Practical skills · Course 2 of 8
Soil and plant health
6 modules · 90 minutes · Intermediate · Free
Healthy plants come from healthy soil. This course teaches you to read your soil, understand what your plants need, identify and manage common problems, and build long-term soil fertility using indigenous agroecological principles. No synthetic chemistry required — just observation, knowledge, and good practice.
By the end of this course you will be able to
Soil is alive
A single teaspoon of healthy agricultural soil contains more living organisms than there are people on earth.
Bacteria, fungi, protozoa, nematodes, earthworms, beetles, and hundreds of other organisms form a web of relationships that processes organic matter, releases nutrients, builds soil structure, suppresses disease, and regulates water movement.
This is not a metaphor — it is measurable biology.
When you add synthetic fertilisers repeatedly, when you till deeply and frequently, when you leave soil bare and exposed, you are not just managing chemistry. You are disrupting an ecosystem.
The short-term yield gains from synthetic inputs come at the cost of long-term soil health — and farmers increasingly find that they need more and more input to maintain yields on soil that has become less and less alive.
Agroecological farming — the approach that underpins everything Shiriki does — works with soil biology rather than substituting for it.
The four things healthy soil needs
How to read your soil — a simple field assessment
Before you add anything to your soil, observe it. These simple observations take 15 minutes and give you more useful information than a basic laboratory test.
Colour: Dark brown to black soil is rich in organic matter. Light brown or grey soil is depleted. Red soil indicates iron minerals and is common across Gauteng.
Texture: Sandy soil falls apart. Clay soil stays in a ball and feels sticky when wet. Loam holds its shape briefly then crumbles.
Earthworms: Dig a 30cm × 30cm hole, 20cm deep. More than 10 earthworms indicates healthy soil biology.
Smell: Healthy soil smells earthy and fresh — the smell of geosmin produced by actinobacteria.
Compaction: Push a metal rod or pencil into the soil. If it stops at 5–8cm, you likely have compaction problems restricting root growth.
Check your understanding
Module 1 · 3 questions + reflection
Conduct the soil assessment described in this module on the land you are farming or planning to farm. What did you find?
What does it tell you about the current health of your soil?
If you have been farming with synthetic fertilisers, how does the information in this module change the way you think about soil management?
What composting is — and why it works
Composting is the managed decomposition of organic materials by microorganisms — bacteria and fungi — into stable humus.
This process releases nutrients in plant-available forms, builds soil organic matter, improves soil structure, and inoculates your soil with beneficial microorganisms.
Well-made compost is not just a fertiliser — it is a complete soil amendment that improves every aspect of soil health simultaneously.
The basic compost recipe — browns, greens, air, water
The ideal compost pile — step by step
Choose a shaded, well-drained area. Build at least 1m × 1m × 1m for proper heat generation.
Layer browns, then greens, and add a little soil or finished compost to introduce microbes.
Water each layer and maintain moisture throughout.
Turn after 1 week, then every 2 weeks until finished.
A hot compost pile reaches 55–65°C and kills weed seeds and pathogens.
Finished compost is dark, crumbly, and smells earthy.
Indigenous crop materials that make excellent compost
Start a compost pile using browns, greens, and water. Build in layers and turn weekly.
Observe temperature, smell, and texture changes over time.
This is how you begin making your own soil fertility.
Check your understanding
Module 2 · 3 questions + reflection
What materials do you have locally for composting?
How much fertiliser cost could you replace with compost?
What waste around you can become soil fertility?
Why rotation works
Growing the same crop in the same soil season after season depletes specific nutrients, builds up specific pest and disease populations, and gradually reduces yield.
Rotation disrupts these cycles. A legume after a grain feeds nitrogen back into the soil. A leafy green after a root crop uses a different part of the soil profile.
Diverse rotations keep soil biology diverse and productive.
The Shiriki four-bed rotation
Then the cycle repeats. Each bed moves through all four stages over four seasons.
