Making compost comes down to five things a farmer controls: roughly half dry brown material to half fresh green material, a heap big enough to hold its own heat, moisture at the wrung sponge level, air, and turning. Compost making on a Ugandan farm turns crop residues, weeds and manure into dark crumbly material in six weeks at the fastest, three months more often. The method below covers both the heap and the pit.
Why organic matter is worth the trouble at all, and the honest cost of using bulky slow sources, is argued out in the guide to organic nutrient sources on a Ugandan farm. This page picks up where that one stops. It is the procedure, and it assumes you are standing in the yard with a fork.
Browns and Greens: The Carbon to Nitrogen Ratio on a Ugandan Farm
The carbon to nitrogen ratio is a feeding instruction for the bacteria doing the work, not a number to memorise. Carbon is their food and their building material. Nitrogen is what they build proteins from. Feed them too much carbon and they run slowly because there is not enough nitrogen to grow on. Feed them too much nitrogen and the surplus leaves as ammonia gas, which is the smell of your fertilizer walking away.
FAO's work on farm composting methods puts the useful band for raw material at 25 to 30 parts carbon for every 1 part nitrogen, with anything from 20 to 40 still workable. Above 40 to 1 the process stalls and drags on. Below 20 to 1 nitrogen is wasted and the heap smells. Finished compost settles at about 10 to 15 to 1, which is why mature compost does not rob nitrogen from your soil the way raw sawdust does. Organic certification rules put the same instruction in writing from the other end, requiring a starting ratio between 25 and 40 to 1.
No smallholder measures this. What you do instead is sort material into two piles by eye. Brown means dry, woody, pale and light. Green means fresh, moist, soft and heavy. The African Organic Agriculture Training Manual, produced with the National Organic Agricultural Movement of Uganda among its collaborators, reduces the whole calculation to one rule: about half fresh green material and half dry material, with coarse woody material kept under a tenth of the heap. Too much fresh material and the heap packs down, goes sour and loses nitrogen. Too much dry material and the bacteria have nothing to eat, so nothing heats.
| Material | Carbon to nitrogen | Side |
|---|---|---|
| Sawdust | 100 to 500 | Brown |
| Cereal straw | 40 to 100 | Brown |
| Dry leaves | 30 to 80 | Brown |
| Cattle manure | about 19 | Green |
| Fresh grass | 15 to 25 | Green |
| Kitchen scraps | 15 to 20 | Green |
| Poultry manure | about 9 | Green |
The straw, sawdust, leaf and grass figures come from the Cornell Waste Management Institute's composting tables. The two manure figures are from FAO's table of manure composition and they are the same numbers used across our manure pages, so cattle at roughly 19 to 1 and poultry at roughly 9 to 1 hold wherever you meet them on this site. Read the ratio as a warning about quantity: poultry manure at 9 to 1 is the most concentrated green you will handle, and a heap built mostly of it will reek of ammonia within a day.
Farm Materials Worth Composting and What Each One Contributes
Uganda gives a farmer plenty on both sides. The trick is knowing which bin a thing belongs in, because several common materials do not behave the way their appearance suggests.
Where to Site a Compost Heap on a Ugandan Farm
Siting decides how much of your work survives the first heavy storm. Four things matter, and drainage matters most.
Pick level, well drained ground. On a slope, runoff walks through the heap and sieves the soluble nutrients out of the bottom of it, and you will never see them again. On flat ground that puddles, the heap sits in water and goes anaerobic from below. The Indore method's own siting rule is blunt about this: put the site high enough that rainwater cannot run into it during the wet season.
Put it in shade, either under a tree or under something you build. Shade cuts evaporation, which cuts watering labour, which is the cost that quietly kills most composting attempts. If you build a cover, build one you can lift off, because you want it on during heavy rain and off during light rain you would rather collect.
