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Zai is an indigenous rainwater harvesting method from Chad

Submitted by Nitya Jacob 18th November 2022 6:01
Zai pits

A farmer prepares pits for Zai

Introduction

Farmers in Chad’s semi-arid Sahelian zone have been using an indigenous rainwater harvesting technique called Zaï to successfully grow crops. Zaï involves the digging of small pits and sowing crops in them. The pits retain water for a long period of time and are particularly efficient when there isn’t much rain. The Zaï technique was enhanced by introducing manure and compost into the pits to provide nutrients to the crops. This helped rehabilitate soils that are heavily degraded and significantly increased the yields of food crops.

This technique can help Chad, assessed as the most vulnerable country to climate change, in food security. Around 87% of Chadians are classified as poor, according to the Multidimentional Poverty Index, which factors in health, education and living standards. That’s the fourth highest rate in the world. The percentage who are “destitute” (63%), the most extreme category of poverty, is also the fourth highest in the world.This is exacerbated by the fact that the country has been in civil war or conflict for 35 out of the 57 years since it gained independence from France.

Any poor or conflict-prone country will always be vulnerable, but Chad’s geography means climate change is a particular risk. Chad is a large country, at 1.28million sq km. About 90% of its 10m people live in the southern half of the country, as most of the northern half extends well into the Sahara desert.

Zai and subsistence farming

As many as 80% Chadians base their livelihoods on subsistence farming and livestock rearing. The semi-arid range lands of the Sahel, in the north of the country, provide pasture for livestock during the rainy season, while the fertile agricultural fields in the south produce most of the cash and food crops. When the dry season begins, pastoralists move their herds south to feed on the leftovers of the agricultural harvest.

Since the mid-20th century, temperatures in Chad have been increasing while rainfall is decreasing and 90% of the country’s largest lake, Lake Chad, has disappeared over the past 50 years due to a combination of droughts and increasing withdrawals for irrigation. Climate studies project things will get increasingly hot and arid throughout the 21st century, which means lower crop yields, worse pasture, and a harder life for anyone dependent on Lake Chad. Rural areas are most at risk from climate change because that’s where most of the population, and most of the poverty, is found. Northern Chad is so dry that they only get about 7 inches of rain per year. They receive all of this rainfall in 3 - 4 months, June to September. Central Chad receives about 21.9 inches of rain on average per year. Finally, Southern Chad receives about 42.7 inches of rainfall per year. Despite these challenges, there are ways to mitigate the effect of climate change.

The technique

For instance, farmers in Chad’s semi-arid Sahelian zone have been using an indigenous rainwater harvesting technique called Zaï to successfully grow crops. Zaï involves the digging of small pits and sowing crops in them. The pits retain water for a long period of time and are particularly efficient when there isn’t much rain. The Zaï technique was enhanced by introducing manure and compost into the pits to provide nutrients to the crops. This helped rehabilitate soils that are heavily degraded and significantly increased the yields of food crops. Agroforestry, the combining of crops and trees in the same patch of land, can also help mitigate and adapt to the impacts climate change. Tree roots stabilise soils and protect them from eroding during heavy rainfall, while also restoring fertility simply by producing litter which eventually makes its way back into the earth.

Zai, or “Tassa,” is a method of farming where each plant has its own hole about 15 - 60 cm wide and 10 - 30 cm deep. These pits focus the minimal rain that falls, straight to the roots of the plant. The base of the stem would begin at the bottom of the pit below ground level instead of at ground level. With each plant having basically a funnel directing any rain to the roots. This improvement can raise yields anywhere from 100 percent to 500 percent! This system is excellent at being efficient even when there is not much rain. When it rains, the water runs to the base of the plant and most importantly it stays there longer than traditional farming methods. It remains there longer because of organic materials that is put into the pits for this purpose. In sum, digging these holes makes the rainwater funnel into the plant's roots and it keeps it there.

The impact

Zai farming turns the previously unusable ground into very effective farmland. This works when the ground is not permeable or just dry. Zai farming originated in Ghana and West Africa. They discovered that this practice is very labor intensive but can improve yields anywhere from 100 to 500 percent! Another benefit of Zai is that it offers farmers a proper way to use manure and other compost. One Zai pit can use about 300 grams of compost a year. Zai farming meets the three categories of conservation set by the United Nations Environment Program; soil conservation, water conservation, and erosion protection. The UNEP also says that Chad is very suitable for Zai farming. Other attempts, such as agroforestry to prevent erosion and desertification, efforts are beneficial, but not nearly as Zai farming could be. Increasing each plant's yield by at least 100 percent would produce much more crops and effectively save many lives.

Challenges

There are few disadvantages to Zai however. Zai pits need constant work and care. Each dry season, a farmer has to dig out excess soil in the holes with a pickaxe and/or a shovel and then fill in more compost before the wet season comes.

Another disadvantage is that if it rains too much in an area. The plants in the pits are vulnerable to becoming waterlogged and dying. Flooding would not be concern for many people in Chad as they barely measure an inch of rain every year.

Desertification is a huge problem in Chad because the amount of arable land is reducing. Zai farming has been proven to stop desertification in nearby countries such as Burkina Faso and Ghana. The process of zai farming is simple and requires minimal capital to start. First, a farmer would dig a pit 15 - 60 cm wide and 15 - 60 cm deep. Next, the farmer would fill the bottom of the pit halfway with organic materials such as dry leaves or corn stalks to help keep in the water. These materials will eventually decompose which helps improve the quality of the soil. Then, top soil and manure are mixed and placed in the pit. In all, the purpose of these pits is to raise yields. How does this happen? The pits harvest rainwater more efficiently than traditional practices. The organic matter will also slow the water and keep the soil moist much longer and more effectively than just pure dirt. This combats the droughts which are very common in Chad.

Another benefit is that all of the nutrients that are in the soil are utilized and focused. When a farmer plants crops, they can now focus exactly where to put the fertilizer/manure and it will stay there. There is no runoff or drifting because it will stay in the sunken pit. Another benefit is that there is less competition from weeds because the most fertile of the soil is only where you are trying to grow your crops. And if weeds do grow, if would be much easier to pull them out when they are focused in the pits. There is the obvious benefit of vastly increased yields. When yields increase 500 percent there is much more food produced to help feed the community. There are also proven food crops that can be grown in Chad. One potential crop to feed people is sorghum. Sorghum can produce human food, feed for livestock, molasses, and pasturage. This crop is already grown in Chad and Zai farming can improve yields and make this already important crop very productive.

Corn and maize produce quite a bit of edible food that is able to grow where there is a little more rainfall. Sweet potatoes and other tubers can be grown to produce food for the people that need the food. Some legumes are also well suited for the harsh environment of Chad.