Since last year, we’ve doubled the area under cultivation in our nursery. It’s still a really small nursery, but from tentative tinkering in a few beds two years ago, we’re building our confidence and expanding across the whole of one former-paddock-for-alpacas. As we grow, we’re watching the soil change.
There’s a lot we can observe just from our everyday interactions with the plants and the soil.
For example, we know that as you move down the slight slope the nursery sits on, there’s an increasing chance of the soil becoming waterlogged. On soggy days we can feel the water in the soil underfoot and even see it puddling sometimes. This is the area where we’ve put in over 200 willow cuttings this winter, in hope that they’ll help to buffer the wetness and improve soil structure, whilst also providing a wind break, and, in a few years’ time, woodchip.
Last week I was transplanting walnuts into one of our newly formed beds. We took a somewhat unconventional approach to making these beds. We shallow rotovated last summertime to kill off the grass, and then piled on a really thick layer of woodchip to stop the grass coming back and to start the process of composting organic matter into the soil. As I dug through the woodchip layer to plant my first walnut, I was horrified to see that what passed for soil here was almost solid clay, and smelly blue grey clay at that. Yuck. Not what I’ve gotten used to in our more established beds. Why was the soil right here so bad? What had I done wrong?
Of course there can be a lot of natural variation in the soil – or historical human created differences in the soil – even over really small distances. So perhaps it wasn’t my fault, but just a natural or historical anomaly. Hmmm. But this corner of the plot would probably have seen more tractor action than the rest, whilst we were rotovating last summer, because of the way we’d had to turn, and then back up in a tight space. Maybe it was extra compacted due to that tractoring, the soil structure squashed to nothing by the weight of the vehicle.
Back in the summer, we had sowed a mustard green manure mix straight into the woodchip, to help bring life back to the soil after the rotovating. In most beds the mustard thrived, but right where I was planting walnuts was one of those patches where the green manure had been eaten off by rabbits early on, so there had been nothing growing in the woodchip for months and months. Out of curiosity, I dug another hole at the other end of the bed, where the green manure had done much better. The soil at this end, whilst still heavy clay, was not not blue grey at all. It crumbled a bit. It didn’t smell bad. There were roots. There was life. Wow. Looks like green manures made even more difference than I thought they could.
I’m well aware that this anecdotal observation doesn’t prove anything. Any of those three factors, or dozens more, could account for all or part of what I saw, felt and smelled.
However, whilst this was a particularly dramatic comparison, my experience across the tree nursery is fairly consistent. The bed where we left our walnut rootstock undisturbed and undersown with yellow trefoil for two years has the most beautiful crumbly soil of the whole plot. The feel, smell and look of the soil over the beds has improved as the woodchip rots down, the fungi move in, the shelterbelts grow up, we add compost, and most of all, when we grow green manures. In the odd spots where green manure has failed to germinate or we’ve foolishly gone ahead and dug up plants when the wet soil structure wasn’t up to it, we can see we made a mistake when we look to the soil.
Science backs up the hunch that living plants make all the difference to living soil. It’s around plants’ roots where soil life really gets going, through complex exchanges of energy and nutrients. This is where soil structure is built and soil food chains begin. Plants also protect the soil from damage by wind, rain and sunlight, and give themselves back to the soil when they die, as composting organic matter.
Since we started the nursery, we’ve been carrying out some simple soil tests each spring and autumn, with the help of the SoilMentor app. The tests are practical and farmer friendly; they include counting worms and measuring rooting depth. They also help to give us some relatively quantitative data to track what’s happening over time, and to make comparisons across the different beds that we started working at different times.
Our tests seem to show that with each set of beds we made, we started with a ‘pan’ – a hard compacted layer – in the soil about 10cm down. Sadly, we probably created this ourselves through rotovating. However, over time, this pan seems to move downwards and loosen up, so that after two years of woodchip, green manures and working only by hand, it’s almost disappeared. Over the last two years, our soil has become on average deeper, plays host to more worms, and is more alive around the plant roots.
I’m not saying we’ve got it all figured out, not by a long way. I want to be using more green manures, both in diversity of species and in area of coverage. I’m concerned about how lifting nursery plants each winter will impact the soil, keen to find out how we can better alleviate any damage, and curious whether we’ve built enough rest time into our rotation plan. I’d love to see even more fungi popping up next autumn, and I’m sure we could build the level of organic matter in the soil a long way still.
But just now I’m thinking that whilst the yucky patch of smelly clay soil demonstrates something gone wrong, a mistake made, it also demonstrates what we’re getting mostly right across the rest of the nursery beds.
Jessie Marcham
