permaculture

["Lawrence F. London, Jr." <venaurafarm@bellsouth.net>]

*Planting pits*

An example of the rapid restoration of productivity of degraded land is
an indigenous method in the Sahel region called “zaï” (FAO, 1994).
During the dry season, farmers dig out pits 15 cm deep and 40 cm in
diameter every 80 cm, tossing the earth downhill. The dry desert
Harmattan wind blows various organic residues into the excavated pits.
The organic materials are consumed quickly by termites, which excavate
tunnels through the crusted surface, allowing the first rains to soak
down deep, out of danger of direct evaporation.

Two weeks before the onset of the rains, farmers spread one or two
handfuls of dry dung (1- 2.5 tonnes/ha) in the bottom of the pits and
cover it with earth to prevent the rains from eroding away the organic
matter.

Millet is sown into the pits at the onset of the rainy season. As the
first rains wash over the surface crust (of the degraded land), the
basins capture this runoff (enough to soak a pocket of soil up to 1 m in
depth). The sown seeds germinate, break up the slaked surface crust and
send roots down to the deeper stores of both water and nutrients
(recycled by the termites).

At harvest time, stalks are cut at a height of 1 m and left /in situ /to
reduce wind-speed and trap windborne organic matter. In the second year,
the farmer either digs new basins between the first ones and dresses
them with manure, or pulls up the stubble and sows again in the old
basins. Stubble clumps laid between basins are in turn used as a food
source by termites.

Planting pits achieve fast rehabilitation of severely degraded land,
especially in a semi-arid climate where a short fallow period of natural
grass growth (2-6 years after 2-3 years under crops) cannot be expected
to maintain or restore the land’s agricultural productivity (FAO, 1994).

http://www.fao.org/docrep/009/a0100e/a0100e07.htm#bm07.6.2