Site it near water and near the fields it will feed. Compost is heavy and the carrying is done twice, once with wet raw material and once with finished compost. A wheelbarrow path both ways is worth more than it sounds. And keep some distance between the heap and short season crops, especially vegetables, where the heap contains animal waste.
Building the Heap in Layers, With Air Channels and Soil
A heap heats because it is big enough to trap the warmth its own microbes make. Below a certain volume the heat escapes from the sides faster than it is produced, and the heap sits there cool and slowly rotting forever. The figure to hold onto is the one from the rapid composting work FAO reproduces: a pile needs to be at least 90 cm in each direction, and below about 80 cm the hot process will not start at all. That is the single most common reason a farm heap never warms.
Beyond the minimum, build for reach rather than for size. A width of about 1.5 m lets you work the heap from both sides without standing on it, and compaction is the enemy of air. Length is whatever you have material for, in runs of about 2 m. Height between 1 and 1.5 m. Sides almost vertical, top flat, and never trodden down. There is an upper limit too: once a pile passes roughly 2 m high or 4 m wide, air stops moving through the middle by itself and the centre goes anaerobic.
Moisture, Rain and Covering the Heap in Uganda
Composting wants the heap wet through, not wet at the bottom. FAO puts the working band at 40 to 65 percent moisture, best started at 50 to 60 percent and finishing near 30. Past 65 percent the water fills the air spaces and the heap goes anaerobic.
Nobody measures that either. The field version is the wrung sponge test. Take a fistful from inside the heap and squeeze hard. It should hold together and give up a drop or two at your knuckles. If water runs, it is too wet. If it falls apart dry and crumbly, it needs watering. Do the test at depth, not at the surface, because the outside of a heap in Ugandan sun is always drier than the middle.
Water roughly every third day, adjusted for what the sky has already done. Use a watering can or a sprayer rather than tipping a bucket, because a poured bucket runs off the crust and out of the bottom instead of soaking in. If the heap has gone too wet, open it up, mix dry organic material through it, or spread it in the sun for a few hours and rebuild.
Rain is the thing that ruins heaps in this country, and it ruins them two ways. Unprotected rain leaches the soluble nutrients straight down and out, so what is left is bulk without much fertilizer value. Persistent rain waterlogs the base and the heap turns sour and stops heating. That is what the topsoil cap, the dry grass cover and the liftable shade are all for. The compensation is that the wet season is by far the easier time to build a heap, because rain does your watering for you. Where water is genuinely short, build the heap during rainfall from material that is already wet.
The Heating Phase and When to Turn a Farm Compost Heap
The heat is not the sun. It is respiration. Millions of bacteria working through the easy sugars release energy faster than a heap that size can shed it, and the middle climbs. Mesophilic organisms do the first work between about 20 and 45 degrees Celsius, then hand over to thermophilic bacteria and fungi that run from 50 to 70 and higher. FAO records centre temperatures reaching 70 to 80 degrees within the first couple of days on a well built pile.
A properly built heap should be hot to the hand within 24 to 48 hours. If it is not, there are only three likely faults: too wet, too dry, or not enough green material. Check moisture first because it is the easiest to fix.
There is a ceiling too, not just a floor. Past about 71 degrees Celsius the fastest decomposers start dying off and the heap cools and has to restart, and FAO notes that piles above 75 degrees in warm climates have caught fire. Turning is how you let heat out.
On timing, turn after about three weeks, once the temperature has come down, not while the heap is still at its peak. Take the material from the top and the outside first and make it the inside of the new heap, because that cool outer shell has been doing nothing. Two or three turns in the early weeks is the norm, and nothing new gets added during a turn. A second turn comes three to six weeks later, and the compost is usable three to six weeks after that.
Turning frequency is the main lever on how long you wait. Daily turning of chopped material finishes in about two weeks and alternate day turning in about three. Turn at fifteen, thirty and sixty days and you are looking at four months. Never turn at all and you are looking at six to eight months, with the hygiene job left undone.
