CHAPTER 3 DIRECT MEASUREMENT OF DENITRIFICTION...
Transcript of CHAPTER 3 DIRECT MEASUREMENT OF DENITRIFICTION...
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CHAPTER 3
DIRECT MEASUREMENT OF DENITRIFICTION USING 15N-LABELED
FERTILIZER APPLIED TO TURFGRASS
ABSTRACT
Denitrification losses are a possibility from turfgrass because of frequent
irrigation, multiple applications ofN fertilizers, and an abundance of readily
decomposable organic C in thatch and verdure. Field experiments were conducted to
directly measure N2 and N20 evolved from a Flanagan silt loam soil under Kentucky
bluegrass (Poa pratensis L.) or creeping bentgrass (Agrostis palustris Huds.). Mass
spectrometric procedures were used to analyze atmospheric samples collected from
replicated 15N fertilized turf (49 kg ha-1). Data showed that labeled fertilizer N (LFN)
losses ranged from 2.1 to 7.3% for N2 and from 0.4 to 3.9% for N20; that large N2 and
N20 fluxes occurred after heavy rainfall events; and that more N2 was evolved than N20.
Emission of gas was detected while standing water was visible within cylinders,
suggesting the transfer of gases from the flooded soil to the atmosphere through the
turfgrass plants. Evolution ofN2 and N20 was greater from creeping bentgrass treated
with KN03 than urea through the fIrst 3 wk of the experiment, whereas N2 emission was
greater for urea during the last 2 wk of the experiment, presumably because ofN03
production through nitrification. Nitrous oxide was detected on the day of fertilization
with the KN03 treatment, and the mole fraction ofN20 decreased with each weekly
application ofN from 0.44 to 0.11.
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INTRODUCTION
Denitrification is an important process in the soil, plant, and atmosphere
continuum (SPAC) because it is the primary mechanism for return ofN2 to the
atmosphere (Stevenson and Cole, 1999). With plant productivity frequently limited by N
supply, removal of inorganic N by denitrifying microorganisms can adversely affect plant
growth and development. Moreover, one of the gaseous products of denitrification is
N20, which contributes to the destruction of stratospheric 03 (Prather et aI., 1995).
The potential for extensive denitrification losses from turf cannot be ignored, as
turf represents an unusual "cropping system." With traditional row crops, denitrification
typically occurs in the spring or fall when N03 is present due to recent fertilization and/or
reduced plant uptake, evapotranspiration is minimal, rainfall is high, and readily
decomposable organic C is available as a source of energy (Paul and Clark, 1989). This
combination provides the substrate and anoxic conditions that are necessary for gaseous-
N loss via denitrification. However, soil temperatures during these times are often low
and since the rate of denitrification is temperature dependent (Blackmer et aI., 1982;
Mancino et aI., 1988), gaseous N loss is usually limited (Schnabel and Stout, 1994). In
contrast, highly managed turfgrass represents a system where extensive denitrification
losses could occur from warm soils. These losses would be promoted because irrigation
keeps the soil profile near field capacity and may lead to temporary short-term anoxia
(Sextone et aI., 1985), while multiple applications ofN fertilizer are common, and large
amounts of readily decomposable organic C are present in the thatch and verdure.
Direct measurements to characterize and quantify denitrification losses from
fertilized turfgrass are limited. Because of the inherent difficulties involved in measuring
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the emission ofN2 into ambient air, gaseous N loss by denitrification and/or volatilization
have usually been estimated from the deficits in 15Nbalance studies. Using 15N-Iabeled
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fertilizer, like urea, than with acidic fertilizers. Alkaline-producing fertilizers may
promote denitrification under waterlogged conditions, either because of an increase in the
supply of oxidizable C (Norman et aI., 1987, Sen and Chalk, 1994) or because of a direct
effect on microbial activity (Bollag et aI., 1970). Maggiotto et al. (2000) found that
sulfur coated urea, when compared to urea, suppressed N20 emissions; however, with the
slow-release fertilizer, the suppression ofN20 emission was short-lived.
