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Nitrification Is a Primary Driver of Nitrous Oxide Production in Laboratory Microcosms from Different Land-Use Soils

View Article: PubMed Central - PubMed

ABSTRACT

Most studies on soil N2O emissions have focused either on the quantifying of agricultural N2O fluxes or on the effect of environmental factors on N2O emissions. However, very limited information is available on how land-use will affect N2O production, and nitrifiers involved in N2O emissions in agricultural soil ecosystems. Therefore, this study aimed at evaluating the relative importance of nitrification and denitrification to N2O emissions from different land-use soils and identifying the potential underlying microbial mechanisms. A 15N-tracing experiment was conducted under controlled laboratory conditions on four agricultural soils collected from different land-use. We measured N2O fluxes, nitrate (NO3-), and ammonium (NH4+) concentration and 15N2O, 15NO3-, and 15NH4+ enrichment during the incubation. Quantitative PCR was used to quantify ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Our results showed that nitrification was the main contributor to N2O production in soils from sugarcane, dairy pasture and cereal cropping systems, while denitrification played a major role in N2O production in the vegetable soil under the experimental conditions. Nitrification contributed to 96.7% of the N2O emissions in sugarcane soil followed by 71.3% in the cereal cropping soil and 70.9% in the dairy pasture soil, while only around 20.0% of N2O was produced from nitrification in vegetable soil. The proportion of nitrified nitrogen as N2O (PN2O-value) varied across different soils, with the highest PN2O-value (0.26‰) found in the cereal cropping soil, which was around 10 times higher than that in other three systems. AOA were the abundant ammonia oxidizers, and were significantly correlated to N2O emitted from nitrification in the sugarcane soil, while AOB were significantly correlated with N2O emitted from nitrification in the cereal cropping soil. Our findings suggested that soil type and land-use might have strongly affected the relative contribution of nitrification and denitrification to N2O production from agricultural soils.

No MeSH data available.


Changes in AOA and AOB amoA gene copy numbers in the 15NH4 treatment during the incubation period. Error bars represent standard error.
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Figure 3: Changes in AOA and AOB amoA gene copy numbers in the 15NH4 treatment during the incubation period. Error bars represent standard error.

Mentions: The abundance of AOB amoA genes was always lower than that of AOA amoA genes in all four agricultural soils (Figure 3). The highest AOA amoA gene abundance was found in the vegetable soil at day 0 (1.5 × 107 copies g−1 dry soil), while the highest AOB amoA abundance was observed in the cereal cropping soil at day 0 (9.1 × 105 copies g−1 dry soil). Following application of fertilizers, both AOA and AOB amoA gene abundance significantly increased in the four soils (p < 0.05). The cereal cropping soil had the largest AOB population throughout the incubation period (on average 2.9 × 107 copies g−1 dry soil), whilst AOA amoA gene abundance in the sugarcane soil (on average 2.5 × 108 copies g−1 dry soil) were found to be higher than those in the vegetable soil (on average 8.6 × 107 copies g−1 dry soil), the cereal cropping soil (on average 1.0 × 108 copies g−1 dry soil) and the dairy pasture soil (on average 1.7 × 108 copies g−1 dry soil; Figure 3). In the sugarcane soil the ratio of AOA to AOB was the highest and averaged at 61.4, followed by the dairy pasture soil averaged at 24.5, vegetable soil at 23.2 and cereal cropping soil at 5.4 within the whole incubation period. Although AOA were more abundant than AOB, the magnitude of changes in AOB abundance in the microcosm was greater than that of AOA.


Nitrification Is a Primary Driver of Nitrous Oxide Production in Laboratory Microcosms from Different Land-Use Soils
Changes in AOA and AOB amoA gene copy numbers in the 15NH4 treatment during the incubation period. Error bars represent standard error.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016788&req=5

Figure 3: Changes in AOA and AOB amoA gene copy numbers in the 15NH4 treatment during the incubation period. Error bars represent standard error.
Mentions: The abundance of AOB amoA genes was always lower than that of AOA amoA genes in all four agricultural soils (Figure 3). The highest AOA amoA gene abundance was found in the vegetable soil at day 0 (1.5 × 107 copies g−1 dry soil), while the highest AOB amoA abundance was observed in the cereal cropping soil at day 0 (9.1 × 105 copies g−1 dry soil). Following application of fertilizers, both AOA and AOB amoA gene abundance significantly increased in the four soils (p < 0.05). The cereal cropping soil had the largest AOB population throughout the incubation period (on average 2.9 × 107 copies g−1 dry soil), whilst AOA amoA gene abundance in the sugarcane soil (on average 2.5 × 108 copies g−1 dry soil) were found to be higher than those in the vegetable soil (on average 8.6 × 107 copies g−1 dry soil), the cereal cropping soil (on average 1.0 × 108 copies g−1 dry soil) and the dairy pasture soil (on average 1.7 × 108 copies g−1 dry soil; Figure 3). In the sugarcane soil the ratio of AOA to AOB was the highest and averaged at 61.4, followed by the dairy pasture soil averaged at 24.5, vegetable soil at 23.2 and cereal cropping soil at 5.4 within the whole incubation period. Although AOA were more abundant than AOB, the magnitude of changes in AOB abundance in the microcosm was greater than that of AOA.

View Article: PubMed Central - PubMed

ABSTRACT

Most studies on soil N2O emissions have focused either on the quantifying of agricultural N2O fluxes or on the effect of environmental factors on N2O emissions. However, very limited information is available on how land-use will affect N2O production, and nitrifiers involved in N2O emissions in agricultural soil ecosystems. Therefore, this study aimed at evaluating the relative importance of nitrification and denitrification to N2O emissions from different land-use soils and identifying the potential underlying microbial mechanisms. A 15N-tracing experiment was conducted under controlled laboratory conditions on four agricultural soils collected from different land-use. We measured N2O fluxes, nitrate (NO3-), and ammonium (NH4+) concentration and 15N2O, 15NO3-, and 15NH4+ enrichment during the incubation. Quantitative PCR was used to quantify ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Our results showed that nitrification was the main contributor to N2O production in soils from sugarcane, dairy pasture and cereal cropping systems, while denitrification played a major role in N2O production in the vegetable soil under the experimental conditions. Nitrification contributed to 96.7% of the N2O emissions in sugarcane soil followed by 71.3% in the cereal cropping soil and 70.9% in the dairy pasture soil, while only around 20.0% of N2O was produced from nitrification in vegetable soil. The proportion of nitrified nitrogen as N2O (PN2O-value) varied across different soils, with the highest PN2O-value (0.26&permil;) found in the cereal cropping soil, which was around 10 times higher than that in other three systems. AOA were the abundant ammonia oxidizers, and were significantly correlated to N2O emitted from nitrification in the sugarcane soil, while AOB were significantly correlated with N2O emitted from nitrification in the cereal cropping soil. Our findings suggested that soil type and land-use might have strongly affected the relative contribution of nitrification and denitrification to N2O production from agricultural soils.

No MeSH data available.