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Impact of the Zaï technique on cowpea production and on the evolution of degraded bare soils chemical characteristics in Burkina Faso. Volume 15, issue 3, JUILLET-AOÛT-SEPTEMBRE 2004

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Unité de formation et de recherche en science de la vie et de la terre, Université de Ouagadougou 03 BP 7021, Ouagadougou 03, Burkina Faso

In the Sudanian zone of Burkina characterised by a low rainfall and a degradation of the soils, producers have resorted to a traditional technique, that of the zaï for soil restoration and water conservation. This technique consists in digging poquets of 20 to 30 cm in diameter and 15 to 20cm deep in order to collect runoff water. Compost or dry dung is generally used as organic fertiliser. The aim of the present article is to show the efficiency of this agricultural practice on cowpea production, a leguminous whose consumption is widespread and which is also a source of substantial income for producers, and to measure its impact on the evolution of the chemical characteristics of the soil. The study was carried out in a field in the province of Passoré, a Northern Sudanian zone characterised by an important development of degraded bare soils. The quantity of the rainfall recorded from June to October 2002, the period covering the cropping season, is 404mm. Four fertilisers were used in order to measure the impact of the amendment: manure, natural phosphate (Burkina phosphate), compost and Loudetia togoensis straw. The test was conducted on a ferruginous tropical soil (Alfisol). This study showed that, through the zaï technique, it is possible to produce cowpea on degraded bare soils. The best yields come from manure and from Burkina phosphate. Compost gave unsatisfactory results and Loudetia togoensis straw proved inefficient during the first season. As regards the soil, the noticeable tendency is the improvement of its chemical characteristics: rise in the pH and in the contents of organic matter as a result of the different amendments, particularly that of phosphorus and calcium following the use of Burkina phosphate. The expected gain of nitrogen through symbiotic fixation of the atmospheric nitrogen by cowpea was not observed during this first season.