Some thoughts on composting
Within Dokmai Garden’s tropical gardening school we emphasize composting, and we have earlier arranged for a composting talk, but some people have remarked there is no blog about it. So, here it is:
What is compost?
Compost is an organic mulch of mainly dead plant debris, degraded by fungi, bacteria, worms and insects.
What is compost used for?
Compost improves a clayey or sandy soil by adding organic matter, thereby improving the water holding capacity, the aeration and adds a useful microbial flora. It is not a main source of nutrients, although many micro elements can be found there, or be supplemented to a commercial compost.
Why would you compost in your own garden?
I think it is convenient and fun. Having a supply of good soil will allow sudden bursts of initiative, no need to go downtown to buy soil first. Another option is of course to stack plenty of commercial bags, such as from Natural Agriculture Co Ltd (composted elephant dung and teak waste, sold at Dokmai Garden). Also, most gardeners get a lot of unwanted plant debris and do not know what to do with it. Burning is a bad option – making something useful is better. The fun part is that it is home made, you get an understanding for what soil is, and many interesting critters dwell in the compost.
How do you make a compost?
The compost needs
1) Dead plants
4) To be turned regularly (once every 1-2 weeks)
A pile of debris can become a compost too, but tends to flatten out and thereby occupy an unnecessarily large area. In colder climate, you need to have a certain thickness to speed up the composting. In a wet climate you can use a simple cage, but in a dry climate such as Chiang Mai’s I suggest making three walls and a door. Do not cement the floor, simply put some branches in the bottom. If you have three compartments of compost one can be the one you actively fill, one can be resting but turned and watered to mature, and one is mature from which you collect soil for your garden pots or vegetables. A dry compost is dormant, nothing will happen.
Can I compost kitchen waste?
Yes, at Dokmai garden we composted kitchen waste until we got our wild boars. It is important though that you dig down the kitchen waste deep into the compost or there will be a bad smell attracting flies. You should also make sure there is not too much nitrogen (protein, e.g. fish and meat). Bamboo and banana consume a lot of nutrients and so kitchen waste of animal origin can be fed to these plants. An older filter with coffee is easy to compost.
Can I compost any part of a plant?
Yes – but while some parts degrade quickly, pieces of hardwood or avocado seeds need to be fragmented to obtain a decent speed of degradation. We mainly feed our compost with leaves and smaller twigs. If you have the time you can use an axe for the branches and a hammer for the hard seeds. Some people buy a mulcher and then they can compost anything at a high speed. Since I hate noise and do not like big costy machines for simple tasks we simply stack big branches or spread them out. The termites transform them into powder in a year.
My compost is full of longan leaves, I water and turn, but very little happens – what is wrong?
Brown leathery leaves with high tannins and no nitrogen or phosphorus (which you find in green leaves) may take quite some time to compost. Add one third of soil or old compost and mix with the leaves and add some nitrogen which is needed by the micro organisms (manure or urine or green grass cuttings or green bean plants).
Can I urinate into the compost?
Yes – but not regularly or there will be a terrible smell. Unless you are ill urine is sterile when it leaves the body, not dirty, but should always be diluted 1:10, at least. Peeing straight against a plant may kill it (watch your dog). You can fill a watering can and urinate straight into it and then bless a selected plant. In fact 24 hours of urine production is enough for the entire life time of a broccoli plant. In old China travelers were paid to urinate in certain places, so that the farmer could use the urine.
Compost spreads many weeds, I prefer to buy my soil.
If the compost has been treated correctly, i.e. all parts of the compost have been in the centre at least once, then there should not be any problems. In the centre, heat develops as a result of the degradation. The high temperature kills most seeds. To be on the safe side, omit weeds such as sensitive mimosa (Mimosa sensitiva) and apparently sick leaves.
Do I need to buy special worms?
If you wish – but it works fine with native worms too. Your compost will be a good place for native worms when fishing.
Sometimes I buy commercial soil with a strange smell.
Sometimes it simply smells microflora. Geosmines, the soil smell, comes from actinomycetes, special soil bacteria. Sometimes the compost smells mouldy, but moulds are a part of the degradation process. It is the smell of life! Sometimes it smells sulphur, that is due to water logging in a plastic bag making H2S producing bacteria thrive. If you simply spread out the soil on the ground the smell and excess water will go away, and afterwards you can use the compost.
Are there any special conditions to keep in mind here in the tropics?
Yes, degradation is swift and almost total. If you study the soils in the forests, they have very thin organic soil layers. Partly due to the past devastating clearcuts and the annual illegal fires, but also because the plant debris when composted turns into living beings and carbon dioxide very rapidly. Therefore, a one cubic metre of garden waste may only result in a small fraction of soil, so you may want to use the soil already when semi-degraded. Sieve with a plastic net if you want a perfect soil without clumps.
Also, composting is new to many Thai farmers. They consider garden waste as any garbage, and would happily burn it or dump it on your neighbour’s land. If you try to teach them how to compost, they will think you are mad, and that you disrespect them by asking them to touch something dirty (like emptying a toilet). Better make your compost yourself, make sure they watch you when you turn the soil and then you use the compost when planting. Gradually they will think composting is a natural part of the gardening job. Then they will start trying to compost plastic bags and cigarette packages, and then you need to explain that such garbage belongs to the bin, not to the compost.
I have never seen a fork spade in Thailand, but if you find one abroad bring it to your garden! This one was made in Sweden and has served Dokmai Garden for many years.