Pits /underground/ trench Method of

Composting By

Allah Dad Khan

Pit composting • For pit composting, holes or trenches are dug to bury

your waste. After that, you sit back and forget about it, while the organic materials gradually break down over a period of six months to a year. This method is effective for those who want their decomposing organic matter to be completely out of sight. The trench is also a good place to stick those weedy plants you have pulled up. If buried deep enough, the weed seeds will not see the light of day, so they won’t resprout

Why is compost important?

• Compost is important because it:1. Contains the main plant nutrients – nitrogen (N),

phosphorus (P) and potassium (K),2. often written as NPK;3. Improves the organic matter in the soil by providing

humus;4. Helps the soil hold both water and air for plants; and5. Makes trace elements or micronutrients available to

plants.

What is needed to make compost?

• Plant materials, both dry and green1.Weeds, grasses and any other plant materials cut from inside and around fields,

in clearing paths, in weeding, etc.2. Wastes from cleaning grain, cooking and cleaning the house and

compound,making food and different drinks, particularly coffee, tea, home-made beer, etc.

3. Crop residues: stems, leaves, straw and chaff1 of all field crops – both big and small – cereals, pulses, oil crops, horticultural

crops and spices, from threshing grounds and from fields after harvesting.4. Garden wastes – old leaves, dead flowers, hedge trimmings, grass cuttings, etc.5. Dry grass, hay and straw left over from feeding and bedding animals. Animal

bedding is very useful because it has been mixed with the urine and droppings of the animals.

Pit Compost

• If you live in a place where digging holes in the ground is no big deal, you can make a pit compost. The following info helps you add anaerobic composting to your repertoire. Good choices for your pit compost include areas where you want to add a future garden bed or between rows of existing garden beds. Avoid marshy areas or low spots with wet soil or poor drainage.

Pit Compost contd

• Stay away from existing root systems when digging composting holes. Tree and shrub roots easily expand to twice the diameter of their aboveground canopy! Slicing through roots with a shovel creates easy wounds for pests and diseases to enter, ultimately weakening and possibly killing your plant. If you're unsure how far roots may have spread, stick to digging compost trenches in garden beds.

Pit Compost contd

• Depending upon what you want to achieve, you can employ several different methods of pit or trench composting, such as digging random holes, filling trench rows in garden beds, or rotating trenches over a three-year period to improve an expanded planting area. Use the basic anaerobic trench compost recipe that follows for whichever method you choose.

Pit Compost contd

• How deep and wide to dig depends on how much organic matter you have to compost, what kind of material it is (landscape waste versus kitchen waste), how easy it is to dig, and whether digging pests might be an issue.

Steps For Compost

Follow these steps to create a pit compost.1. Dig the hole or trench, reserving the soil that you

remove.2. Start with browns on the bottom, alternate layers of

brown and green materials, moistening as you build.3. Spread a 1-inch (2.5-centimeter) layer of your

reserved soil between layers of browns and greens.4. Cover with 4 to 8 inches (10 to 20 centimeters) of

soil. If you plan to retrieve the compost later, mark the area with a stone or other reminder.

Steps contd

1. Dig the hole for your compost pit. Your compost hole should be about 1 foot (30 cm) deep. The area of the hole will be determined by the amount of organic matter you want to add. Keep in mind that the compost will be finely chopped and piled to a height of 4 inches (10 cm) in the bottom of the hole when estimating the hole's size.

Steps contd

Steps contd

2. Chop your composting materials finely. Underground composting proceeds more slowly than above ground setups, and maximizing the surface area of your scraps is key to speeding the process. Kitchen scraps can be ripped apart by hand, chopped with a knife, or even pulverized in a food processor. Yard scraps can be broken down using a lawn mower. Aim for pieces no bigger than 2 or 3 inches (5 - 8 cm) in any dimension.

