Soil Conservation With Trees: What Actually Works
Stop the cause → slow the water → cover the ground → then plant trees.
Planting into an active gully or an overgrazed slope is the most visible waste of money in soil conservation. Moving water removes seedlings along with the soil, and livestock remove whatever survives.
Do These in Order
| Step | What it means | Why first |
|---|---|---|
| 1. Stop the cause | Grazing control, fire management, ending cultivation on the steepest ground | Nothing else holds while the cause continues |
| 2. Slow the water | Contour bunds, terraces, check dams, trenches | Fast water removes anything you plant |
| 3. Cover the ground | Grasses, cover crops, mulch, litter | Erosion starts at the ground layer, not the canopy |
| 4. Plant trees | Contour lines, hedgerows, scattered farm trees, block planting on the worst ground | Trees hold soil long-term but do not stop active erosion on their own |
Everything Follows the Contour
- Tree lines, hedgerows, grass strips and trenches all run along the contour, never up and down the slope.
- A line running down the slope becomes a channel and accelerates erosion — the exact opposite of the intent.
- Combine woody and grass strips. Trees alone leave gaps at ground level where soil actually moves.
- Closer spacing between contour lines on steeper ground. The steeper the slope, the shorter the run of water you can allow.
- On terraced land, plant along terrace edges — it stabilises the structure and produces fodder and stakes at the same time.
Gullies Need Structure Before Planting
Treat the head, not the middle
- A gully erodes backwards from its head. Work in the middle achieves little while the head keeps cutting.
- Stabilise the head first, then work down.
- Divert water away from the head where possible — often the single most effective intervention.
- Check dams down the channel slow flow and trap sediment, which builds the bed back up.
- Plant only once the channel is stable. Vegetation holds what structure has already secured; it does not secure it in the first place.
Erosion on your land? Structure comes before planting, always.
Species That Do the Work
| Job | Type of species | Examples |
|---|---|---|
| Contour hedgerows | Fast, coppicing shrubs that tolerate repeated cutting | Calliandra calothyrsus, Leucaena, Gliricidia sepium |
| Ground-layer strips | Dense tussock grasses | Vetiver, Napier and locally appropriate grasses |
| Gully edges | Deep-rooting, tolerant of disturbance | Locally occurring riparian and pioneer species |
| Scattered farm trees | Nitrogen fixing, light canopy | Faidherbia albida, Albizia, Grevillea robusta |
| Slope stabilisation blocks | Deep rooting, dense cover | Locally proven species; avoid heavy water users near springs |
Trees That Rebuild Fertility
Erosion is only half the problem. Degraded soil is also usually exhausted, and trees can address that directly.
- Nitrogen-fixing species add nitrogen biologically. Faidherbia albida is particularly valuable on cropland because it sheds its leaves during the growing season, so it fertilises without shading the crop.
- Deep roots recycle nutrients from below the reach of annual crops, depositing them at the surface as litter.
- Litter and mulch rebuild organic matter, which improves both water-holding capacity and structure.
- Prunings from hedgerows can be applied as green manure — the basis of alley cropping systems.
More on integrating these into working farmland in agroforestry.
Four Mistakes
- Planting into an active gully. The most visible waste of money in this field.
- Lines running down the slope instead of along the contour, which accelerates erosion.
- Trees without ground cover. Erosion happens at the ground layer; a canopy above bare soil does not stop it.
- Ignoring grazing. On most degraded slopes this is the actual cause, and planting without addressing it repeats the original failure.
Frequently Asked Questions
What trees are best for stopping soil erosion?
Fast, coppicing shrubs for contour hedgerows — calliandra, leucaena and gliricidia are the standard choices — combined with dense tussock grasses such as vetiver in the ground layer.
Trees alone leave gaps at ground level where erosion actually starts, so the woody and grass components work together rather than as alternatives.
Can I plant trees to fix a gully?
Not as the first step. A gully erodes backwards from its head, and vegetation will not hold ground that moving water is actively cutting.
Stabilise the gully head, divert water away from it where possible, install check dams down the channel, and plant once the channel is stable.
Why do trees have to be planted on the contour?
Because a line running down the slope becomes a channel and concentrates water, accelerating erosion — the opposite of what was intended.
Contour lines intercept and slow water across the slope. The steeper the ground, the closer together the lines need to be.
Which trees improve soil fertility?
Nitrogen-fixing species. Faidherbia albida is particularly valuable on cropland because it drops its leaves during the growing season, fertilising the soil without shading the crop.
Deep-rooting species also recycle nutrients from below the reach of annual crops, and hedgerow prunings can be applied as green manure.
Will planting trees stop erosion on overgrazed land?
Not on its own. If grazing pressure continues, livestock remove the seedlings and the ground stays bare.
Grazing management has to come first. This is the most common reason erosion-control planting fails, and it is a management question rather than a technical one.
Stop the Cause Before You Plant
Planting into active erosion or ongoing grazing repeats the failure. One assessment gets the sequence right.
Over a decade establishing, measuring and managing eucalyptus, pine and indigenous plantations across Uganda. Based in Wakiso, Kampala. Reviewed and updated September 6, 2026.
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These apply the same way in any country.
