Soil Macrofauna Behaviour in the Presence of Pesticides and Organic Amendments

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/m2 with compost; 1 individuals/m2 with pig manure and 27 individuals/m2 with cattle manure but the control was 0 individuals/m2 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/m2 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/ m2) compared to the control containing only Dursban (21 individuals/m2). 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.