2018 Alberta Soil Science Workshop program

Ivermectin (IVM) is a parasiticide commonly applied to cattle. Treated cattle excrete faecal residues that can reduce insect activity in cattle dung. The feeding and tunneling activities of these insects alters the chemical and physical properties of both cattle dung and the soil that it covers, potentially affecting available nitrogen (AN) within the soil environment. To determine these effects on semiarid pastures, we deposited cattle dung with and without IVM on soil of a semiarid pasture on 01 June 2016 and on 26 May 2017. We then collected samples representing 5 treatments for which we quantified dung or soil AN; i.e., soil on which dung was not deposited, dung with and without IVM, and soil from beneath each type of dung. Samples were collected at weekly or monthly intervals for one year after time of dung deposition. Results from 2016 indicate lower soil AN beneath dung pats with versus without IVM. Data analyses for 2017 are not yet complete. This study is part of a larger project that combines entomologic, microbial, and greenhouse gas emission monitoring to assess the non-target effects to ecosystem function of IVM residues in cattle dung deposited on pastures.