The result is a self-sustaining fertility cycle that requires minimal external inputs.
Intercropping — growing more on the same land
Intercropping means growing two or more crops in the same bed at the same time.
Done well, it increases total yield per square metre, suppresses weeds through competition, and creates beneficial ecological relationships between plants.
Traditional African farming was intercropping — not monoculture — by default.
Proven indigenous crop intercropping combinations for Gauteng
Sketch your current growing area — even a small backyard plot.
Divide it into four rough sections and assign each section a place in the four-season rotation.
Which section would you start with legumes this season? What would you plant there next season?
Planning rotation on paper before planting helps prevent years of soil depletion.
Check your understanding
Module 3 · 3 questions + reflection
Looking at the four-bed rotation model — which part of it would be most challenging to implement on your current growing space?
What would you need to make it work?
Have you ever seen traditional African intercropping in practice — in your family's garden, at a community plot, or anywhere else?
What crops were grown together? Did it work?
The most common nutrient deficiencies in indigenous crop production
In indigenous crops: Particularly visible in morogo, jute mallow, and spider plant.
Fix: Apply compost, well-rotted manure, compost tea, or diluted urine. Long-term: add nitrogen-fixing legumes to the rotation.
Fix: Bone meal, rock phosphate, and compost rich in organic matter. Healthy mycorrhizal fungi also improve phosphorus uptake.
Fix: Wood ash, compost, banana peels, or kelp meal where available.
Common cause in Gauteng: High soil pH making iron unavailable to plants.
Fix: Improve soil organic matter with compost and test pH before adding iron supplements.
Diagnostic walk
Go to your growing beds and spend 15 minutes examining your plants closely.
Using the signs described in this module, identify whether any plants show signs of nutrient deficiency.
Photograph what you see for future reference.
Before deciding on a fix, ask:
When did I last add compost? What crop was in this bed before? Is the soil pH likely to be high or low in this location?
These answers guide intervention more reliably than guessing.
Inspect at least three different crops growing near you this week.
Compare leaf colour, stem strength, growth rate, and any signs of yellowing or scorching.
Record what you notice and what you think the plants may be communicating about soil health and fertility.
Check your understanding
Module 4 · 3 questions + reflection
Have you noticed any of the deficiency symptoms described in this module in your own growing experience?
Looking back, what do you think was the cause — and what could you do differently?
How does understanding plant nutrition change your relationship to compost and soil organic matter?
What does it tell you about the true value of well-made compost?
The first principle: prevention over cure
Healthy plants in healthy soil are significantly more resistant to pest and disease pressure than stressed plants in depleted soil.
Before you reach for any spray — biological or chemical — ask whether the pest problem is a symptom of an underlying stress: water stress, nutrient deficiency, overcrowding, or poor air circulation.
Addressing the stress often resolves the pest problem more effectively than the spray itself.
Common pests affecting Shiriki crops — identification and management
Affected crops: Jute mallow, cowpeas, lablab, morogo, and okra.
Management: Strong water spray, encouraging ladybirds, neem oil spray (5ml neem oil in 1 litre water with dish soap), and removing heavily affected growth.
Affected crops: Amaranth, morogo, and cowpea leaves.
Management: Remove damaged leaves, apply neem spray early, and improve crop rotation practices.
Management: Grow slenderleaf (Crotalaria) and marigolds in rotation to suppress nematode populations. Crop rotation also reduces build-up.
Cause: Soil-borne fungi in waterlogged, poorly drained conditions.
Management: Avoid overwatering, use well-draining media, water in the morning, and apply wood ash or fine sand around seedlings.
Slenderleaf's nematode suppression
Swahili name: Marejea
Regional name: Mitoo (Tanzania)
Agroecological function: Suppresses Meloidogyne spp. (root-knot nematodes) in affected beds.
A note on chemical pesticides
Shiriki's approach is agroecological — synthetic pesticides are not used as a first response to pest pressure.
