Earthworks update.

By Andy Williams.

It hasn’t rained. It hasn’t rained in a very long time. We’ve had one brief shower since early May, roughly eight weeks ago. Now normally I’d be loving the opportunity to get so much done out on the croft, but we have a lot of bare earth baking in the sun, waiting for rain to sprout the meadow seed mix we’ve spread everywhere. The existing pasture is coping with the dry conditions well, but everything we’ve planted is struggling. In late winter we planted well over 700 bare root trees. They’ve done well, but a few weeks ago trees that were healthy started suddenly dying, When we pulled back the mulch around the base of a random tree, we found that the soil had shrunk so badly that it had left a huge crack that took two spadefuls of soil to fill. Every tree was like this, apart from the willow.

We’ve had to barrow soil to every tree and shrub we’ve planted, remove the stones holding the mulch down, remove the mulches, fill the trenches, reverse the process, then water them all. It’s taken some time. While we were at it, we added a scoop of slow release fertiliser to the fill around each tree. It’s not something we plan on doing in the long term but these trees have had a very rough start and at this point their survival has become the priority. Under the circumstances, I’m comfortable bending the rules occasionally to accelerate the establishment of the system. This is extreme weather, and once established the systems should be resilient enough to cope with such events easily, but only if we can get it there. The earthwork systems we’ve installed should make droughts like these practically irrelevant, but only after they’ve actually had some rainfall to harvest. Is it any wonder I’m frustrated?

One silver lining to it being so dry for so long is we’ve been able to see some of the wildlife benefits of the earthworks. Even when they’re bone dry, hard baked soil with no plant cover, the birds love the earthworks. The crest of each swale berm has a healthy sprinkling of bird droppings. Many bird species won’t search for food very far from a perch, and for some species fence posts just won’t cut it. Instead of an unbroken field of grasses and scrubby plants it’s now got high and low points, sheltered and exposed spots. The diversity of birds in the field has already started to increase as a result, and now occasionally at dusk we see a barn owl hunting. I often find evidence of bird kills on the very highest points of the berms, though I couldn’t say what species is doing it. The berms will eventually be planted to productive tree and shrub species, so will really benefit from the enrichment.

This week, after much sulking  thought, I worked out I could just about get a hose to the lowest earthwork. This is a stepped pond, with a curved berm behind it, shaped to catch and reflect the southern sun. It has a contour ditch to one side that collects overland flow and directs it into the pond, and should the pond fill completely during a major rain event the ditch will act as a level sill spillway so the berm won’t blow out from the weight of the water. There are several level platforms cut into the sides of the pond, the largest being the highest, just a couple of inches lower than the height of the level sill spillway.  In the event of the pond becoming overfull, first it’ll soak the top platform, then start to soak into the berm. Only then will the spillway kick in, so the water can’t get any deeper. It means that should we choose to, we can release water from further up in the landscape, flood the pond and soak the berm to water the whole area. The back of the berm has been planted with willow cuttings and then the whole area has been seeded with a meadow flower mix. It’s a small pond by agricultural standards, but even after months without rain it has a couple of feet of water in the bottom. Once it’s greened out the plant roots will knit the soil together and it’ll be a source of permanent water as well as being one of the most sheltered places on the croft. When the willow on the back of the berm has grown, it’ll be woven together to make a dense screen that will really shelter the whole earthwork from the wind. I dug a lot of big stone from this pond, so I’d planned on adding them to the berm to act as heat stores. If you’re going to add piles of stones to an earthwork though, you might as well make them comfortable to sit on. I’m going to rebuild the first of the stone seats I put together, but it’s hardly a priority.

With the hose just able to reach the end of the water collection ditch I was able to finally test it all. You can spend all day double checking the levels, but until you see water in it there’s always a niggling doubt in the back of the mind. This is the only truly finished part of the earthworks. By the time I’d finished this one, the sun had baked the soil so hard that trying to work it with spades is just brutal. I’ll post the other parts of the system as they become finished, because in the raw form they really don’t look like much. Have a look at these two photos for the contrast.

I don’t expect the pond to be full very often, and almost never during summer. If it’ll hold a couple of feet of water when it hasn’t rained in months however I’m sure it’ll be significantly higher for most of the year. Most new ponds seep a lot more water than they do when they’re older, clay particles washed into the pond are drawn into the tiny seep spaces and partially block them, making the pond to hold water better. You can buy preparations to give a pond a head start, or to fix a leaky pond. Other techniques use ducks to manure the water, because duck poo has particularly fine particles. We don’t have ducks yet but we do have clay. I’ve mixed up a tub of clay and water into the consistency of double cream. I’ve watered a third of it down and added it to the pond while it’s full. The pond already seeps very, very slowly, so any improvement should be significant. When the pond is full it’s over 8 feet deep in the middle. It’ll be interesting seeing what sort of depth it settles at. The next phase of the earthworks isn’t going to be built for at least a couple of years, but I’m so pleased by how this pond turned out that I’m really looking forward to it.