Steps contd

3. Add the organic materials to the compost pit. Pile your food scraps and yard waste into the hole you dug to a depth of about 4 inches (10 cm). Make sure your carbon-rich materials (such as paper and dried leaves) are mixed thoroughly with your nitrogen-rich materials (like vegetable scraps and fresh grass clippings), as you will not be turning the underground pile.

Steps contd

4. Place a board over the hole if you plan to add more scraps. If you want to be able to continually add scraps to the compost pit, cover the compost with a thin layer of soil or carbon-rich material. Then place a wooden board over the hole to prevent anyone from tripping into it. Be careful not to add materials to a depth of more than 4 inches (10 cm), as this will make it difficult to adequately cover the compost with soil later.

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5.Cover your compost with soil. Once you have finished adding your organic scraps to the compost pit, you can backfill it with the soil you removed. Add the soil on top of the compost, filling the pit until it is again level with the surrounding soil. Recover with sod or seed with grass if desired.

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6. Keep the compost pit wet while it is decomposing. Underground compost decomposes slowly, because it doesn't have access to as much fresh oxygen as above ground piles. To speed the process, ensure the area stays fairly wet. During dry weather, soak the ground above the compost pit with a garden hose. Inadequate moisture will prohibit microbes from breaking down your scraps. If the area is kept sufficiently moist, underground compost should be fully decomposed in about a year.

Steps contd

7. Sow plants above the compost after it has decomposed. A major benefit of underground composting is that you don't have to perform any extra steps to harvest the compost and amend your soil. The work is done for you, as the decomposed scraps will work themselves into the soil naturally. The best way to take advantage of this benefit is to plant your plants directly over the area where you composted your scraps. In fact, each season you can cycle the locations where you grow plants and compost; this will ensure your plants' soil is always freshly amended with organic matter

Points to remember when making compost in a pit

1. This is good anytime of the year where moisture is limiting, and is the best wayto make compost after the rains have finished and during the dry season. 2. Prepare and dig the pit, or better still, a series of three pits, when the land is

moist and easier to dig, and/or when there is a gap between other farming activities. 3. If possible, make the compost immediately at the end of the rainy season whilethere are plenty of green and moist plant materials. 4. In the dry season, make the pit near a place where water can be added, e.g.

next to the home compound where waste water and urine can be thrown on thecompost materials, or near a water point, e.g. a pond, or near a stream whereanimals come to drink. 5. Mark the place of the pit with a ring of stones or a small fence so people andanimals do not fall into it accidentally

Selecting and preparing the site

1. It should be in a place that is easy to take the materials,including water and urine, to the pit as well as for watching and follow-up.

2. The site should be protected from strong sunlight and wind. It can thus be, for example, in the shade of a tree, or on the west or north side of a building or wall.

3. The pit should be marked or have a ring of stones or a fence of branches around it so that people and animals do not fall into it.

4. The site should be protected and away from where floods can come

Digging the pit

1. The minimum size of a pit should be:I. }1 metre deep (pits should NOT be deeper than 1 metre)II. }1–2 metres wideIII. }1–2 metres long2. If a farmer and his/her family, or urban household, can collect more compostmaking materials, the pit can be made longer, but NOT either wideror deeper.3. If a pit is deeper than 1 metre, the material at the bottom does not get decomposedbecause many of the micro-organisms cannot live so deep down as the oxygenthey need will not reach them.4. Before any materials are put into the pit, the sides and bottom should be checkedto make sure no water is leaking into the pit.5. The bottom and sides should be plastered with a mixture of fresh animal dungand water, or top soil and water, to seal the surface so that the moisture in thecompost materials is kept in the pit.

Filling the pitThe foundation layer1. Dry plant materials, e.g. strong straw, stalks of maize and sorghum or tall

grasses,as well as rose and hedge clippings from gardens, are used for the foundation.

