Effects of Three Pesticides (Atrazine, Deltamethrin and Acetamiprid + Cypermethrin), Two Plant Species (Vetiveria nigritana Benth. and Oxythenantera abyssinica Linn.) and Their Interactions on the Biological Activity of Lixisols and Vertisols of Cotton Agrosystems of Burkina Faso (West Africa)

Aims: The application of pesticides can have adverse effects on the biology of agricultural soils. This study had 3 objectives: (i) evaluate the impact of the three pesticides on soils, (ii) evaluate the impact of the two plant species on soils and (iii) also evaluate the interaction of pesticides and plant species on soils.

Methodology: In order to achieve this aim, an experimental test was conducted in a vegetal vase with 7 treatments. The experimental device used is a split-plot device with four repetitions for each soil type. The main treatments are plant species and secondary treatments consist of pesticides. The main factor had three modalities namely: absence of plant, Oxytenanthera abyssinica and Vetiveria nigritana. As for the secondary factor, it comprises four modalities which are: control, Atrazine, Deltamethrin and Acetamiprid + Cypermethrin. Deltamethrin and acetamiprid + cypermethrin are not a mixture. They constitute 2 different pesticides. It is rather acetamiprid + cypermethrin which is a mixture of acetamiprid and cypermethrin.

Results: Physicochemical characteristics are generally lower in lixisols compared to vertisols, except P and K. Microbial biomass is lower in the presence of plant species regardless of soil type. Microbial biomass has declined regardless of the type of pesticide. This decrease was significant (P = 0.045) in lixisols. Pesticide interaction and plant species significantly increased (P = 0.01) microbial biomass in the presence of Vetiveria nigritana and respiratory activeness for both species. The highest cumulative release values ​​are found in soils without plants. Analysis of variance revealed highly significant differences (P <0.001) in lixisols. The application of Atrazine and Cypermethrin + Acetamiprid increased respiratory activity regardless of soil type. Cumulative values ​​are higher in lixisols than in vertisols.

Conclusion: The pesticides used induce a decrease in the microbial biomass of the soil and promote a stimulation of the respiratory activity. The plant species tested induce a decrease in microbial biomass as well as the mineralization that expresses the release of CO2 in lixisols and vertisols. The interaction between plant species and pesticides increases microbial biomass and respiratory activity in both soil types