That is broadly correct. One thing to say is that in the uplands there is almost no mixed farming. In fact, it would be very hard for mixed farming to be established in the uplands, which are very unsuitable on the whole for arable. In the lowlands, if we were to reintroduce mixed farming, at the microlevel that could be a very good thing by comparison to the arable deserts of East Anglia, but we would see a major decline in total yield. There is very little research on what that decline would be, but everyone can more or less accept that we will see that decline.
The global conundrum we are in is that roughly half the global population is dependent on NPK, to put it crudely, and certainly on nitrogen and other artificial fertilisers. If we were to take those out of the system, we would have mass starvation—huge numbers of people would die. However, we are aware that applications of N, P and K and others are causing global disaster: they contribute significantly to climate breakdown, soil loss, downstream pollution, air pollution and a whole load of other issues. We cannot live with it and cannot live without it. We are in an astonishing and very difficult conundrum. If we were to switch—as the Soil Association recommends and as my instincts would tell us to do—to mixed rotation or organic farming, we would not be able to produce enough food. It is as simple as that.
How do we get out of that conundrum? I see some hope in factory-produced food—microbial protein and cultured meat. That could be the only way of reconciling environmental needs of future generations and the rest of life on Earth with the need to feed people alive today and in future. We need to find ways of feeding the planet without devouring it. That could be the way.