We have a competition size tennis court (20m x 40m) that we'd like to convert into an annual garden. It is just compacted clay, dug out about 1.5ft below the surrounding land. After a rain, it will be around 1/3 covered with some tough grasses and weeds, but is generally mostly just a red clay cover, teaming with ants. Since the court is already enclosed, since it sits at the bottom of 3 small slopes, and since it is in close proximity to the house, it makes sense (according to my logic) to convert it to a veggie garden.
So far I've looked into hugelkultur, but being in a very hot Australian region with periods of drought each year, it isn't logical to have 5ft tall beds. I then looked into a reverse kind of hugelkultur where pits are dug and filled with organic matter. As we mostly only have access to eucalyptus tree logs which take forever to break down, it would only be possible to use very bulky mulch topped with manure, twigs etc. However, the more I read, the more evidence there is to suggest that disturbing the soil is always a bad idea and that it's better to build new soil on top of the existing layer. I also read that there are dangers when digging into clay soil for planting as because its so compacted, the water gets trapped there and can't escape. At the same time, I've read that this method is good for dryer regions as it holds the water and keeps the plant roots cooler. All in all, I'm pretty confused with all the conflicting info, which I understand is all true based on different regions and circumstances. I just can't find many examples or sources that are specific to my own circumstances.
One thing I know for sure is that nothing can be planted on the tennis court without a help from us, or without waiting a couple of hundred years for it to repair itself. I'm just wondering if anyone can give me some advice that would be specific to our climate and situation so that we can avoid making big mistakes?
At this point, the idea was to dig various sized pits and fill with mulch and organic matter, and have lawn mower wide paths in between which would be planted with living mulches/green manures that could be deposited on the beds after each mow.
Hau,Kate, Converting a clay tennis court to vegetable garden is a great candidate for using several methods, one behind the other to get it ready in only one season.
You mentioned Eucalyptus logs are available, this is a great fuel to use to create Biochar.
Cut the logs into lengths that will fit something like a 55 gal drum. Split these logs into 3-5 pieces for turning into biochar.
A 55 gal steel drum makes an easy to handle charcoal maker, leave the lid solid but poke or drill holes at the bottom of the barrel, this is how air will get in to keep the fire burning. Alternatively you can leave the barrel whole and heat it from the exterior, making the barrel an oven, you only need one opening in such a setup which lets the explosive gasses from the logs escape. either method works quite well for creating biochar. To do the whole court you will need 20-40 cubic meters of biochar if you want to have it done in one season. Once you have the biochar made, wet it lightly and spread it over the court, next is to dig it into the top 1.5 ft. of court clay. If you go with 20 cu.meters of char I would blend it with the same amount of compost before spreading and incorporating it into the clay.
The things that will improve greatly from this are; Water retention, friability of the clay, break up so it doesn't compact tightly again and available nutrients.
The working of the court clay can be done by shovels, tractor with ripper and disc, tiller. This soil disturbance can be done only once or it can be done twice (once per season or once per spreading of biochar, with two spreads done in one season to get enough into the clay). Once you have done this, you can go to sheet mulches of compost and green materials, laid on the surface and they will slowly incorporate down into the clay, making it better and better soil. The first season of cover crops will also work to the building of the clay into really good soil.
If you are going to be doing all this with only hand tools, I would recommend that you mark out beds for this year, work them so you have a garden going then work on the spaces between these or plant some cover crops in the between spaces with the idea of digging them in along with biochar and compost as you can.
With effort you can do large things, a little at a time. This keeps folks from throwing in the towel from exhaustion.
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