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Maize: using compost and manure to grow more.
Maize is Kenya’s staple, and most of it is grown on tired, acidic soil. Compost and manure rebuild that soil, but they work best as part of a plan: right spacing, right timing, lime where it is needed, and some fertiliser alongside. This guide shows what that looks like.
The numbers that matter
KALRO, the Kenya Agricultural and Livestock Research Organization, gives these figures for maize. Fertiliser rates are per acre, as farmers buy them.
Why organic matter helps maize
Many maize fields in Kenya are acidic and low in organic matter. On such soil, fertiliser alone often disappoints. Our Soils of Kenya page explains why.
- It tames acidity. As manure and compost break down they release compounds that bind aluminium, which reduces how much of it is free to harm roots. KALRO recommends adding organic manure alongside liming.
- Lime where you need it. Lime is for soils whose pH is clearly too low, and a soil test tells you how much. Apply it well before planting and mix it evenly into the top 30 cm.
- Liming fertilisers are an alternative. KALRO lists some fertilisers with a liming effect, such as Mavuno and MEA Mazao, for acidic soils.
Lime rates depend on your soil’s measured acidity, so we don’t give a single figure here. Ask a KALRO office or an accredited soil laboratory to test a sample before you buy lime.
SOURCES: KALRO, MAIZE LAND PREPARATION; ESILABA (KALRO), “SOIL ACIDITY AND LIMING IN KENYA”, IFDC PRESENTATION (2018)
Timing, spacing and weeding
Timing
Plant within the first two weeks after the rains begin, once the soil is wet to at least 30 cm. Finish planting in a single day so the crop germinates evenly and closes its canopy together.
Prepare the land early, so weeds dry out and decompose before you plant.
Depth and seed
Place two to three seeds per hole. Plant 2 to 3 cm deep in well-drained highland and medium-altitude soils. In dry or sandy lowland and coastal areas, plant 5 to 10 cm deep.
Spacing
| Region | Maize alone (1 plant per hill) | Intercropped (2 plants per hill) |
|---|---|---|
| Highland | 75 × 25 cm — 53,333 plants/ha | 75 × 50 cm — 53,333 plants/ha |
| Medium altitude | 75 × 30 cm — 44,444 plants/ha | 75 × 60 cm — 44,444 plants/ha |
| Dry land and coast | 90 × 30 cm — 37,850 plants/ha | 90 × 60 cm — 37,850 plants/ha |
Weeding
The first four to six weeks after the maize emerges are when weeds do the most damage. Hand weed at least three weeks after emergence, then again when plants are knee-high. Pull up Striga (witchweed) early, before it sets seed. Dense legume cover crops such as lablab, velvet bean, sunhemp or desmodium can also suppress weeds.
SOURCE: KALRO, MAIZE LAND PREPARATION
Manure, compost and fertiliser, step by step
KALRO gives these as per-acre rates. Hectare equivalents are our conversions.
| Input | Rate | When |
|---|---|---|
| Farmyard manure, on its own | 4 tonnes per acre (about 10 t/ha) | Before planting, worked into the soil. |
| Farmyard manure with fertiliser | Half the recommended fertiliser rate | Manure before planting; fertiliser as below. |
| DAP | 50 kg per acre, one bag (about 125 kg/ha) | At planting. |
| CAN | 92 kg per acre, two bags (about 227 kg/ha) | Top dressing, when plants are knee-high. |
| Compost, in the hole | About a handful per planting hole | Mixed into the soil before the seed goes in. |
The DAP and CAN rates are the full rates. When you add manure, KALRO says to halve them. KALRO also notes that recommendations vary by agro-ecological zone and soil type, so check with your local extension office for the latest advice.
Putting compost in the hole
- Dig the holeMake planting holes about 10 cm deep, at your spacing (the compost leaflet uses rows 75 cm apart and holes 30 cm apart).
- Add compostPut about a handful of well-finished compost in each hole and mix it into the soil.
- PlantPlace the seed and cover it. Keep the seed from sitting directly on a lump of manure.
You can also scatter compost evenly over the field and work it into the seedbed before planting.
Plan your compost supply.
At 53,333 holes per hectare, even 50 g of compost per hole comes to more than 2.5 tonnes. That is our own arithmetic, not a recommendation. Work out how much compost you can make before you decide how much to apply.
