In West Africa, the uncontrolled use of pesticides by vegetable farmers leads to contamination of soils as well as surface and ground water. Farmers also use various sources of organic amendments which could impact the fate of the pesticides in soils. This study was conducted to identify the type of pesticides and organic amendments used in the main vegetable gardens in Ouagadougou, Ouahigouya and Bobo-Dioulasso three cities of Burkina Faso. Farmers were interviewed individually on their practices regarding organic amendments and pesticides. Sixty one percent (61%) of farmers do not know the instruction regarding the application of pesticides. Fifty three percent (53%) of farmers did never receive training on pesticide application. We found that pyrethroid-based insecticides like lambda-cyhalothrin and delthametrin were the most used by farmers. About 69%, 59% and 100% of the farmers apply the pesticides periodically in their fields respectively in Ouagadougou, Ouahigouya and Bobo-Dioulasso. All the farmers interviewed attested that they do not respect the recommended doses of pesticides. Manure was the organic amendment mostly used in the three cities (41-75%), followed by household garbage (15-41%). In Ouagadougou most of farmers (69%) apply organic amendment at the recommended rate or more while in Bobo-Dioulasso (69%) and in Ouahigouya (57%), the majority apply low rates. There is a correlation between the social status (sex and the education level) and the pesticide and organic amendment management.

Insects attack vegetable crop, leading to an overuse of pesticides. Organic amendments are recommended to increase soil fertility. The impact of two insecticides, on soil macrofauna under rainfed cultivation of tomato (Lycopersicon esculentum L.) with or without organic amendments was evaluated.The insecticides were Lambda Super (lambda-cyhalothrin) and Dursban (chlorpyrifos ethyl) and organic amendments were compost, pig manure and cattle manure. An experimental device in split-plot with three replicate was installed. Pesticides were applied periodically each week during the experiment. The results have showed that with organic amendments, Lambda super increased the earthworm population compared to the control. Indeed, we found 42 individuals/m 2 with compost; 1 individuals/m 2 with pig manure and 27 individuals/m 2 with cattle manure but the control was 0 individuals/m 2 in the presence of Lambda super without organic amendment. Similarly, Dursban increased the population of earthworms in the presence of organic amendment with 11, 37 and 91 individuals/m 2 respectively for compost, pig manure and cattle manure. Lambda super with compost has led to a total elimination of termites. In the presence of Dursban, a decrease in the number of termites was observed when adding cattle manure (11 individuals/ m 2 ) compared to the control containing only Dursban (21 individuals/m 2 ). Better distribution of macrofauna was obtained with treatment with Dursban and compost (E = 0.99 for earthworms and E = 0.96 for termites). All organic amendments used in our study stimulated earthworm population, but more in the presence of Lambda super or Dursban.

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