Two field tests replace a thermometer. The stick test is the one MAAIF's own extension material recommends: pull out the stick you drove in, and read it. Warm after two or three days means decomposition has started. Cold means it has not. A stick that comes out dry and whitish means the heap is dry inside, so turn it and water it properly. The smell test is the other. A sharp ammonia smell means too much nitrogen and nitrogen actively leaving as gas, and the fix is to work sawdust or another high carbon material into the part that smells. A sour, acid or rotten egg smell means the opposite problem: the heap is compacted or waterlogged and has gone anaerobic. Acid builds up in an airless heap and can pull the pH down to around 4.5, at which point the microbes more or less stop. Opening the heap and turning it brings the pH back on its own.
The Pit Method for Drier Parts of Uganda
Whether you build up or dig down is a genuinely regional decision, and it turns on water. In wetter districts a heap above ground drains and breathes and a pit fills up. In the drier north and northeast, a heap dries out faster than a farmer can water it, and a pit holds moisture so the same material composts on a fraction of the labour. The African organic manual states it plainly: in dry climates composting is mainly done in pits, to keep the material humid and save water and work.
The rule that keeps a pit from becoming a swamp is depth. The more arid the site, the deeper you dig, but never deeper than about 50 cm, because past that air cannot reach the bottom and you have built an anaerobic pit by accident. In a humid area, do not dig at all. Just loosen the ground so the material sits in contact with living soil. Keep the topsoil you dig out to one side, because it goes back into the heap.
Three named pit methods are worth knowing because their trade offs are different, and MAAIF's maize training manual for extension workers describes a three pit version of the same idea, sited in shade on a bed of twigs or stalks.
| Method | Best where | Time |
|---|---|---|
| Turned heap | Wet districts | 6 to 15 weeks |
| Turned pit | Dry districts | about 4 months |
| Mud sealed pit | Labour is short | 6 to 8 months |
The turned pit is the Indore version: about a metre deep and 1.5 to 2 m wide, filled within a week, turned at fifteen days, again fifteen days later and again a month after that, ready at around four months. A slurry of dung and material from an older pit is poured over each layer to seed it.
The mud sealed pit is the Bangalore version, and it is honest about what it gives up. Material goes in, the pit is plastered over with mud, and it is never turned. Labour is minimal, water use is minimal and nutrient losses are lower than in a turned heap. After a few weeks it goes semi anaerobic and stays that way, which means it does not reach or hold the temperatures that kill weed seeds and disease organisms, and it takes six to eight months. Use it for clean material when labour is the binding constraint. Do not use it for anything you need sterilised.
A variant worth knowing sits between the two: fill a pit, plaster it, let it sit four weeks until the mass settles, then break the plaster and turn the whole thing. That switch from airless to aerobic partway through is the Coimbatore method, run in a shaded pit of roughly 360 by 180 by 90 cm, built up to about 60 cm above ground level and moistened to the wrung sponge point as it goes in.
Tithonia and Lantana as Compost Accelerators on Ugandan Farms
Two shrubs that grow wild along Ugandan boundaries and roadsides are among the best free nitrogen you can put in a heap. Tithonia diversifolia, the yellow flowered Mexican sunflower, is recorded across Uganda and is the stronger of the two. Work by ICRAF on East African samples puts the nutrient content of its green leaves at about 3.5 percent nitrogen, 0.37 percent phosphorus and 4.1 percent potassium on a dry matter basis, with nitrogen ranging from 3.1 to 4.0, phosphorus from 0.24 to 0.56 and potassium from 2.7 to 4.8. That nitrogen figure matches nitrogen fixing legume shrubs, and the phosphorus and potassium figures beat most of them. Lantana camara green leaves came out lower in the same comparison at about 2.8 percent nitrogen, 0.25 percent phosphorus and 2.1 percent potassium, which still makes it a useful green.