Plant-based systems are more biologically active as compared to a bare soil, in
that roots are constantly aerating the soil surface, plant senescence supplies
microorganisms with readily available organic C as an energy source, evapotranspiration
is occurring, nutrients are removed from the soil via plant uptake, and, especially for high
maintenance turfgrass, irrigation is typically applied daily. The primary objective of this
research was test the hypothesis that significant gaseous N loss can occur from turfgrass,
by directly measuring fluxes ofN2 and N20. A secondary objective was to evaluate the
effects of fertilizer source on the rate of denitrification.
MATERIALS AND METHODS
Soil
Field studies were conducted in 1999 and 2000 at the University of Illinois
Landscape and Horticulture Research Farm in Urbana, IL. The study site was maintained
under Kentucky bluegrass or creeping bentgrass on a Flanagan soil (fine, smectitic,
mesic, Aquertic, Argiudoll). Analyses of the soil as described by Mulvaney and Kurtz
(1982) gave the following results: pH, 6.8; total N 2.55 g kg-I; organic C, 30.3 g kg-I; a
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sand content of 125 g kg-I, a silt content of 588 g kg-I, and a clay content of287 g kg-I.
All analyses reported were performed in triplicate.
Field Experiments
Two separate experiments were initiated in 1999 by inserting eight PVC cylinders
into Kentucky bluegrass turf to a depth of approximately 25 cm using a tractor-mounted
hydraulic press. A full description of the materials and methods used for constructing
and inserting the modified PVC cylinders is provided in chapter 2. Six PVC cylinders
were selected after verifying that infiltration rates inside and outside the cylinder did not
differ. On 5 May and 9 August 1999 at 0600, KN03 containing 98.5 atom % 15N
(obtained from Isotec, Miamisburg, OR and the enrichment was determined
experimentally) was applied in solution to each plot at a rate of 4.88 g N m-2 (equivalent
to 49 kg N ha-I) using a polyethylene wash bottle. To ensure a complete transfer of the
fertilizer solution, the wash bottle was rinsed three times with a total of 165 mL of water.
Plots were irrigated twice a week to replace 80% of the potential
evapotranspiration (PET) when rainfall totals did not exceed the PET value (obtained
from the Illinois State Water Survey). The turfgrass was maintained at approximately 5
cm using a pair of manual hand clippers to cut the grass while holding a hand-held
vacuum against the clippers. Clippings were collected biweekly. The experimental
design involved atmospheric sampling three times a day (0800 to 1100, 1100 to 1400,
1400 to 1700) with two replications.
An experiment was conducted in the field from 18 July to 21 August 2000 to
compare the effects of different N fertilizers on emission ofN2 and N20 during
denitrification ofN03 from creeping bentgrass turf. Six cylinders were inserted as
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previously described, from which four were selected after verifying that infiltration rates
inside and outside the cylinders id not differ. On 18 July 2000 at 0800, KN03 containing
49.47 atom % 15Nwas applied to two cylinders at a rate of 976.44 mg N m-2 (equivalent
to 9.8 kg N ha-1). Two other cylinders were treated with the same amount ofN as urea
containing 46.8 atom % 15N. Weekly fertilizer applications were made throughout the
experiment as specified previously, and atmospheric sampling occurred daily from 1100
to 1400. Plots were irrigated as needed so as to maintain a healthy turf sward. At
biweekly intervals, the turfgrass was clipped to a height of approximately 1.3 em using
manual hand clippers, and clippings were removed.
Greenhouse Experiment
Six PVC cylinders were inserted into the soil in an area adjacent to the location of
the 1999 experiments, of which three were inserted into bare soil and three into a soil
under Kentucky bluegrass turf. Four of these cylinders were selected (two bare soil and
two turfgrass) after verifying that infiltration rates inside and outside the cylinders did not
differ. The intact cylinders were removed from the soil, and the bottoms were sealed by
inserting modified PVC end caps equipped with a stainless steel male-hose connector
(cat. no. 6-HC-1-4, Swagelok Co., Solon, OH) to permit leachate collection. The sealed
cylinders were transported to the greenhouse, and the plants and soil inside the cylinders
were treated at 0800 on 24 May 2000 with 4.88 g N m-2 (equivalent to 49 kg N ha-1) as
KN03 enriched with 98.5 atom % 15N,which was applied as previously described for the
field studies.
