Inoculation Day

Last week we talked about using mycorrhizal fungi to improve the health of fruit trees. The fungi are best placed between three and twelve inches below the surface, and either in contact with the roots, or close enough that the roots will find them quickly. So how best to get them there?

When I asked Tammy Kovar how her workers accomplish this for contract jobs, she said they use an auger to bore circular holes, an inch or two in diameter, and fill them with a mix of fungi and soil. That's fine, but augering is not a low-effort pastime. And there's some damage done to the roots, perhaps inconsequential, but I'd prefer not to damage the roots at all if possible.

MRFC Secretary Josh Starry invented a simple but ingenious device to get the job done, as long as there's a good water supply available. A shaft of PVC pipe shoots a jet of water out the end, focused enough to excavate a narrow hole in the soil without actually cutting anything. A valve next to the handle controls the flow, and a bit of experimentation yields a flow rate that works without spewing excess water all over the place.

Here it is in action near one of my citrus trees.

The hole is about 1½ inches across, and as deep as one wants.

Meanwhile, I mixed Tammy's mycorrhizal product with some dry biochar, about 1 part to 4.

Here I am dropping in the mix up to about 3 inches from the surface. I filled the rest with topsoil and Josh watered it all in.

Maybe our efforts will get an extra year or two of fruit out of the struggling citrus, which would be well worth it. The process is fast and easy, and some afternoon we'll do the smaller fruit trees. 

With so many variables in play, it's mighty hard to tell which pampering of our trees has an impact and which is just a waste of time and money. But methods that enrich the ecology rank high in my book.