Theseneed to be crushed or chopped or broken into short lengths (about 10–15 cm). Ifpossible, let the domestic animals walk over them and sleep on them for one ortwo nights so the materials get broken up and mixed with urine and dung.2. Spread the materials evenly over the bottom of the pit to make a layer 15–25 cmthick. Then sprinkle/scatter water evenly so that the materials are moist, butnot wet.3. This is a very important layer in making compost in a pit as it makes sure thatair can circulate to the bottom.4. Cover the foundation layer with large leaves, e.g. those of pumpkin, banana,fig leaves etc., and/or plastic to keep the material moist

Putting the other layers into the pit

1. Each week, collect materials and put them in a container such as an old jerrycan or pile them next to the compost pit. Mix the fresh moist materials withdry ones. These materials can come from spoiled animal feed, old animalbedding, from cleaning the house and compound, preparing vegetables forfood, clearing paths, weeding, stems and leaves after harvesting vegetables,damaged fruits and vegetables, etc.2. If the farmer has a biogas digester, the bioslurry can be collected also to be mixed with the other materials. The bioslurry is an excellent compost making aid.3. At the end of a week, remove the large leaves or plastic covering the top of The foundation layer so they can be used again, or leave the leaves to become part of the compost if they are too damaged to be used again

Putting the other layers into the pit contd

4. Make a mixture of compost making aids like good soil, manure and/or someashes as a fine powder. Mix these with the dry plant material, or with the mixtureof dry and moist plant material.5. Add the prepared composting materials in layers. Each layer is 15–25 cm thickat the edge and a bit thicker in the middle so that the heap becomes domeshaped6. Cover each of the layers with a thin layer of soil and/or big leaves like those from banana or pumpkin or fig trees so that the composting materials do not dry out.7. Repeat this process each week, or whenever there are enough materials collected to make one or two new layers, until the pit is full. Make the centre of the layers in the pit higher than the sides so that the top has a dome shape.8. Put a ventilation and/or testing stick into the middle of the pit.

Making the covering layer

The pit full of composting materials needs to be protected from drying out, and also from animals disturbing it.1. The covering layer should be made of mud plaster, with

or without cow dung, with only the ventilation stick coming out of the top. It is then covered with wide leaves of pumpkin, banana, fig trees, etc. or plastic can also be used to protect the top of the pit. The leaves or plastic:

i. Prevent rainwater from getting inside the pit; andii. Help keep heat inside the pit.

Making the covering layer contd 2. The compost pit can be left untouched until there is mature compost inside it,or it can be turned over and checked for the progress in decomposition. Thetop of the pit will sink down as the compost materials get decomposed. However,if the compost is turned over, it will lose moisture. So, it is best only to turncompost over if there is enough water and/or urine to make it moist again whileit is being turned over.3. The process for turning over the compost from the pit is the same as thatdescribed for the Indore pit method. In a warm climate, mature compost can be made in three to four months. In colder climates, decomposition can take six months or a year.4. The mature compost can be left covered and stored in the pit until it is neededfor adding to the soil.

Trench Composting

This is the simplest way for composting kitchen scraps. Dig a one-foot-deep hole. Chop and mix the food wastes into the soil then cover with at least 8 inches of additional soil. Depending on soil temperature, the supply of microorganisms in the soil and the content of the materials, decomposition will occur in one month to one year.

Trench Composting contd

Food waste burial can be done randomly in unused areas of the garden or in an organized system. One system is to bury scraps in holes dug around the drip line of tress or shrubs. An English system, know as pit or trench composting, maintains a three season rotation or soil incorporation and growing. Sometimes this is also called Vertical composting. Divide garden space into 3’ wide rows.

Year 1 – Dig a 1’ foot wide trench on the left hand 1/3 of the 3’ area (A). Add compostable materials in this trench and cover with soil when half an inch full. Leave the center 1’ section open for a path (B), and plant your crop in the remaining

1’ strip along the right side (C)

Year 2 – Section A is a path for year 2 allowing time for the Materials to break down. Plant your crop in section B. Section C, where you planted last year, becomes the compost trench.

Year 3 – Section A is now ready for planting. Section B is your trench for composting. Section C is in the second year of composting is it will be the path.