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Effects of Tillage as a Disturbance on Soil Microarthropods and Entomopathogenic Nematodes in Oklahoma

Dubie, Trisha Rose
The purpose of this study was to evaluate the effects of agricultural tillage, as a form of soil disturbance, on soil microarthropods and entomopathogenic nematodes (EPN). The field site at Lake Carl Blackwell was set up as a randomized complete block system with 6 blocks, 2 tillage regimes, and 3 repetitions of each treatment. Soil samples (300 cm3) were taken over two seasons on four dates throughout the winter wheat season for microarthropods, and three years on three dates (spring, summer and fall) for EPN. Microarthropods were extracted using Tullgren funnels. EPN were isolated from the soil using waxworm, G. mellonella larvae, bioassays and kept in cultures in the laboratory. Mean abundance six major groups of microarthropods and a seventh group for mean total abundance was analyzed using ANOVA for effects due to tillage and also effects due to season. Six of the seven groups showed higher abundance in no-till soil than conventionally tilled soil on varying dates. In contrast, mites in the group Prostigmata were more abundant in conventionally tilled soil. Infection rates were higher overall in no-till soil. EPN isolates were also preserved for future DNA characterization. Responsible assessments of soil quality in agricultural systems should include evaluations of beneficial soil fauna and important natural enemies such as microarthropods and EPN.