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Composting

What is composting?
Composting is the decomposition of waste plant material to create a bulky organic matter (compost) that can be used to improve the soil in your garden.

Some clarification over the term ‘compost'
The gardening industry have confused things slightly as the word ‘compost' generally refers to the multi-purpose compost that you can buy from the Garden Centre. This can be used in planting up containers but has little or no bulky organic content and does not improve the soil in your garden, so has little benefit if added.
If you want to improve your soil, for example if you have sandy or clay soil you should add bulky organic matter in the forms of: Garden compost, Leafmould (both of which can be home made), Well rotted farmyard manure, Mushroom compost and Composted bark.
nB Mushroom compost is alkaline and so do not use this around acid loving plants like Camellias.

Why should we compost?
You can use home-made compost either as a layer on the soil surface (mulch) or dug into the soil. I add a 5cm layer to my soil every Spring topped up with farmyard manure from the garden centre if I don't have enough. Used as a mulch like this it can help to retain water in dry spells, keeps the soil warmer and keeps down weeds. Eventually, worms take it down into the soil and it improves the soil structure. I also add some to the backfill soil when putting in a new plant.

Once in the soil, it improves the drainage on clay soils and improves water retention in sandy soils. Soil becomes easier to work, plants root more easily, and some nutrients are released for the plants to use. In addition, by using home made compost you are reducing the amount of waste going to landfill, and reducing transportation costs of moving waste out of the garden, or importing new compost in, and don't forget it's good for the pocket too as it's a free resource.

How does it work?
The soil is teeming with micro-organisms which break down organic material into smaller particles which help improve the soil and eventually releasing food for plants.

What container should you use?
There are a variety of compost ‘bins' available. Plastic compost bins are often available from your local council at a reduced cost but I personally prefer a timber construction. You can buy these or if you are good at DIY, or know someone who is, you can make one.
It should be 80-100cm2 and about 1-1.5m high, and if you have the space have 2 or even better, 3 of these.
The sides can be solid or slatted. Slatted is often recommended as it increases air flow into the heap but I have a solid one and turn it every month to aerate it which seems to work well.

Where do you site it?
Preferably site the bin in a location which gets the sun for half of the day, although the compost will still decompose in the shade, just a little slower.
Ideally it should stand on soil to encourage micro-organisms to enter the heap.

What do you put in it?
You can put in:
Soft waste: Plant stems, grass clippings, annual weeds, vegetable peelings, egg shells, tea bags, coffee grinds.

Woody waste: Chipped woody waste, scrunched up newspaper or waste paper, toilet roll inners, small pieces of torn up cardboard, shredded paper (not heavily printed or glossy though)

Don't put in: Cooked food, meat, cat litter, perennial weeds, large pieces of wood, and plant material including grass which has had chemicals applied to it.

In a full heap there should be about 60% woody waste and 40% soft waste.

The material needs to be added in layers, so, for example, if you have just added a layer of soft waste e.g. grass cuttings, you then need to add a layer of woody waste e.g. scrunched up newspaper. This will give an optimum ratio of material for the micro-organisms to work and keep it aerated (They need oxygen to survive).
If you put too much soft material in e.g. lots of grass clippings, it becomes too densely compacted, oxygen cannot get in and you will start to get anaerobic decomposition (without oxygen) which is slower, does not kill off all weeds and seeds and can often make the heap smell.

Managing the heap
If you only have the space for one heap, you will need to fill up the container and put an old piece of carpet over the top. This helps to retain the heat and stops it getting too wet, but you also need to make sure it does not dry out in hot weather, so water if necessary. Leave it for 6 months by which time it will be ready to use.

If you have space for a 2 bin system, you can either do the above in both of them, or, as I do, keep adding to one only and leave the other vacant. Every month or two, if you are feeling energetic, turn the heap into the other container, but keep adding only to the filled one leaving the other one to turn into. After a few months of doing this you will find that the material in the middle and sometimes at the bottom is ready and can be taken out and stored or used.
(I use old compost or bark bags to keep mine in until I want to use it).

If you have a 3 bin system, like this one at Stockwood Discovery Park in Luton you take the following approach:

 
Compost Bins
Fill Bay 1 with material.
   Bay 1 - Full  Bay 2 - Empty  Bay 3 - Empty  
After a month or two turn this material into Bay 2 so you have:
   Bay 1 - Empty
 Bay 2 - Full  Bay 3 - Empty  
Then fill Bay 1 with new material until after at least a month and when it is full
   Bay 1 - Full  Bay 2 - Full/Decomposing  Bay 3 - Empty  
Turn the material from Bay 2 into Bay 3 and Bay 1 into Bay 2
   Bay 1 - Full  Bay 2 - Full/Decomposing  Bay 3 - Full/Decomposing  
Then start to fill Bay 1 again with new material.
When the material in Bay 3 is ready, remove it and either use it or store it, and turn the material from Bay 2 into Bay3 and Bay 1 into Bay 2, and continue like this. Only ever add fresh material into Bay 1 and allow the other bins to decompose fully.
 

 

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