Effet des pesticides sur l'activité microbienne d'un sol ferrugineux tropical du Burkina Faso.

L’effet des pesticides utilises en culture cotonniere sur l’activite microbienne globale des sols a ete etudie sur un sol ferrugineux tropical en zone ouest du Burkina Faso. Des echantillons de sol ont ete preleves a 30, 73, et 119 jours apres semis du cotonnier. Les analyses de respirometrie, de determination de la biomasse microbienne et de l’ammonification ont ete realisees. Les resultats indiquent que les doses de pesticides apportees sont insuffisantes pour affecter les bacteries ammonifiantes. En revanche, ces doses perturbent la vie du sol en affectant l’efficience des microorganismes a utiliser la matiere organique, en activant tantot la respiration et la biomasse microbiennes et tantot en les inhibant. Mots Cles : Pesticide – Sol – Activite Respiratoire – Biomasse Microbienne – Bacterie Ammonifiante The effect of pesticides used in cotton cultivation on soil global microbial activity was studied on a tropical ferruginous soil in the west zone of Burkina Faso. The soil samples were took at 30, 73 and 119 days after the cotton seeds. The analyses of respirometry, of microbial biomas  determination and of the ammonification were realized. The results indicate that the doses of pesticides that put aren’t enough to affect ammonificate bacteriums. In return, these doses disrupt soil life by affecting microorganism’s efficiency in using organic matter, by stimulating sometimes microbial’s respiration and biomas, and sometimes inhibiting it. Key words: Pesticide – Soil – Respiratory activity – Microbial biomas – Ammonificate bacterium