Diffusion Chamber for Nitrogen‐15 Determination of Coupled Nitrification‐Denitrification around Soil‐Manure Interfaces

Abstract

Denitrifying activity in soil is often associated with anoxic microsites rich in organic material, but previously described procedures for determining denitrification rates are not satisfactory when high rates of both nitrification and denitrification are associated with such hot spots. Coupled nitrification‐denitrification associated with hot spots of cattle manure was analyzed by use of a recently developed isotope pairing method in combination with a newly designed diffusion chamber. The diffusion chamber contained three separate phases: an anaerobic manure layer on top, an aerobic soil layer below that placed on top of a highly permeable aluminum oxide filter, and below the filter sterile water containing 15NO−3. The soil could be kept at a water potential below field capacity by suction of a hanging water column connected to the water phase. The isotopically labeled NO−3 entered the soil through the filter and diffused through the soil to the manure where it was denitrified. While diffusing through the soil, 15NO−3 was mixed with 14NO−3 formed by nitrification. The isotopic composition of the N2 formed by denitrification of the mixed NO−3 could then be used to determine the rate of denitrification based on 15NO−3 from the water as well as the rate of coupled nitrification‐denitrification within the soil. The rate of coupled nitrification‐denitrification increased exponentially during the first days after application of manure, indicating exponential growth of the nitrifiers with a doubling time of 1.7 d. The rate reached a maximum of 116 nmol N2 cm−2 h−1 after 10 d and subsequently decreased to 20 nmol N2 cm−2 h−1 after 3 wk. After 3 wk, about 40% of the NH+4 initially present had been removed through coupled nitrification‐denitrification.

Structure and function of a nitrifying biofilm as determined by in situ hybridization and the use of microelectrodes

“…The nitrifying activity of approximately 0.8 mol ⅐ cm Ϫ2 ⅐ h Ϫ1 found in this study is very high compared with previous microsensor studies of nitrifying sediments (24) but is comparable to rates found at the surface of manure clumps in soil (37). The nitrifying layer in the investigated biofilm was only approximately 25 m thick, indicating extremely high specific rates of approximately 30 mol ⅐ cm Ϫ3 ⅐ h Ϫ1 .…”

Structure and function of a nitrifying biofilm as determined by in situ hybridization and the use of microelectrodes

“…The nitrifying activity of approximately 0.8 mol ⅐ cm Ϫ2 ⅐ h Ϫ1 found in this study is very high compared with previous microsensor studies of nitrifying sediments (24) but is comparable to rates found at the surface of manure clumps in soil (37). The nitrifying layer in the investigated biofilm was only approximately 25 m thick, indicating extremely high specific rates of approximately 30 mol ⅐ cm Ϫ3 ⅐ h Ϫ1 .…”

Transient N 2 O accumulation and emission caused by O 2 depletion in soil after liquid manure injection

“…An initially large concentration of NO 3 − (1.34 µmol l −1 ) in the soil served as an electron acceptor for denitrification during the first days after manure application. Transformation of the existing NO 3 − pool to N 2 O or N 2 following addition of easily degradable organics such as manure to the soil has also been demonstrated by others (Comfort et al , 1990; Nielsen & Revsbech, 1994; Clemens & Huschka, 2001). As the inner part of the core was completely anoxic and NO 3 − , electron donors and denitrifiers are expected to have been equally distributed in the core (the soil was mixed before repacking into the boxes and the manure was evenly distributed in the soil‐manure core), it is fairly reasonable to assume a uniformly distributed production of N 2 O and N 2 within the anoxic core.…”

Short-Term Nitrous Oxide Emissions from Cattle Slurry for Silage Maize: Effects of Placement and the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP)

“…A larger surface area would promote the exchange of O 2 , NH 4 + and NO 3 − between manure and soil. This in turn would stimulate the decomposition of labile C and N transformations [35] and support the growth of microbial populations, including nitrifiers and denitrifiers, around manure-soil interfaces [36]. The faster onset of NO 3 − -N accumulation with untreated non-placed slurry (Figure 3) could thus be due to a higher NH 4 + availability for nitrifiers, and more coupled nitrification-denitrification during May enhancing N 2 O emissions compared to placed slurry (Figure 7).…”

