Exploring effects of weed management in agroecosystems: subterranean arthropods, soil properties and soybean production

Variations in weed management can impact multiple aspects of agroecosystems including the soil arthropod community. Many subterranean arthropods contribute to overall soil and plant health, but it’s unclear how specific taxa, especially Collembola, respond to common weed management practices. In 2012, a field experiment was conducted in North Dakota with three weed management treatments (glyphosate, hand-weeded and weedy) and two insecticide treatments (with and without soil insecticide) in two soybean fields that differed in soil texture. The weed management treatments were specifically designed to separate the effect of the chemical from the presence or absence of the weeds. The soil insecticide was used to lower soil arthropod densities to determine their impact in the system. Objectives were to elucidate (1) effects of weed management practices on Collembola densities and (2) interactions between soil arthropods and weed management on soil properties and soybean parameters. Collembolan densities were significantly higher (P<0.05) in weedy plots than glyphosate plots.  Plots with insecticide had lower densities of soil arthropods as well as lower levels of soil nitrate. However, soybean root biomass and number of nodules were unaffected by the insecticide treatment, although they were highest in glyphosate plots and lowest in weedy plots. Collembola and other soil arthropod taxa can be beneficial in agroecosystems but the weedy plots they were more abundant in had reduced soybean growth. Ultimately, this research can used to help producers create weed management strategies that maximize benefits associated with soil arthropods while minimizing detrimental impacts of weed populations.