We have just prepared the field for one of our 7 research projects this season: Zai.
Zai is a micro-catchment system that originates in Burkina Faso–a country in West Africa. It is a series of holes and mounds. Why would any farmer spend long, back-breaking days digging holes instead of planting straight into the ground?
The first reason is to break surface crusts. In Burkina Faso–at the transition of the semi-arid Sahel and the Sahara desert–it is so dry that even pure sand can bind together so that it is near impossible to direct seed without having to break up the surface in some way. Paradoxically, the more the surface is broken up (with ripping and discing) the more moisture can be lost. Digging Zai disturbs the soil enough so that seeding is possible.
The second reason one might use Zai is to direct all available water into the soil and toward the plant. When rains come infrequently, but in huge downpours, that water must be utilized efficiently. The mounds direct water down into the holes in front and behind it, while the whole field captures surface runoff. This concentrates it to the plant’s roots, and also increases soil infiltration.
Less a reason than a standard practice when using Zai, all amendments are placed into the hole. This concentrates what little nutrients–manures, fertilizers, composts–a farmer has access to right at the plant roots so that it can utilize more of them, compared to banding or, God forbid, broadcasting them.
This practice is transforming Bukina Faso and Mali. Once abandoned land has been reclaimed for agriculture. Zai have also been used to regenerate forests in the desert. Planting trees into the pits helps saplings have better access water (just keep the goats away for a few years). This has in some places halted desertification, and even been used to reverse it, with much hard work and fidelity.
The advance of the desert is every pastoralists’ and farmers’ daily battle along the Sahel. For it to be used continuously for generations, it must be treated with the utmost care (Not unlike the precarious agriculture of ancient Israel. It flowed with milk and honey on the condition of their hard work and vigilance). As rains become more erratic, and droughts lengthen and increase, people are pushed to use increasingly scarce resources more often. The land’s fragile balance of grasses and shrubs are vulnerable to over-grazing and over harvesting. If completely removed, the fragile soil surface is swept away by rain and wind. Once the plants and top-soil are gone, it takes an arduous miracle, like Zai, to begin to bring the land back to life.
These pictures show our method to prepare the field. To make a symmetrical field, a rope or wire can be stretched out and marked exactly where each hole should go. This being our third season with these same Zai holes, we decided to redig them without using a line. Everyone digs a section along the rope, always mounding the dirt in the same direction, in our case, toward the north.
If this experiment were in Burkina Faso, we wouldn’t need to redig the holes. Here is South Africa, there is not a surface crust, so when it rains, the holes fill in. In order to give uniformity to the field and apply the manure at the same depth, we needed to redig–as deep as the hoe blades. Next, we applied the manure, plots having one of two rates (I’ll write next on how the Zai experiment is designed and what it’s looking at). Lastly, we went through the field and mixed the manure into the soil. The field is now ready for planting in late September.
