"The price comes down! I often cringe when the media talk about a bad harvest in terms of volume. yes yields may be down, but guess what supply shortages means prices rise. Often the same "profit" will be gained room less produced."

The flaw in your argument is that in particular commodity crops such as wheat rape barley are now global markets. In the 60's yield down price up logic was valid. Now if your UK yield goes down it doesn't mean price goes up if weather has lead to big harvests in US Midwest, Australia or (historically) Ukraine. Look at the impact of the Russian invasion on wheat prices as an example - they shot up, but so did fertiliser prices.

Secondly commodity prices are subject to futures markets and speculation by investors with no physical product and so price is no longer a function of simple yield. Farmers are not experts in futures trading or hedging - although they have had to try to become so or face the consequences.