EFFECTS OF HERBICIDES ON SOILMICROARTHROPODS RICHNESS AND DISTRIBUTION IN TROPICAL SOILS IN NIGERIA

This study investigated the effects of herbicides on soil microarthropods richness and distribution conducted from August to December 2017 in tropical soils in Nigeria. A split-plot design with six replicates arranged in a Randomized Complete Block Design was adopted. The doses for glyphosate were treated to the plots as low (1.4ml/m2 active ingredient), standard (2.8ml/m2 a.i) and high (5.6ml/m2 a.i), and for multrazine, as low (2.1ml/m2 a.i), standard (4.2ml/m2 a.i) and high (8.4ml/m2 a.i) with a control included. Moist soil samples were randomly collected from treated and control plots with an 8.5 cm2 diameter bucket-type auger at the depths of 0-5cm, 5-10cm, 10-15cm, and 15-20cm between the hours of 8 to10am. A total of 14 soil microarthropods comprising Cryptostigmata (8), Mesostigmata(3)and Collembola(3) were recorded. Oribatid mites- Scheloribates sp., Galumna sp., and Bicrythermannia sp. were the dominant groups recorded at each sampling period. The highest number of soil microarthropods was recorded from the control plots. The study revealed that both glyphosate and multrazine herbicides have effect on the richness and distribution of soil microarthropods, though the effect of multrazine was highly severe. Therefore, Galumna, S. yorubanensis and B. nigeriana tolerated the herbicides and could be used as monitor species. Both herbicides completely eliminated collembola from the treated plots. In all the treatments, fewer soil microarthropods were recorded as soil depth increased. The ecological impact of this study is that glyphosate is environmentally friendlier than multrazine herbicides to agro-ecosystems. Similarly there was a statistical difference between the treatments.