What it is
Zaï (or tassa in Niger) are small planting pits dug into hard, degraded dryland soil — each hole perhaps 20–30 cm across and 10–20 cm deep — into which a handful of manure or compost is placed before the rains. When the rain comes, each pit catches and holds water that would otherwise run off the crusted surface, the manure draws termites that tunnel and loosen the soil below, and a few seeds of sorghum, millet, or a tree are sown into that pocket of moisture and fertility.
It is one of the most celebrated techniques in all of dryland farming, because it does something that seems almost impossible: it brings abandoned, rock-hard, barren land back into production, using nothing but a hoe, manure, and labour.
The problem it solves
Across the Sahel, decades of drought, overgrazing, and cultivation had left vast areas of zipellé — land so hardened and capped that rain simply ran off it, taking the little topsoil with it. Nothing would grow, and the land was abandoned. This is the extreme end of the erosion and desertification that threatens all drylands.
The zaï pit attacks this on several fronts at once:
- the pit breaks the crust and creates a rough surface that stops water running off;
- it harvests rainfall into a concentrated pocket, so a plant gets the benefit of far more than the rain that falls on its own small area;
- the manure feeds the plant and, crucially, attracts termites, whose tunnels break up the hardpan below the pit and let roots and water penetrate deeper;
- and the pits trap wind-blown seeds, leaves, and soil, so organic matter accumulates in them over time.
The revival
Zaï is an old technique that was revived and spread in Burkina Faso in the 1980s, above all through the work of a farmer named Yacouba Sawadogo — "the man who stopped the desert" — who experimented with deeper, manure-filled pits and taught the method across the region. Combined with stone contour bunds to slow runoff across whole slopes, zaï has rehabilitated hundreds of thousands of hectares, raised the water table in places, and turned famine-prone districts into grain exporters. It is a rare, genuinely successful, farmer-led land restoration movement.
Digging and using them
The pits are dug in the dry season, when the soil is being broken by hand is hardest but labour is available — spreading the work before the rains. They are set out on a rough grid, often 70–80 cm apart, giving perhaps 10,000–25,000 pits per hectare. Excavated soil is placed on the downslope side to form a small lip that catches still more water.
Manure (a few handfuls per pit, up to a couple of tonnes per hectare) is the active ingredient — it feeds the crop and the termites. After sowing, the pits are used again for several seasons, and often trees are allowed to regenerate in them, so a zaï field gradually becomes an agroforestry parkland. The technique is labour-intensive, which is its main limit, but on land that produced nothing at all, the return is transformative.
Zaï belongs to the wider family of dryland rainwater harvesting that includes the half-moon microcatchments and contour bunds — all of them ways to make the most of scarce, erratic rain by catching it where it falls.
See also
- Half-Moons and Microcatchments the larger crescent version of the same idea
- Contour Bunds the slope-wide partner technique
- Rainwater Harvesting Basics the principles behind catching runoff
- Dryland Restoration the barren ground zaï reclaims
- Assisted Regeneration letting trees return in the pits
- Soil Water Storage how the pits hold moisture for the crop