Re-raising vegetable beds
In a previous post I mentioned that the soil in our raised vegetable beds at Homeland looked “tired”. We had a very poor harvest this summer, a lot of weeds and grass creeping in and as a result we decided to redo these beds as proper no-dig beds.
Way back when – this must be more than 6 years ago – when we didn’t know about no-dig beds yet, most of these beds were filled with a mixture of garden soil and compost, which we got carted in by the truck load when we started off. I remember at that stage we could still get the trucks into our backyard to drop the sleepers, garden soil and compost right at the entrance to the vegetable patch. You won’t be able to do that now!
Creating the veg boxes ages ago. Wish it was that green now!
So we earmarked some beds for the first re-do. My intention was to remove all the “tired” garden soil and use it next door at Dreamland to plant our fescue and clover mix into in the two “secret gardens” where the original grass we sowed is battling to get established. But great was my surprise when I started removing the soil. It wasn’t tired at all – it was dead! As dead as a doornail. The top few inches were still loose enough to shovel out, and I will soon use that as a base with some compost mixed in next door. (Lots of long far difficult wheelbarrow trips…) But the bottom two thirds were as hard as rock! The shovel couldn’t even penetrate it. I literally had to use the pickaxe to break it up and remove the clods of dead grey matter in big pieces. (Talk about physical labour…) In the two beds I’ve done up to now, I didn’t find a single evidence of life. No worms, nothing. Even in our hard clay soil, we find the odd earthworm or little organism living. In this dead grey matter, nothing. So either all the nutrients have been depleted – and we seriously need to relook at our crop rotation – which we are doing, or the dry summer killed it all, or (I think) a combination of the two. I mean, those beds have been producing good vegetables for a good number of 6 years.
So the new beds are getting filled from the bottom up with:
- A thick cardboard layer
- A sponge layer of small twigs and leaves that we got from rough mulching some Cyprus we had to trim to get light on the avocados
- A thick layer of straw
- A layer of compost
- A layer of Lucerne chaff
- A layer of compost
- A layer of pea straw mulch
- A layer of compost
- A layer of sugar cane straw mulch.
That about fills a double-sleeper raised box close to the brim. No doubt it will settle down over time as it breaks down. Then I make a little hole at each of the irrigation feeders, into which I plant young seedlings into a small pocket of potting soil. So far I have done one smallish bed for two types of lettuce and some pak choy. This bed is so small I didn’t really bother with companion planting, but I may add a few companions a bit later.
The second bed was a bit shallower, so I left the sugar cane straw layer off. As I started filling this long bed, I got this sudden rush to the brain that I could create an excellent “educational” photo if I juggled the sequence of layering a bit across the two boxes. It cost me a few difficult loads into the middle of the bed – the penalty for having such narrow paths. It’s a pity the photo is a bit hazy – but otherwise I’m quit stoked with the photo. (Not that you would ever teach no-dig beds off a photo.)
In this bed I’ve planted kale, two types of cabbage, two types of broccoli, a few cauliflowers and some pennyroyal and spring onions as companions. It is right next to a bed of mixed perennial herbs too, so hopefully there’s enough diversity to confuse the cabbage moths.
However, resource wise, this is not where we wanted to be. We don’t (yet) have enough tagasaste to harvest, and our real Lucerne is still way too few and small, so we had to buy in Lucerne chaff, pea straw and sugar cane mulch. This time of the year it’s actually very difficult to get hold of good hay or Lucerne. I’ve had to buy the Lucerne chaff from the pet food supplier – fortunately it’s organic horse feed. We’ve also had to buy in a lot of compost as well (10m3 for Homeland alone – but that will cover a few projects). Ideally I’d like to be more self-sufficient in those areas. On the plus side, though, these beds have been producing really well for 5 years before this last dreaded season. Hopefully changing to proper no-dig beds now, with more organised crop rotation, we should get more longevity out of the investment.
You may be wondering why I’m not using our home-made compost? Well, for one, with the dry summer and poor harvest we have had, we don’t have enough compost, and the little bit we have isn’t broken down well enough to be used for vegetables. I may still use partially broken down compost for natives, paths and chicken greens, but with vegetables I don’t take any chances (not again). The other reason I’ll reveal in another post, as I’m experimenting with an interesting resource-cycle project using our own compost.
Well, two beds done, about 10 to go!
I’m no expert on raised beds, so this is just an idea: do you think the bottom soil you had to get out with a pick axe may have been severely compacted rather than dead? I imagine that unlike in the ground, where soil has plenty of other soil to help it along, if the bottom of the bed becomes compacted, there’s no chance for it to sort itself out. My hunch is that every few years, the no-dig beds may need to be revitalised, although the stuff you’re putting in now might be less prone to compaction than soil.
Helen it surely is much more compacted than the normal soil. It must be the shape of the boxes that compacts it, because once I reach the clay underneath it, it is just “normal” clay as everywhere else. Like Nancy (skyeent) suggested, it may be because of the irrigation over the years, because we (nor the kids) never step on it. But I also never aerated it deeply and properly. It’s interesting, there is a lot of material on creating no-dig beds, but very little on what happens 5 years down the line. Although these started off as loam and compost… we’ll see how it goes this time round!
Rain can cause compaction, so I’d agree with you and Nancy that this could be a factor. Still, you’ve got to water, so the solution might be to aerate, as you say.
In normal, ground soil, there would be lots of life throughout the soil but the raised bed is an artificial environment, isn’t it? So, it seems from what you’ve said about lack of info five years down the line that the matter does need looking into. Maybe your post is the start of a new frontier of investigation!
Helen, it is artificial to an extent – sure, it’s built up of layers – but it is not isolated from the ground, the bottoms are “open”, i.e. they rest on the clay soil, so worms and organisms can move in and out of there as they wish and need to. (I guess they all wished to and needed to move out of there – I don’t blame them. Yeah, so starts a long investigation!
I’ve actually just been doing an internet search to find out about compaction difficulties but so far have found nothing. Just lots of glowing reports of how wonderful raised beds are!
What a mess in those beds! But the new beds look amazing. I can’t wait to see how well they produce for you. Maybe try breaking up that compacted soil and add your layers on top to see if that works to revitalize those remaining beds. Can’t hurt to try on a couple of them.
Vicki I’ve been very tempted to only scrape out half of the mess and revitalise on top. However, the bed I did yesterday had a lot of bindweed in, which has quite deep roots, so I just took it all out. But on a cleaner bed I’ll surely try that – break up and aerate the bottom and then build organic layers on top – it’s worth saving 10 wheelbarrow loads!
That old soil looks scary! Do you think that the irrigation washed the clay particles down and therefore caused compaction baked into pottery in the lower part of the beds? Maybe they don’t need to be so deep, or you need a real deep rooted crop/rotation to permeate down again.
Scary is the right word, Nancy! Downright scary. It must have been the combination of irrigation and possibly bad crop rotation – i.e. not enough deep rooted stuff. We never tread on those beds. I’m seriously thinking of getting a strong broadfork so I can aerate the beds better. I think that would also help.
Theoretically it shouldn’t be needed. That’s the whole point of no dig, raised beds isn’t it? Possibly not enough mulch on the surface for the earthworms to work in for you? Maybe the beds don’t need to be so tall – then drainage through them will be less and evaporation off the sides reduced?
Martin, we have a little herb garden on wheels that probably suffer from the same kind of of malady, but on a lesser scale. It’s not as deep and we ask a lot less of it (just a couple of herbs an lately some alpine flowers, just because we can), but I’d like to take some photo’s and PM you with a couple of questions if you don’t mind. Pick your brains, as it were.
Sure Jannes, go ahead!