The part that matters in practice is cut it green. In the same western Kenya work, tithonia leaves that had senesced on the plant dropped to 1.1 percent nitrogen against 3.2 percent for green leaves from the same locations, and litter already lying under a tithonia canopy tested at 1.3 percent. Stems came in at 0.8 percent. Leaves are only about 15 to 17 percent of the plant's above ground bulk but they carry 35 to 40 percent of its nitrogen and phosphorus. Sweeping up dropped leaves gets you a third of the value of cutting fresh ones.
Volume is the limit. A boundary hedge of pure tithonia yields roughly a kilogram of leaf and tender stem per metre per year on a dry weight basis, so fifty metres of hedge gives something like fifty kilograms of dry material in a year. Treat tithonia as the accelerator in the green half of a heap, not as the heap. Composting trials on tithonia rich piles found that piles built almost entirely of it spiked and then cooled off quickly, while piles where it made up around half the material held the high temperature range for considerably longer. Half and half is the useful reading.
Two handling notes. Tithonia has no thorns but the cut material is sticky and smells sharp, so cut it with a panga into a sack rather than carrying armfuls. And tithonia contains compounds that hold back plant growth, which is a further reason to compost it rather than pile fresh cuttings around seedlings. Lantana is a declared problem plant on grazing land across much of the region, so cutting it for a heap puts material you are clearing anyway to work. Take the leaves and soft growth. Woody lantana stems belong with the material you dry and burn, not in a heap you want to finish this season.
What Not to Put in a Compost Heap, Including Sprayed Plant Material
The exclusion list is short and every item on it is there for a concrete reason.
Plant material recently sprayed with a herbicide is the one that catches careful farmers. Some herbicide active ingredients persist through the composting process, come out in the finished compost and damage the next crop it touches, particularly beans, tomatoes and other sensitive vegetables. There is no interval this page can give you, because the interval depends on the active ingredient and it is stated on the product label. The label is the operative authority, and your district extension officer can read it with you. Our page on how herbicides work and what they leave behind covers the active ingredient classes. Until you have checked, keep sprayed residue out of the heap.
Diseased or pest infested plant material stays out of any heap you are not confident will heat right through. A heap that genuinely reaches the thermophilic range destroys most pathogens; a cold heap simply stores them and spreads them back over your field. Material from a crop you lost to a disease is better burned than composted, and that costs you nothing but the ash, which you can put back in thin layers.
Weeds that have already set seed, and persistent perennial weeds, need the same caution. The African organic manual's instruction for persistent perennial weeds, the couch grass and star grass class of problem, is to spread them in the sun until dead, or burn them, and put the dried material or the ash in the heap rather than the live plant. Weed seeds in cow manure are a related problem and they are dealt with on the page about using cow manure to rebuild tired soil.
Plastics, rubber, leather, textiles, metal and glass do not compost. They just come out again in smaller pieces, spread across your soil, permanently. Sort them out at the collection stage, not at the spreading stage. Manure from dogs and cats stays out too, since carnivore waste carries parasites that a farm heap is not reliable at destroying. Thorny and prickly material is excluded for a simpler reason: somebody has to turn this heap with their hands.
Ash is the one item the sources disagree on. The Indore and Ecuador composting methods both include wood ash in the build, while the rapid composting method tells you to keep stove and fireplace ash out entirely. The resolution is quantity and origin. Thin scatterings of clean wood ash between layers are useful for potassium; heavy ash raises the pH and drives nitrogen off as ammonia; and ash from a fire that has burned treated timber, plastic or general rubbish is not wood ash and does not belong anywhere near a food crop.
Heap Temperature, Weed Seeds and Disease Control
This is where composting either earns its reputation or fails quietly, so it is worth being exact about temperatures.
FAO's figures give two separate thresholds, and the gap between them matters. Pathogens are normally destroyed at 55 degrees Celsius and above. Weed seeds need 62 degrees. A heap that got warm but not hot has done half the job and only half. It has probably dealt with the disease organisms and left you a field's worth of live seed.
