Effects of soil aggregate size, moisture content and fertilizer management on nitrous oxide production in a volcanic ash soil

Abstract

A laboratory incubation study was conducted to determine the effects of soil aggregate size, soil moisture content and manure application on nitrous oxide (N 2 O) production through nitrification and denitrification. In Southern Hokkaido, soil samples were taken from a mineral soil layer (2.5-10 cm) of a grassland to which chemical fertilizer and manure had been applied. The soil aggregates were air-dried and sieved with 4.5 mm and 2 mm sieves, and the soil moisture was adjusted to 60% and 80% of field water capacity (FWC). Immediately after moistening, incubation was initiated and lasted for 9 days at 20 C. Following the start of incubation, a flush of N 2 O, carbon dioxide (CO 2 ) and nitric oxide (NO) was observed. Production of all gases was higher in larger aggregates from the manure-applied soil. Productions of CO 2 and NO were not significantly influenced by soil moisture content, but N 2 O production was considerably higher in 80% FWC as compared with 60% FWC. Based on the results of the N 2 O-nitrogen (N)/NO-N ratio, the process of N 2 O production was mainly due to nitrification in 60% FWC and denitrification in 80% FWC. Soil chemical properties, especially ammonium-N ðNH þ 4 -N), nitrate-N (NO 3 -N) and water extractable organic C (WEOC) and microbial biomass C (MBC) also changed immediately after moistening. These changes were higher in larger aggregates from the manure-applied soil. Potential denitrification enzyme activity (DEA) was significantly higher in larger aggregates from manure-applied soil with higher moisture content. The N 2 O production in both 60% and 80% FWC correlated significantly with MBC and DEA. Regardless of soil moisture conditions, MBC correlated significantly with DEA, WEOC consumption and apparent N mineralization. These facts suggest that larger soil aggregates could have quickly developed suitable internal conditions for microbial activity inside the aggregates and consequently stimulated N 2 O production through nitrification and denitrification.

Nitrogen addition impacts on the emissions of greenhouse gases depending on the forest type: a case study in Changbai Mountain, Northeast China

“…The separated aggregates were oven-dried at 60°C and then weighed. The field water capacity (FWC) was measured using a funnel according to the methods of Diba et al (2011), and the values of the FWC from the largest aggregates to the smallest aggregates were 1.01, 1.03, 1.18, 1.59, and 1.99 g g −1 , respectively.…”

“…The gas production rate (F, mg kg −1 h −1 or μg kg −1 h −1 ) was calculated according to the methods of Diba et al (2011) using the following equation (Eq. (2)):…”

“…However, Plaza-Bonilla et al (2014) observed that inorganic N fertilization promotes the emission of CO 2 and N 2 O in an incubation experiment using agricultural soil. Diba et al (2011) detected that the impact of N addition on N 2 O emission depended on soil aggregate size in grassland soil. Tao and Song (2013) reported that N addition had a neutral and negative effect on SOC decomposition in wetland soil.…”

“…Although recent studies intensively focus on the effect of N deposition on the GHG emissions in field experiments, little is known regarding the effect of the interaction between N addition and soil structure on GHG emissions. Further, Diba et al (2011) have reported that N 2 O emissions could be significantly influenced by soil aggregate size and N addition due to differences in soil properties in various aggregate sizes.…”

Evaluation of greenhouse gas emissions in aMiscanthus sinensisAndersson-dominated semi-natural grassland in Kumamoto, Japan

“…However, these conditions were not optimal for N 2 O consumption. As highlighted by previous studies (Kusa et al 2010;Diba et al 2011), localized spots may exist in soil that are suitable for soil N 2 O consumption with lower oxygen concentration in soil aggregates. With higher soil temperatures and wet conditions in summer, such localized anaerobic spots may be created due to active soil organic matter decomposition and nitrification.…”