Structure and function of a nitrifying biofilm as determined by in situ hybridization and the use of microelectrodes

“…The nitrifying activity of approximately 0.8 mol ⅐ cm Ϫ2 ⅐ h Ϫ1 found in this study is very high compared with previous microsensor studies of nitrifying sediments (24) but is comparable to rates found at the surface of manure clumps in soil (37). The nitrifying layer in the investigated biofilm was only approximately 25 m thick, indicating extremely high specific rates of approximately 30 mol ⅐ cm Ϫ3 ⅐ h Ϫ1 .…”

Transient N 2 O accumulation and emission caused by O 2 depletion in soil after liquid manure injection

“…An initially large concentration of NO 3 − (1.34 µmol l −1 ) in the soil served as an electron acceptor for denitrification during the first days after manure application. Transformation of the existing NO 3 − pool to N 2 O or N 2 following addition of easily degradable organics such as manure to the soil has also been demonstrated by others (Comfort et al , 1990; Nielsen & Revsbech, 1994; Clemens & Huschka, 2001). As the inner part of the core was completely anoxic and NO 3 − , electron donors and denitrifiers are expected to have been equally distributed in the core (the soil was mixed before repacking into the boxes and the manure was evenly distributed in the soil‐manure core), it is fairly reasonable to assume a uniformly distributed production of N 2 O and N 2 within the anoxic core.…”

Short-Term Nitrous Oxide Emissions from Cattle Slurry for Silage Maize: Effects of Placement and the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP)

“…A larger surface area would promote the exchange of O 2 , NH 4 + and NO 3 − between manure and soil. This in turn would stimulate the decomposition of labile C and N transformations [35] and support the growth of microbial populations, including nitrifiers and denitrifiers, around manure-soil interfaces [36]. The faster onset of NO 3 − -N accumulation with untreated non-placed slurry (Figure 3) could thus be due to a higher NH 4 + availability for nitrifiers, and more coupled nitrification-denitrification during May enhancing N 2 O emissions compared to placed slurry (Figure 7).…”

Structure and function of a nitrifying biofilm as determined by in situ hybridization and the use of microelectrodes

“…The nitrifying activity of approximately 0.8 mol ⅐ cm Ϫ2 ⅐ h Ϫ1 found in this study is very high compared with previous microsensor studies of nitrifying sediments (24) but is comparable to rates found at the surface of manure clumps in soil (37). The nitrifying layer in the investigated biofilm was only approximately 25 m thick, indicating extremely high specific rates of approximately 30 mol ⅐ cm Ϫ3 ⅐ h Ϫ1 .…”

Transient N 2 O accumulation and emission caused by O 2 depletion in soil after liquid manure injection

“…An initially large concentration of NO 3 − (1.34 µmol l −1 ) in the soil served as an electron acceptor for denitrification during the first days after manure application. Transformation of the existing NO 3 − pool to N 2 O or N 2 following addition of easily degradable organics such as manure to the soil has also been demonstrated by others (Comfort et al , 1990; Nielsen & Revsbech, 1994; Clemens & Huschka, 2001). As the inner part of the core was completely anoxic and NO 3 − , electron donors and denitrifiers are expected to have been equally distributed in the core (the soil was mixed before repacking into the boxes and the manure was evenly distributed in the soil‐manure core), it is fairly reasonable to assume a uniformly distributed production of N 2 O and N 2 within the anoxic core.…”

Short-Term Nitrous Oxide Emissions from Cattle Slurry for Silage Maize: Effects of Placement and the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP)

“…A larger surface area would promote the exchange of O 2 , NH 4 + and NO 3 − between manure and soil. This in turn would stimulate the decomposition of labile C and N transformations [35] and support the growth of microbial populations, including nitrifiers and denitrifiers, around manure-soil interfaces [36]. The faster onset of NO 3 − -N accumulation with untreated non-placed slurry (Figure 3) could thus be due to a higher NH 4 + availability for nitrifiers, and more coupled nitrification-denitrification during May enhancing N 2 O emissions compared to placed slurry (Figure 7).…”