Zaï Pit

A peasant innovation from Burkina Faso

Planting pits have long been used in the Sahel. The improved zaï that became known worldwide emerged around 1980 near Ouahigouya, in the Yatenga region of northern Burkina Faso, in a time of severe drought. Farmers began, as Chris Reij, Gray Tappan and Melinda Smale put it, to innovate out of despair: they dug the pits deeper and wider and concentrated nutrients and moisture in them. Yacouba Sawadogo, the most famous of them, began in 1979. He noticed that trees sprouted from the seeds in the manure, protected them, added seeds himself, and over the years created a forest of about twelve hectares. Where he had first counted four tree species, twenty years later he counted more than sixty.

The results for the region are remarkable. Together with contour stone bunds, at least 200,000 hectares on Burkina Faso's Central Plateau have been rehabilitated, according to the IFPRI study. In surveys from 2007, cereal yields with zaï were about 200 to 430 kilograms per hectare higher than on comparison fields, and the combination with stone bunds achieved the highest values. Hamado Sawadogo reported sorghum increases of 80 to 120 percent at an FAO workshop in 2017. Reij and colleagues also point out that most measurements cover only one to three years, and that the strongest evidence is that farmers keep digging the pits on their own initiative.

The limits are just as clear. Zaï is laborious: estimates range from about 300 to 650 hours of work per hectare, plus composting. It needs a lot of manure, which is scarce. And according to Roose, Kaboré and Guenat it works best with about 400 to 800 millimetres of rain. It bridges a dry spell of only two to three weeks, and only where the soil can store enough water; if it rains too much, water stands at the bottom of the pits and nutrients are washed out.

What fits the Mediterranean

Transferring zaï to Sardinia means separating the principle from the recipe. The recipe belongs to the Sahel: millet and sorghum, summer rains, flat crusted fields, termites. The principle is universal: on hard, degraded ground, water and organic matter are brought together at the exact point where a plant is to take root.

In the Mediterranean this principle suits the planting of young trees and shrubs on exhausted, compacted soils. A planting pit with compost at the bottom, placed where runoff arrives and covered with mulch, works in the same direction as the zaï. Two differences need attention. The rain falls in winter, when evaporation is low but soils on heavy clay can become waterlogged, so a pit in such soil should not become a bathtub. And in Mediterranean soils the work of the termites falls to other soil organisms, whose activity depends on moisture and organic matter just as much.

How Terra Humana understands it

For Terra Humana the zaï pit stands for something larger than a technique. It shows that the reversal of degradation does not have to come from outside, but can grow from the observation and courage of the people who farm the land. That Yacouba Sawadogo's pits brought forth a forest because seeds were in the manure is a lesson in how humus and life return together. It belongs to the same story as the regreening of the Sahel, and it is a reminder that water harvesting without fertility remains half the work.