Certified organic systems do not take a farmer's word that a heap got hot, so they write the requirement down as a band plus a duration: the material must be held between 55 and 77 degrees Celsius, for three days where the pile is covered or aerated, or for about fifteen days in a turned windrow given at least five turnings. The same rule fixes the starting carbon to nitrogen ratio between 25 and 40 to 1, which is the other half of the same instruction, because a heap outside that band will not reach those temperatures in the first place.
Turning is what converts a hot core into a hot heap. The outside of every pile stays cool no matter how fierce the middle gets, so seed and spores sitting in that outer shell survive untouched. Moving the outside material to the inside at each turn is the whole point of the exercise, and it is why five turnings appear in the certification wording rather than one. A heap that is never turned sterilises only its own centre.
The plain admission a farmer needs: a cold heap does not kill weed seeds or pathogens. If your heap sat in the corner of the compound for five months without ever being hot to the hand, what you have is aged material, which is better than fresh and still carries live seed. That is an acceptable product for a maize field and a poor one for a vegetable nursery. If you are selling into a certified chain, the stick test is not enough and you will need a real compost thermometer and a written record of the readings.
How to Tell When Compost Is Ready to Apply to the Soil
Four signs, and you want all four before you spread it.
Colour and texture. Blackish brown to dark brown, crumbly, uniform. Nothing that went in should still be identifiable: no recognisable grass, no leaves, no animal droppings. Woody stalks and stems are the exception and may well still be there, because they take longest. Screen the heap through chicken wire of about 2.5 cm mesh and throw the oversize into your next heap.
Smell. Fresh earth. That is the whole test. Any ammonia note means nitrogen is still being lost and it is not finished. Any sour or sulphurous note means part of the heap went anaerobic and needs turning and more air, not spreading.
Temperature. No heat left, and, the more reliable version, turning it no longer makes it reheat. That is the moment FAO uses to mark the end of active composting and the start of curing.
Volume. It should have lost roughly half the bulk it started with. A heap that has barely shrunk has barely composted.
On timing, the sources disagree and you should know by how much. MAAIF's maize training manual describes a heap turned at three weeks and ready three weeks after that, while the same manual elsewhere says crop residues and household waste take two to three months. The African organic manual's schedule works out at roughly nine to fifteen weeks for a turned heap. An unturned mud sealed pit takes six to eight months. The honest planning figure for a Ugandan farm heap turned two or three times is about three months, with six weeks achievable only on chopped material turned often. Let the four signs decide rather than the calendar.
Do not store finished compost longer than you must. The longer it sits, the more of its fertilizer value it loses, though its value for soil structure keeps rising. If the planting season is still off, leave the heap where it is, covered, in shade, capped with about 10 cm of topsoil. Compost that is not quite finished still has a use: spread it as mulch between crops or around trees under a thin layer of dry grass, and it will finish on the ground. Before you decide how much to put where, the case for testing your soil first is worth reading, because compost and a bag of fertilizer answer different questions.
How Much Compost a Heap Yields Per Acre
This is the calculation that decides whether composting is worth your labour, and almost nobody does it before starting.
The governing fact is simple: composting halves the volume. Two tonnes of raw material make about one tonne of compost. Everything else follows from that.
That arithmetic explains two pieces of advice that otherwise sound arbitrary. First, compost applied to grain crops often does not repay the labour, while the same compost on tomatoes, onions or another cash crop usually does. Second, targeted placement beats broadcasting when you have a limited quantity: into the planting holes for transplanted crops, along the sowing rows for sown crops, along the drip line for a tree crop rather than at the trunk, and never ploughed in deeply. Spreading three quarters of a tonne thinly over an acre achieves very little; putting it in the holes of a quarter acre of tomatoes achieves a lot.
