Given the plateau in arable crop yields over the past 30 years, it’s not surprising Adas launched its Yield Enhancement Network last year to remind farmers how important it is to try to boost production.

But when ideas currently being tested by Adas at their research centre in Boxworth, Cambridgeshire, include the improbable techniques of blowing air into soil to a depth of one meter before drilling a crop (to improve “root growth”) and erecting a polythene fence around a crop (to keep it cooler at night to reduce “respiration losses”) has the search for ways to improve arable yields reached crisis point?

Many British farmers blame the EU’s stubborn resistance to the introduction of GM crops as the primary reason why arable yields have barely risen since the 1980s. But wherever GM crops are grown in the world they have not proved a particular boon to crop yields. GM crops certainly have the potential to improve farm productivity (in the sense that crops need fewer workers and machines can cover more hectares), but that is more down to the use of glyphosate on growing crops being suitable for min-till techniques.

But with or without GM, will we ever return to the heady days of the post-war period when arable yields just kept on rising? From the 1950s, farmers of my father’s generation fully expected to add to their crop storage capacity every decade without expanding their farmed acreage. Even I, who started farming in the early 1980s, can remember the thrill of corn stores filled to the brim and having to fill my garage with 50t of barley in 1984, such was the general increase in my and every other British farmer’s average yield that year. (I have experienced no such surge in yields since.)

Of course, any farmer visiting Cereals in 2014 would have come away convinced that yields will keep edging up as they would have left convinced of the same thing by every Cereals event since its inception in 1979.

After all, look how much better that new variety of wheat resists septoria than any of the current varieties on the HGCA Recommended List?

Who would doubt the advantage of a precision fertiliser spreader, informed by a satellite navigation system about whether to increase or decrease the P and K application rates across a field? And only a halfwit would question the benefit of a yield map drawn from a combine yield meter linked by satellite to a seed drill to alter seed density gauged by yield potential.

But after 30 years of investment in such an endless series of “improvements”, the result is very nearly no improvement in crop yields. Once upon a time, Adas, as a fully government-funded research and free advice service to farmers, oversaw plant breeding and the development of new pesticides and the resultant double digit increase in crop yields decade after decade. Nowadays, a partially privatised Adas is reduced to inserting reflective tape between crop rows and installing trickle irrigation to provide more water to crops, perfectly well aware that such approaches are unlikely ever to be practical or cost-effective at farm level.

Isoproturon is gone forever, neonicotinoids are banned in the EU for at least two years, and there are many more restrictions on the use of agrichemicals heading our way. Rather than increase our yields, could we instead turn out to be a generation of farmers staring at the unthinkable: increasingly unused capacity in grain stores built by our fathers?

Stephen Carr farms an 800ha sheep, arable and beef farm on the South Downs near Eastbourne in partnership with his wife Fizz. Part of the farm is converted to organic status and subject to a High Level Stewardship Agreement.