Learn
Everything about compost and organic fertilizers, in one place.
Free, practical guides for anyone growing food or plants in Kenya and East Africa, from a kitchen garden to a commercial farm. Start with the basics below, then follow the links into detail.
What compost is, and why it matters
Compost is organic waste (crop residues, manure, kitchen scraps, leaves) that microbes have broken down into a dark, crumbly, earthy-smelling material.
It feeds the life in the soil, helps soil hold water and air, and releases nutrients slowly. It is not a quick-fix fertilizer. Its value is in rebuilding the soil that crops grow in.
In tropical soils, organic matter breaks down fast, so it has to be replaced often. Where it is not, soils lose structure, hold less water and respond poorly even to expensive fertilizer.
Studies in Kenya’s central highlands and western region found that heavy nitrogen fertilizer on acid, low-organic-matter soils did not lift maize yields above about two tonnes per hectare.
SOURCES: HEINRICH BÖLL STIFTUNG KENYA, “KENYA’S DIVERSE SOILS”
The main organic fertilizers and soil builders
They are not interchangeable. Each one does a different job, and each has a way it can go wrong.
| Type | What it is | Best used for | Watch out for |
|---|---|---|---|
| Compost | Decomposed plant and animal waste, dark and crumbly. | Building soil, planting holes, nursery mixes, mulch. | Immature compost can harm seedlings. Make sure it is fully matured. |
| Farmyard manure | Animal dung and bedding, aged or composted. | Bulk organic matter and nutrients for field crops. | Fresh manure can burn crops and carry pathogens. Compost or age it first. |
| Green manure | Crops such as legumes grown to be dug back into the soil. | Adding nitrogen and organic matter cheaply. | Needs land and a place in your rotation. |
| Bokashi | Food and other waste fermented in a sealed bucket with microbes. | Kitchen waste in small spaces. | It is fermented, not finished compost. Bury it or mix it into soil or compost and wait before planting. |
| Vermicompost | Castings from earthworms feeding on organic waste. | Seedlings, vegetables and high-value crops. | Worms need the right moisture and temperature. Hard to scale up. |
| Liquid feeds | Compost or manure “teas” and similar liquids. | A quick supplementary feed. | Hygiene matters. Keep them off edible parts of crops close to harvest. They don’t replace bulky organic matter. |
| Biochar | Charred plant material used as a soil amendment. | Improving structure and holding water and nutrients, best mixed with compost first. | Not a fertilizer on its own. Raw biochar can tie up nutrients. |
Six ways to make compost
The right method depends on your scale, your climate and how much time and labour you have.
Heap or pile
The simplest method. Layer browns and greens, keep it damp, and turn it. Good for most smallholders.
Read morePit or trench
Holds moisture well, which helps where rain is scarce. Harder to turn, and can waterlog in wet weather.
Read moreWindrow
Long rows turned by hand or machine. The standard for producing compost in volume.
Read moreBin or barrel
Compact and tidy for plots, compounds and balconies. Needs holes for air and attention to moisture.
Read moreBokashi
Ferments kitchen waste, including cooked food, in a sealed bucket. Produces pre-compost, not finished compost.
Read moreVermicomposting
Worms do the work. Excellent product for seedlings and vegetables. Suits small to medium volumes.
Read moreWhy compost and organic fertilizers are needed
Acid soils lock up phosphorus and make other nutrients harder for plants to reach. Low organic carbon weakens structure and water holding. Many Kenyan soils have both problems at once.
Counties with the largest share of acidic land
Compost is not a replacement for lime.
On strongly acid soils, KALRO guidance points to liming where soil pH is below about 5.2. Compost improves the soil’s buffering and biology, but a soil test should decide what you apply.
SOURCES: JOURNAL OF PLANT AND SOIL SCIENCES (2025); KALRO SOIL FERTILITY OVERVIEW (IFDC); NATION, “FARMERS TURN TO COMPOST AS SOILS WEAR THIN”
Compost and organic fertilizer by crop
Practical guidance on rates, timing and methods for the crops people in the region actually grow. We are publishing these one at a time.
MaizePotatoesKale and vegetablesTomatoesTeaCoffeeAvocadoKitchen gardens
Kitchen gardens is coming soon. Tell us which crop you want next.
Real farms, real numbers
Case studies from farms, schools, hotels and estates using compost and organic fertilizers, with what they did, what it cost and what changed. We will publish them here as we complete them.
Have you made compost work on your farm or institution? We’d like to tell your story, with your permission.
Prefer to learn in person?
We train farmer groups, households, schools and institutions to make compost from the waste they already have.