Read the 4 to 6 tonnes as MAAIF's figure for maize and nothing wider. There is no single verified Ugandan compost rate that covers every crop and soil, and the bulk and labour trade off that comes with every organic source is the reason. If you are pairing compost with a bag, the timing and sequencing for a specific crop sits in the maize fertilizer application guide.
Compost Making Questions Ugandan Farmers Ask
How long does compost take to be ready in Uganda? Plan on about three months for a heap turned two or three times. Six weeks is achievable if the material was chopped small and you turn it every two or three days, and daily turning of finely chopped material can finish in around two weeks. A pit sealed with mud and never turned takes six to eight months. Warm weather helps throughout, which is why Ugandan heaps run at the faster end of the published ranges.
What does it cost to make compost? No cash for the material, which is the point of it. The real costs are labour, water and carrying, and labour is the one farmers underestimate: collecting, chopping, building, watering every third day and two or three turns of a heap that weighs over a tonne. Tools are a hand hoe, a panga, a spade or forked hoe, a watering can and ideally a wheelbarrow, all of which you probably own. A compost thermometer is the only thing you might buy and only a farmer selling into a certified chain needs one. If you are comparing composting against buying nutrients, look at what suppliers are asking for fertilizer in Uganda at present, because the comparison changes with the season and the district.
Why does my heap never get hot? Almost always one of four things. It is too small, and a heap under about 90 cm in every direction cannot hold its own heat. It is too dry, so squeeze a handful and check. It is too wet and has gone airless, in which case it will smell sour. Or it has too little green material, so there is not enough nitrogen for the bacteria to multiply on. Fix moisture first, then add fresh green material, then rebuild bigger if neither works.
Can I make compost during the dry season if water is short? Yes, and a pit is the way to do it, because it holds moisture where a heap loses it. Dig no deeper than 50 cm, site it in shade, and cover it. If water is really tight, the standard advice from organic training material in the region is to spend it on the compost rather than on irrigation, since compost raises the soil's water holding capacity and pays that water back later. The alternative is to build during the rains from material that is already wet.
Is it safe to compost weeds that have already gone to seed? Only in a heap you know gets hot, and hot here means 62 degrees Celsius, which is above the 55 degrees that deals with disease organisms. Even then, seed sitting in the cool outer shell survives, so it only works if you turn the heap and move that outside material into the middle. If you are not confident, dry the seeding weeds in the sun until dead or burn them, then put the dried material or ash in the heap.
Can I put wood ash in the compost heap? Thin scatterings between layers, yes, and it supplies potassium. Heavy ash pushes the pH up and drives nitrogen out as ammonia gas, so you lose the nutrient you were working hardest to keep. Ash from a fire that burned treated timber, plastic or household rubbish is a different material and should stay out.
Can I use compost that still has stalks and stems in it? Yes, if everything else looks and smells finished. Sieve it through wire mesh of about 2.5 cm and put the oversize pieces into the next heap. Or use the unscreened material as mulch between crops, covered with a little dry grass, and let it finish on the ground rather than in the heap.
Do I need to add a commercial compost starter? No. The organisms that do the work are already present on any plant material you collect, and nothing needs to be bought to make a heap decompose. Fresh animal manure is the cheapest and most effective accelerator there is, tithonia and lantana leaves are next, and turning the heap more often does more than any product. Rock phosphate is the one addition worth considering on soils that lock up phosphorus, because phosphorus added to the heap reaches the crop more readily than phosphorus added straight to that kind of soil.
Composting costs labour rather than cash, so the decision it really competes with is whether to buy nutrients in a bag instead. Prices for fertilizer, manure and packaged organic products move with the season and differ by district, so it pays to ask several input suppliers in your area what they are charging and what nutrient content they are declaring before you commit either way. Your district agricultural extension officer can tell you which organic material is realistically available near you, confirm whether anything you have sprayed is safe to compost, and read a herbicide label with you. Everything else on inputs sits in the farm inputs section.