Organic Matter – Building the Soil
This is a massive and essential topic. I think Matthew Evans probably sat down to try and write a short post like this and then ended up with the book ‘Soil’, which is a great read for the details. I’m going to try and concentrate on what I’ve done and why. Soil is tied up in everything as a gardener, so I’ll be referring to different aspects of it regularly.
Buying and building soil is a minefield. Most of the ‘Veggie Mix’ that I’ve purchased in bulk arrives on my driveway still steaming hot. The pH around 9 – nothing can live at pH 9. Nothing. How are you supposed to grow food in it? The only solution is to wait until it calms down and finishes the composting cycle, which could be as long as a piece of string. The pH yo yo’s up and down during composting as different organisms and bacteria do their job. I usually spread it on the garden bed and mix it in with other organic matter, but I’ve heard some people leave it in a pile and keep testing it until it has settled to around pH 7. Either way, after a while it will be OK to plant in.
Building my own soil is also a waiting game but from my experience seems to be the quality option. By far the best results I have had are no-dig layered, lasagne style garden beds. For big bulky, deep amounts I try to get some relatively cheap sandy ‘fill’ (with a bit of clay in it) and then mix it with mushroom compost, decayed wood chip and my own compost. I once filled a raised bed solely with bush turkey nesting material (100% organic matter) – two cubic metres of it. Over the next two years it decomposed, and the surface subsided about 300mm. I had to dig up the trees, fill up the garden bed again and then replant the trees. Not cool. The sandy fill provides the structure to limit the subsidence.
Adding quality organic matter to this sandy fill provides the missing ingredients to amazing productive soil. Introduce a variety of bacteria, worms, fungi, and other microscopic life via compost, worm wee, compost tea and weed tea. There is nothing commercially available that is anywhere near as good as home-made compost. The real Black Gold. I make compost from a variety of different plants, poo and urine which increases the variety of life. The best explanation I have heard for compost is that it is yoghurt for the soil. Just like we humans need a dose of the healthy yoghurt bacteria, so the soil needs compost bacteria little and often.
The wait is for the soil profile to develop and life to proliferate. Disturbing this soil profile by digging gives a short-term boost in nitrogen, but it destroys the soil profile and therefore the life in the soil, and the nitrogen needs replacing with fertiliser. A lot of the nitrogen is lost to the air by turning the soil over.
Different organisms thrive at different depths in the soil and they all do a job helping you grow healthy plants. Minerals the plants need to thrive are often locked up in various ways, these organisms form a complex web of breaking everything down, helping different nutrients become available to plants.
We are not so much growing plants as feeding soil – the plants will look after themselves with healthy soil.
Just keep adding organic matter to the surface and let the soil life work its magic. Use what is easiest to get hold of without skimping on quality. At this point in time I have oodles of decomposed wood chip, so that is what I used for the bulk. About a 10-15cm thick layer – this will break right down in time to a fraction of the volume. Then I have covered this layer in home-made compost. The last compost I made wasn’t amazing – I tend to get lazy with chopping things up finely. But it is still full of life as the worms were happy to pose for a photo.
Finally, I watered it in with home-made worm wee. One part raw wee from the worm farm to nine parts water. This equates to about one litre of raw wee in the bottom of a watering can and then fill it up with water. Rough amounts – no-one is keeping tabs on accuracy, I hope.
When I was researching making sourdough bread a chef mentioned that the reason we fold the bread is to introduce the bacteria to new food and promote even gluten development. The bacteria aren’t marching through the dough looking for food, they feed on whatever is immediately local. In the garden I’m trying to avoid ‘folding’ the soil by digging, as the soil profile needs to be maintained intact. I like to think that by watering in the compost with worm wee (or plain old water) I am swilling a few of these bacteria deeper into the moist soil where they will breed and repay me later.
Organic matter provides the sponge that soaks up water in surprisingly large quantities and prevents soil from drying out too quickly. I’m sure everyone has picked up a piece of rotten timber and it is moist and spongey. Imagine a piece of very rotten wood in tiny pieces sprinkled liberally through the soil. Keeping the soil moist keeps bacteria alive, the worms happy and nutrient dense food should be the result!
One other point that people don’t talk about much – tap water contains chemicals to kill the bacteria in the water – it is indiscriminate. Gardening is about trying to breed soil bacteria, so I choose rainwater wherever possible.
Woo hoo, I haven’t written a book, at least not yet.
