A practice indigenous to the arid Sahel strip, they were reintroduced and brought to prominence again in the 1980s by Yacouba Sawadogo, an activist and expert farmer from Burkina Faso. He modified the traditional design into the multi-functional model used today.
Zaï pits deal with the related problems of aridity, erosion, and soil compaction, particularly on difficult-to-cultivate sloped land: crusted land exhibiting these features is locally called “Zippelle.”
During the dry season, pits are dug 15-20cm deep, and 20-50cm wide, and earth from the pits is arranged in a semicircular formation on the lower grade of the slope, to increase water retention. Organic matter such as raw compost, plant matter, or manure is added to the pits, creating a depressed, moist, water-retentive, nutrient-rich cavity in which trees or crops can be planted.
The raw compost in turn attracts termites, who burrow in the surrounding soil, loosening it to increase water and root penetration, and also digesting the raw organic matter in order to make the nutrients bioavailable to the plants.
Anschuetz et al. (2003)
Roose and Rodriguez (1990)
The World Bank reports that if done properly, this technique increase yields by 500%.  Combined with agroforestry strategies, like the planting of leguminous trees (traditionally, Acacia: see the “Great Green Wall”), it has the potential to reverse further soil erosion, compaction, desertification along the border of the Sahara.
I want to reinstate a respect for soil. We must touch the soil. How many times do we touch our mobile phone every day? Maybe 100 times. How many times do we touch the soil? Hardly ever. We must give dignity to peasants, farmers and gardeners.
We are all part of this healthy web of life maintained by soil. The Latin word humus means soil. The words human, humility and humus all come from the same root. When humans lose contact with soil, they are no longer humans.
These mysterious circles of bare ground are scattered along a 2000km stretch of desert, from Angola down to South Africa. They are typically surrounded by a thick patch of grass on their perimeter and are most frequent in the Namib desert, Namibia, shown in this image.
Their origin has remained a mystery until recent research, which analysed many years worth of satellite images.
We call it ‘back home’
knowing full well
that the majority of us
may never go back.
That we may spend
but a handful of weeks
in the tropic heat
and relentless traffic,
tolerating family members
we may have convinced
ourselves to have missed,
but very few will submit
to that final pull to return.
We know our land, our soil
as back home, but for many of us
it is only the home we left back,
the one we left so far behind
to be thrust into a lifelong search
of another, of another, of another.