018] TC6928 the First Tier Tribunal (FTT) held that a horizontal silo was plant for capital allowance purposes. 

A person who is engaged in Qualifying activities is able to claim plant and machinery allowances when they incur qualifying expenditure.

A farmer installed a horizontal silo to store, dry and maintain his grain.

The issue was whether the whole silo was plant subject to capital allowances, or if it was a building. In the latter case, the silo would not attract a capital allowance though some of the equipment would.

The FTT held that the silo worked as a single unit and was a silo provided for temporary storage, so it attracted capital allowances as plant.

Useful guides:

Plant & Machinery (self-employed) allowances
A guide to what capital allowances the self-employed can claim on plant, machinery and equipment.

Farmers: what expenses can I claim?
What expenses can farmers claim for tax purposes? Are there special tax and accounting rules for farmers? What are the rules for VAT for farmers? This guides answers these questions and more.

Farming: capital allowances 
Our guide to capital allowances specific to the farming industry including pig farming.

Structures & buildings allowance (SBA)
A detailed guide to the new structures and buildings allowance introduced in October 2018.

External links:

Stephen May v HMRC [2018] TC6928.