Abstract

B. N. Iloba1and T. Ekrakene2*

Soil arthropods recovery rate was monitored for five months (April - August) 2007 to ascertain whether the application of dichlorov (an organophosphate) pesticide, in varying concentration levels of 0 L(control), 0.25 L (low) and 0.75 L (high) per 25 m2 would adversely affect the rate of sampling soil arthropods within a 5 - 10cm depth. Berlese Tullgren Extraction method, sorting and identification of sampled species were adopted and soil physiochemical properties were measured. Insects from eight different groups were consistently sampled. They are members Collembola, Coleoptera, Acarina and Isoptera. Others include Hymenoptera, Myriapoda, Crustaeca and Arachnida. There was an initial decrease in the monthly number of sampled soil arthropods in the treated plots from April to May but increased from June to August. Members of Acarina, Coleoptera and Myriapoda showed the highest fauna abundance while species from Hymenoptera, Crustaeca and Arachnida showed least fauna abundance. Members of Acarina (mites) exhibited the highest recovery rate while Arachnidan species were least. The result revealed that, the mean number of sampled soil arthropods was significantly different (p < 0.05) on the basis of the amount of dichlorov pesticide concentration used compared with the control with high concentration region being the most toxic to the arthropods, hence recording the least number of sampled soil arthropods. On the basis of concentration of applied organophosphate, the soil hydrocarbon content (0.03 - 3.95), soil pH (6.3 - 6.9), soil temperature (25.0 - 29.7°C) and soil moisture (3.2 - 6.9) were not significant (p > 0.05). However, increase in soil moisture from April to August was observed to result in the increase in mean numbers of soil arthropod groups sampled. The implication of this study is that, the depth of 0 - 5 cm mark into the soil litter is not the only arthropod bound zone and soil micro arthropod abundance in the soil is dependent among others on the concentration of pesticide applied. Where application is not indiscriminate, soil micro arthropods have high recovery rate which could enhance high productivity from the soil in the long run.