Synthetic pesticides often kill beneficial insects along with pest insects, disrupt soil biology, and create pesticide-resistant pest populations over time.
Biological and cultural interventions are most effective when applied consistently and early.
Reserve chemical interventions for genuine emergencies only, and choose the most targeted, least broad-spectrum option available.
Visit your growing space this week and inspect plants carefully for signs of pests or disease.
Look under leaves, inspect stems, and check soil moisture and airflow around plants.
Record what you observe and identify whether the problem may be linked to stress factors such as overcrowding, poor drainage, or nutrient imbalance.
Check your understanding
Module 5 · 3 questions + reflection
Think about a pest or disease problem you have experienced on your growing space.
Looking back through the lens of this module — was there an underlying plant stress that made the crop more susceptible?
What would you do differently now?
What is your current approach to pest management? Which parts of the integrated approach described in this module would you be willing to try first?
Understanding water in indigenous crop systems
One of the most important advantages of indigenous crops is their water efficiency. Sorghum uses water more efficiently than maize at every growth stage. Bambara groundnut produces reliably in low-rainfall conditions. Spider plant and morogo recover quickly from water stress. Even amadumbe — which loves moisture — can survive significant dry spells once the corm is established underground.
But water efficiency in the crop is only one part of the equation. How you manage your soil determines how much of the water you apply actually reaches plant roots — versus evaporating from the soil surface, running off, or sitting in poorly drained beds.
Mulching — the most impactful single action
Mulch is any material laid on the soil surface around plants: dry leaves, straw, shredded newspaper, wood chips, dried grass. It does five things simultaneously:
• Reduces water evaporation from the soil surface (by up to 70%)
• Moderates soil temperature
• Suppresses weeds
• Prevents surface crusting that reduces infiltration
• Decomposes into organic matter over time
Apply 5–10cm of mulch around your plants, keeping it a few centimetres away from the base of stems (to prevent rot). Replenish as it decomposes. This single practice can reduce your water requirement by 30–50% in Gauteng's dry months.
Watering techniques — when and how
Water early morning: Reduces evaporation loss. Leaves dry during the day, reducing fungal disease risk. Evening watering leaves foliage wet overnight — ideal conditions for fungal disease.
Water deeply and less frequently: Frequent shallow watering encourages shallow root systems. Deep, infrequent watering encourages roots to grow down — making plants more drought-tolerant.
Direct to the root zone: Drip irrigation or targeted hand watering at the base of plants is far more efficient than overhead sprinkler watering, which loses 30–50% to evaporation before it reaches the soil.
Read the plant, not the calendar: Check soil moisture at 5–10cm depth before watering. If it is still moist, wait. If dry, water deeply.
Rainwater harvesting on a small scale
In Gauteng, summer rainfall (November–March) is significant — often 600–800mm annually. Capturing even a fraction of this for dry-season use transforms a water-constrained operation.
JoJo tanks connected to gutters on a greenhouse, tunnel, or any roofed structure can collect hundreds of litres per rainfall event.
A 2,500-litre JoJo tank connected to a 20m² tunnel roof can fill completely in a single moderate rainfall. At R2,500–4,000 installed, a JoJo tank pays for itself in water savings within one dry season.
Water audit exercise
For one week, record: how many litres of water you apply to your growing space each day, at what time of day, and how.
At the end of the week, ask:
• How much water went into the root zone versus evaporated or ran off?
• Is there mulch on all your beds?
• Are you watering in the morning?
• Are you watering deeply or shallowly?
Identify the one change that would most reduce your water use without reducing plant health.
Check your understanding
Module 6 · 3 questions + reflection
Water cost and availability is one of the biggest constraints for small-scale farmers in Gauteng. After completing this module, what is the single most impactful change you could make to your water management this week?
Is there a rainwater harvesting opportunity on your current growing space? What would it cost to set up a basic JoJo tank collection system, and what would it save you annually?