As the soil around Canberra tends to be crap, I decided to start out with a simple no-dig garden bed. This means that you basically build your own top-soil layer on top of your lawn, and is perfect if you want to be relatively lazy about it.
You can even do this on concrete if you make it thick enough (at least 30cm once it’s decomposed) but on grass you get the benefit of encouraging earthworms to come and visit – their slime is the magic ingredient to help build soil structure. (Personally, I thought this was a bit of a myth before I started as I couldn’t see how earthworms could even live in the soil here to be able to get to the no-dig bed, but I found some the other day so… myth busted!)
I read up on no-dig techniques beforehand from different sources and they pretty much said the same thing (lucerne hay is vital, and you need some blood & bone, chicken manure etc for a fertilier.) This is actually rubbish. All you need is some organic material that can break down over time. Yes, lucerne hay (alfalfa) is good, but you can use other types of hay or straw or whatever.
Here’s what I did for my ‘vegan’ no-dig:
- Made a border with 4 wooden posts and folded hessian cloth wrapped around the outside (stapled in place)
- laid down some newspaper sheets and wet them (just so that underneath grass etc dies off)
- Put down a thick layer of sugar cane mulch.
- Thin layer of compost (my own mixed with a few bags of mushroom compost)
- Thin layer of hay (I did use lucerne)
Wet the lot. Oh, here’s a tip – if you’re going to collect bales of hay, make sure you use a trailer or get them to deliver it. I stuffed a couple in the car and it took several hours to clean up 😦
Now wait. I waited for about a year because I’m lazy, but I’m sure you only need to wait a month or two. Wet it occasionally and the organic matter will start to break down and the bed will shrink down as it decomposes. If you’re really keen you can add extra layers until it’s nice and thick. You need it to break down as there needs to be enough substance for roots to grow into, otherwise they wouldn’t be able to absorb nutrients and water.
I like the hay on top as it protects the underlying soil from getting baked (our summers get scaldingly hot) and keeps in a fair amount of moisture, although it can interfere a bit if you’re growing things from seed.