The effect of soil amendments on the greenhouse gas production in agricultural peat soils

Abstract

Abstract

Soil amendments can improve soil productivity, but they can affect the production and emissions of greenhouse gases (GHG). We studied the effect of gypsum, foundry sand, calcium carbonate and biochar on GHG production rates and microbial community structure in laboratory bottle incubation experiments for peat soils. Four agricultural peatland and two forested peatland soils were selected for the study. Biochar was found to increase nitrous oxide (N2O) production in the majority of the soil samples by an average of 212% in agricultural soils where the increase was statistically significant. Calcium carbonate (CaCO3) had a similar effect, increasing N2O production by an average of 319%, but this change was not detected in as many soils. Calcium carbonate and foundry sand amendments also increased carbon dioxide (CO2) production by an average of 40% and 44%, respectively, in the tested agricultural soils, while biochar and gypsum amendments reduced it by 34% and 28, respectively. Methane (CH4) production in all soils was mainly negative, indicating CH4 uptake, and in agricultural soils, it was mainly unaffected by amendments, except CaCO3, which reduced uptake. In the afforested and forest site soils, however, gypsum and CaCO3 amendments significantly reduced CH4 uptake by the soil but did not turn the soils into net sources of CH4. Nitrous oxide production increased with decreasing pH in agricultural soils. The microbial community structure was significantly different between agricultural and forest sites due to a higher abundance of Crenarchaeota phylum in the forest soil, which included mainly the ammonia-oxidizing Thaumarchaeota. This, among other differences in the microbial community structure, could explain why the soils reacted differently to the soil amendments. The ordination analysis showed that N2O production was related to low pH, low sulfate concentration, low soil moisture and low water holding capacity. Conclusively, our results show that the physical and chemical properties of the soil, as well as the structure of the soil microbial community, can determine the way CO2, CH4 and N2O production in agricultural peatland soil changes in response to different soil amendment uses.