Trench composting

Trench composting  systems are effective for provide compost to   rows of beans, marrow beds etc.  etc or as a rotation system to compost the whole garden over a period of years. Alternatively,  individual holes can be dug where space allows in the garden. At the simplest level a spade or post hole digger can be used to make an  8-12" deep  hole the width of the hole can be varied to suit the volume of waste which should be at least 4" deep in the hole. 

In-ground trench or pit composting provides a simple  way for composting fruit and vegetable waste including uncooked kitchen scraps. Techniques that involve burying the organic material have the advantage that no special equipment is required and once the material is buried there is no visible evidence that composting is being undertaken.

 As decomposition in underground composting happens more   slowly than in the more usual bin systems it. is perhaps more important than in normal systems to expose the maximum surface to microbial activity. Cutting the waste to about two inches in  length is recommended. The green and browns can be mixed  in the pit using a fork of spade, but I find it is easier to mix them before adding to the pit.  

One of the concerns expressed by people new to trench or pit composting is that it will attract rats and other animals looking for a free meal particularly if it is left when only some of the waste has been added and it is not yet covered by the  four-inch  layer of organic material. The waste in the pit can be covered with a thinner layer of soil and the whole pit covered by a sheet of plywood. Once  the waste material  reaches the depth of four inches  the pit should be  filled with soil. 

If the  material  is kept moist (it may need watering) it should  decompose in about a year   after which the area can be planted. 

  Pit composting (see below) is suitable for an area where there is limited space either because the garden is small or is permanently planted areas such as perenial flower beds.

Trench composting is usually used in the vegetable garden so that composting can be started in the late summer or autumn with the trench being filled and ready for spring planting of runner beans, french beans or peas. 

 Trench composting can be started earlier, if space is available on the plot, so that  chopped brassicas stalks can be  included as this offers an easy method of composting the  stems which may be slow to compost in a conventional compost bin. Trenches can also be dug between rows of plants or seeds

A similar method where circular pits are dug, rather than a trench, can be used for courgettes and pumpkins.

The   trench is often dug for convenience about a spade width and depth the length of the required bean row, which might be across the width of an allotment plot. It is worth checking the recommended planting distance for the beans as; if a double row is required the trench will need to be wider.

Place the soil along the side on the trench so that it may be used to cover the composting material as it is placed in the trench. Start added the waste at one end of the trench covering it with the soil as it is added. Some people dig a deeper trench so that a second layer of waste can be added but this will depend on the quantities of waste available and the number of rows of beans to be grown. When the waste has been covered the soil is likely to have made a small mound along the length of the trench but this will settle by the time of planting. I would suggest marking the trench with small sticks so the it can found in the spring when you need to plant in it.

 Some gardeners use trench composting as part of a composting rotational system where the trench is moved across the garden each year.More information can be found at 


Year 1

Compost trench

Access Path



Year 2





Year 3






Post hole, Pit Composting or Chop and Drop composting

Post-hole and  Pit composting are variations  of trench composting and  using a permanent pit or a temporary pit or pits for a single season.  

The “chop and drop” method simply  involves chopping the waste into small pieces with a spade, digging a post-hole  in the garden,  dropping the waste into the hole, giving it a final chop in situ and  covering with  soil. It is sensible to mark the spot when rotating  the sites round the garden. Mark the spot with a small stake and rotate around the garden.  If using fresh green garden waste, it can be covered with  a layer of straw before the soil is replaced to help retain more of the nitrogen.

Usually when making a larger temporary pit a hole is dug to a depth of about twelve inches or for ease of working this may be one spit (the length of the spade blade).The size of the hole may be about three feet wide or be varied depending on the quantity of waste available for composting.  In a temporary pit a 3-4-inch mixed layer of organic material is added to the bottom of the pit. If vegetable gardening in rows it may be helpful to make the pit the same width as the row normally used. 

If a permanent pit is being dug the area chosen should not be close to the house as it might smell. It is best  a sunny part of the garden to keep the  compost pit as warm as possible.

 If a permanent pit is being planned it is usually dug g 2-3 feet deep with the sides of the hole being lined with bricks to avoid  them collapsing  into the pit with use. 

 Whichever method is being used it may be necessary to stockpile  the material so that there is enough to provide a layer in the pit. It is important that the material is cut into small pieces to expose as large a surface area as possible to the action of the composting organisms in the pit  so for ease of cutting I would advise that this is done while the material is still fresh before it is stockpiled even if it is only being kept for a few days. The  Greens and Browns should be kept separate until the time to add them to the pit. However, they should be mixed well either as they are added to the pit or once added to the pit. Some use a spade to mix the materials, but I find a fork easier.

If there is insufficient material to fill the pit it can be left for a week or so provided the waste is covered with a layer of Browns e.g. autumn leaves or shredded paper . The hole should be covered with a board or strong weldmesh  to prevent animals gaining access

 Replace the earth in the pit  and water and continuing the watering to keep the soil (and composting material) moist.

The material may take up to a year to be fully decomposed but if the pit is made in the late summer early autumn it can be used for planting beans in a pyramid, courgettes or pumpkins in the spring.

The mixed Greens and Browns  in the compost pit can be layered with manure  and soil. A layer of the mixed organic materials is added first followed by a layer of chicken, horse, cow or manure followed by a layer of soil.  Another layer of mixed organic material is then added and followed  by manure and soil the pile reaches 1 foot above the ground level.

Some composters using a permanent pit also  add a layer of Blood meal to the organic material to speed the composting process before covering with soil. The compost ingredients should be turned  in the pit weekly to provide proper aeration. Water after turning to  keep the pile moist.




Composting in small or hard landscaped garden

The above information may be read to imply that composting requires a large or medium size garden but in fact composting is practical in a garden of any size even if completely hard landscaped and indeed may be used with household kitchen waste  in an apartment, flat  or patio.

A suitable composting bin, wormery or bokashi bin can be placed on be used as a feature in the garden, painted by the children or grandchildren or  screened by trellis growing plants.

A conventional style plastic bin that would normally be placed on soil can be purchased with a plastic base or stood directly on the concrete or decking with some soil or mature compost being added to the bin as a starter. If too much leachate is produced it might stain the concrete or timber but this can be avoid by standing the bin in a cardboard or wood chip to absorb any liquid and monitoring the contents so that they do not get to wet.

If the bin is cannot to be hidden by trellis wooden beehive bins are  aesthetically pleasing and add an interesting feature to the garden.

Tumble bins are normally mounted off the ground on legs. The original tumbler  where quite large bins and consisted of a single chamber and were most suited  for batch composting but   there are now quite small dual chamber tumblers which allow continuous composting.

Wormeries provide  an interesting alternative to a compost bin and  are normally equipped with legs of stand on a base up off the ground. A commercially available plastic wormery is suitable for kitchen waste supplemented with shred paper and cardboard. There are versions available for use on balconies and even indoors.