To increase soil fertility, it is necessary to increase the recycling of organic matter. One approach is to plant trees that can produce green manure. Research conducted at ICRISAT in Niger showed that Acacia tumida is a species which produces a lot of green manure (see chapter on soil fertility). Acacia tumida can be planted in areas where the rainfall is higher than 300 mm. The Acacia collei has also been tested, but this species is less resistant to drought than the Acacia tumida. After the second year, each Acacia collei tree produces 14 kg of organic matter. A study carried out in demonstrates that the Acacia tumida can grow by 2.4 m in 14 weeks (Houérou 2006).

The advantage of Acacia tumida is that the leaves of this tree are not grazed by animals from the second year after their establishment. The Acacia tumida trees just need to be protected during the first year. 

The Acacia tumida may be planted with a space of 10 metres between the rows and 5 meters within rows (source D.Paternak). This corresponds to 200 trees per hectare. In addition, it is possible to plant the tree as a fence around the field. The Acacia tumida leaves slowly decompose in the soil. Even after 2 years, the leaves do not add much nitrogen to crops. During the initial years, mulching rather reduces erosion and protects plants against wind. Termites contribute to decomposing Acacia leaves. It is possible to plant millet and cowpea near Acacia tumida fences without producing any negative effect on the yield.     

The Acacia tumida must be pruned each year or every second year in order to produce green manure. The pruning time is April, after the pods are harvested. 

Another advantage of the Acacia tumida is that the grains are edible and there is a market in Europe for these grains. The grains are also consumed by the Aboriginal people in Australia. These grains also constitute good food for hens as they have 18% protein content.

In order to establish a hedge of Acacia tumida fence (see photo), seedlings raised in nurseries are used. Direct seeding is too risky. The Acacia tumida fence is an effective windbreak and it has a net effect on the speed of the wind. This contributes to reducing evapo-transpiration.

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