You can’t wipe the grin off my face at the moment because one of my most daring experiments has reaped massive dividends: a tripling of our topsoil in three years.

Three years ago, almost half of our pastures were destroyed by the root-eating red-headed cockchafer.

Red-headed cockchafer grubs

These rotten grubs turned paddock 4 into a fluffy mix of topsoil and the desiccated remains of our ryegrass just ahead of Spring. It was devastating. You can’t control them with sprays because they stay too far down in the soil to be affected. The only alternatives are to resow and hope they won’t come back or physically squash them with cultivation and then resow and hope they don’t come back. The experts said two cockchafers per shovelful of soil equated to an infestation and paddock 4 had up to 50.

I became desperately worried as more and more paddocks succumbed. I started digging holes all over the farm trying to work out what would be hit next and looking for a cause in the hope of finding a solution. I failed in that quest but the exercise was worthwhile because the grubs taught me an incredibly valuable lesson. The pastures that suffered the most had relatively shallow topsoils over a hard clay pan.

Paddock 4 had about 12 to 15 cm of sandy loam over the moderately sodic clay. I decided to turn the expense of recultivation into an investment and had the soils deep-ripped and dressed with soil-conditioning gypsum in an attempt to keep them open.

Paddock 4 was sown with oats because they provide quick feed to fill the gap created by the grubs and their long roots are relatively cockchafer-resistant. After the oats were taken off in late spring, we planted the paddock with a summer brassica crop, which again has deep roots.

It was clearly time for some very expert help and we engaged independent agronomist Greg Forster, who worked out the nutrients, trace elements and lime needed to allow the soil to function at its best. We have since ploughed in the remains of a brassica crop, too.

Then, this week, scientists arrived to take metre-deep cores for analysis as part of the Victorian Soil Carbon Project. I was stunned. Too stunned even to remember to take a photo but that 12cm topsoil was now more like 45cm deep. “Lots of farmers would give their right arms to have soil like that,” remarked the supervisor.

I can’t believe it. I’m blown away and ever so slightly grateful to the red-headed cockchafer (though don’t think that’s an invitation to come back, you nasty little blighters).