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GARDENING Autumn leaves a gardner’s godsend

Outdoor Living

Hans Weiland takes a look at soil, compost, leafmould and humus

As many veg gardeners come to the end of the growing season and clear their beds after harvesting, there is a lot of compostable material around, from outer cabbage leaves, dried stalks of your onions, empty pods from your beans and more.
This can all be composted and although we are going into the winter season, when temperatures are lower, it still makes sense to build your compost heap.
A good mix of thin layers (three inches) of green (rich in nitrogen) and brown (rich in carbon) ingredients makes perfect compost. Always have enough brown material at hand to mix with your green garden or kitchen waste; straw is ideal.
Remember to cover your compost heap if you don’t use a container, to avoid nutrients being washed out by the rain.
If you have cleared your vegetable beds and want to spread compost or half-rotted compost on top of the soil, cover it with a mulch membrane or black plastic for the same reason.

Making leafmould
Now is also the time to make leafmould. As you’ll have already noticed on your walks in the countryside, broad leave trees are shedding their leaves. Some people see this as a nuisance, but many gardeners see it as a godsend and collect as many leaves as they can get their hands on.
Simply rake up fallen leaves. Take care not to use ones from sides of busy roads though, as these may have heavy metal contamination from car exhausts. Pile the leaves into a frame, made from four posts with mesh wire around the sides. This is simply to prevent the leaves from blowing away. Don’t cover the heap and allow the leaves to soak up the rain. In twelve-months time the leaves will have rotted to a crumbly mix, and in two or three years, this will be softer, finer and closer to the spongy state of humus.
You can dig your one-year-old leafmould into the soil or spread it on the surface as a mulch.
To make your leafmould even better, you can add comfrey leaves to the mix. Comfrey on its own is a very good source of liquid fertilizer and a valuable manure in its own right. The leaves are rich in potash and also contain nitrogen and phosphate. If you have maintained your comfrey plants throughout the summer, you should still have plenty of green leaves on them, cut now and use them for composting before they die away.

Building Humus
Garden compost and leaf compost are the humus builders that you can add to the soil. Compost is not humus yet; it still has visible pieces of plants that will root for a good while yet. Compost can be seen as the first stage or a stage in the production of humus.
Renowned gardener Joy Larkcom says in her book ‘Grow your own vegetables’: “Humus is organic matter in a very advanced state of decay, and it is from humus that plant nutrients are released.”
I think we can simply say that humus is plant and animal substances that have decomposed to a point of stability. In other words they have rotted down to a substance that can’t rot any more. It improves soil structure and increases water retention. Its nutritive qualities include trace elements and several important organic acids but do not include nitrogen or phosphorus.
Compost, on the other hand, is organic matter in a purposeful state of partial decomposition. The purposeful part is important. Dead stuff on the ground is NOT compost, just decaying organic matter. It is the controlled, or semi-controlled conditions that make it compost, which in essence means we gardeners have to mix the ingredients, as described above, well!

International Year of Soils
This year, 2015, is still the International Year of Soils as declared by the UN’s Food and Agriculture Organisation. A new film has been released by Deborah Koons Garcia called ‘Symphony of the Soil’.  What a wonderful title. I haven’t seen the movie, but the trailer looks absolutely amazing. I’d highly recommend it.

Hans Wieland is training manager at The Organic Centre, Rossinver, Co Leitrim, which offers courses, training and information on organic growing and cooking, and runs an Eco Shop and an online gardening store. For more information, visit www.theorganiccentre.ie.
Gardening questions or comments? Contact Hans at living@mayonews.ie.