SOURCES: KALRO, MAIZE LAND PREPARATION; AVRDC, “ENRICHED COMPOST FOR HIGHER YIELDS” (KENYA LEAFLET). HECTARE FIGURES CONVERTED FROM ACRES.
Organic inputs work, but they work best in combination
Here is what researchers found when they tested manure and organic matter on maize in Kenya.
| Treatment (central highlands, on-farm trials) | Maize yield (t/ha) | Net benefit (US$/ha) |
|---|---|---|
| No inputs | 1.8 | 52 |
| Farmyard manure alone | not given in text | 166 |
| Tithonia leaves alone | not given in text | 170 |
| Farmyard manure + half-rate N and P fertiliser | not given in text | 298 |
| Tithonia + half-rate N and P fertiliser | about 6.4–6.8 | 520 |
| Full-rate N and P fertiliser (60 kg/ha each) | 7.5 | 681 |
The researchers concluded that combining organic and inorganic inputs is the most feasible option for resource-limited smallholders. The best organic-plus-fertiliser mix (6.4 t/ha) did not differ significantly from full fertiliser (7.5 t/ha), while using half the fertiliser. “Tithonia” is the Mexican sunflower, a common roadside shrub whose leaves are rich in nutrients.
Other findings
- Western Kenya. In a KALRO slide of acid-soil trials, maize given no inputs yielded 0.53, and 2 tonnes of farmyard manure per hectare lifted it to 1.88. Manure with 20 kg of phosphorus as TSP gave 3.47. The slide’s unit labelling is unclear and it does not state the number of trials, so treat these figures as indicative.
- Long-term trials at Chuka and Thika. Under high-input management, organic maize yields matched conventional after a three-year conversion. Under low-input management at Thika, sole-cropped maize yielded three times more under conventional management, but maize intercropped with beans yielded about the same. Only the organic high-input system kept a positive soil nutrient balance, which the authors credit to leaving crop residues in the field.
SOURCES: PURDUE ISCO 12 CONFERENCE PAPER ON INTEGRATING ORGANIC AND INORGANIC INPUTS, KIAWANJA AND MARAGWA SITES, KENYAN CENTRAL HIGHLANDS; ESILABA (KALRO) / IFDC SLIDES (2018); FIBL MEDIA RELEASE ON THE KENYA SYSCOM TRIAL (2016)
Common mistakes
- Planting late. Waiting weeks after the rains start costs yield. Plant within two weeks.
- Skipping the soil test. On acidic soil, lime may be needed before other inputs pay off, and only a test will tell you.
- Liming just before planting. Apply lime well ahead and mix it into the top 30 cm.
- Using fresh manure. Fresh manure can burn crops and carry pathogens. Compost it or age it first (see what compost is).
- Relying on compost alone from day one. On badly depleted soil, small amounts of compost on their own may not match fertiliser in the first seasons. The trials above support combining the two while the soil recovers.
- Letting weeds run. The first four to six weeks are critical.
SOURCES: KALRO, MAIZE LAND PREPARATION; KALRO / IFDC LIMING SLIDES; TRIAL RESULTS ABOVE
Questions people ask
Can I grow maize with compost only?
You can, and the soil benefits, but on poor or acidic soil the trials show better yields when compost or manure is paired with some fertiliser. Start with the combination and cut back on fertiliser as your soil improves.
How much compost do I need per acre?
KALRO’s figure for farmyard manure is 4 tonnes per acre when used alone. For compost placed in planting holes, the guidance is about a handful per hole. Total quantity depends on your spacing and how much you can make.
Should I use manure or compost?
Either works, provided it is well decomposed. Fresh manure can burn seedlings, so compost or age it first.
Do I still need lime?
If your soil is acidic, yes. Manure helps by binding aluminium, but KALRO recommends manure alongside liming, not instead of it. Test the soil first.
Does intercropping with beans help?
At Thika, maize intercropped with beans yielded about the same under organic and conventional low-input management, while sole maize did not. Intercropping also changes the spacing, as the table above shows.
Where can I get a soil test?
Ask your county agriculture office or a KALRO centre, or use an accredited soil laboratory. Take samples from several spots in the field and mix them.
Want a plan for your own maize field?
We train farmers and groups to make compost from what they already have, and to use it where it pays.