Insect Activity and weather conditions affect CO2 and N2O Emissions from Dung Pats

The feeding and tunneling activities by insects have been shown to alter gas emissions from cattle dung. To determine the magnitude of this effect on semiarid native pastures, we quantified N2O emissions from dung pats with or without insects activities (cloth cover vs. non-cover to the chamber) and with or without ivermectin in dung. Ivermectin is a commonly used parasiticide to treat cattle and was added to the dung to reduce insect activity in a 2X3 factorial design (included CK bare surface without dung treatment). The N2O fluxes were collected over two year study (June 2016-June 2018).
The cumulative annual N2O emissions were affected by dung treatment and insect activities but not by sampling year or their interaction effect. The N2O emission from dung pats with or without ivermectin was 3.5 times values from soil surface without dung pats. Ivermectin had no effect on N2O emissions. Additionally, N2O emission from dung pats without insects was 1.9 times the value of dung pats with insects. However, the emission factor (EF, the amount of N in dung emitted as N2O) was affected the dung treatment, insect activity, experimental year and interactions among them. Emission were highest in year two from invermectin dung without insect activities, followed by same treatment in year one and non-ivermectin dung from both years, they are all higher than EF from dung with insect activity. The feeding and tunneling activities of insects appears to play an important role mitigating N2O emitted from dung pats on semiarid native pastures.