Atmospheric sampling commenced following fertilization and occurred daily
from 1100 to 1400 until 13 June 2000. Irrigation was applied with a polyethylene wash
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bottle at least once a week to maintain adequate turfgrass health. Plants were maintained
under 14-h days (185 mmol sec-1m-2plus ambient sunlight) at 22:i: 2°C and 10-h nights
at 18 :i:2°C for 4 wk. Turfgrass was maintained biweekly at approximately 5 cm using
manual hand clippers and clippings were removed.
Atmospheric Sampling and Gas Analysis
The technique employed for atmospheric sampling is described in detail in
chapter 2. Briefly, a brass lid, equipped with two shut-off valves, was secured to the
plastic flange on the PVC cylinder, thus creating a gas tight seal to collect the gases
evolved from the soil and plants. After 3 h, a closed-loop circulating system was created
by attaching the valves on the lid to a circulating pump and a 60-mL gas sampling tube
equipped with two high vacuum stopcocks, which contained a known amount ofNe.
Both valves and both stopcocks were then opened, and the atmosphere inside the
circulation system was thoroughly mixed by pumping for 20 min. Following pumping,
the stopcocks on the sampling tube were closed, the tube and the pump were
disconnected from the brass lid, and the lid was removed from the PVC cylinder.
Samples were analyzed for 15N-IabeledN2 and N20 as described by Mulvaney
and Kurtz (1982) and for Ne as described in chapter 2 using a dual-inlet ratio mass
spectrometer (Nuclide ModeI3-60-RMS; Spectromedix Corp., State College, PA). Ratio
data were processed using equations derived by Mulvaney and Boast (1986) to obtain
values for the mole fraction of 15Nin the N pool from which the N2 or N20 was derived
(lSXN) and the micrograms ofN as labeled N2 or N20. A value was also obtained for the
percentage ofN2 or N20-N derived from LFN, using the isotope dilution expression, 100
x eSXN
- 0.003663)/(F - 0.003663), where F is the experimentally obtained 15Nfertilizer
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enrichment. The total emission of labeled N2 or N20 was estimated on the assumption
that the N03 undergoing denitrification existed in a single pool that is isotopically
uniform. Emission rates were calculated from the micrograms ofN2 or N20-N
determined by taking into account the atmospheric volume, temperature, and barometric
pressure at the time each plot was sampled, and are expressed as Ilg ofN2 or N20
evolved per m2 of surface soil S.I. For the spring and summer Kentucky bluegrass
experiments, triplicate 3-h emission measurements from within each replication were
summed and means and standard errors were calculated. For all other experiments,
emission measurements were based on a single 3-h enclosure period per replication, from
which means and standard errors were calculated.
RESULTS AND DISCUSSION
Sampling Strategy
If, by inserting the PVC cylinders into the soil, infiltration rates inside the
cylinders differ from the surrounding area, then hydraulic conductivity may have been
reduced by compaction, potentially prolonging anaerobicity and promoting
denitrification. To minimize this potential problem, additional cylinders were inserted
into the soil beyond the number needed for each experiment, so that if infiltration rates
inside the cylinders differed from the surrounding area, these cylinders would not be used
for experimental purposes.
A turfgrass system is inherently complex compared to soil, in that roots are
constantly aerating the soil surface; organic C is readily available as a microbial energy
source due to plant senescence; evapotranspiration dries the soil; nutrients are removed
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from the soil via plant uptake or immobilization and replenished by mineralization; and,
especially for high maintenance turfgrass, irrigation is typically applied daily. Of
concern in our work was internal heating inside the closed cylinders during a 3-h period
of enclosure, as denitrification is a temperature dependant process and elevated
temperatures inside the closed cylinder may lead to larger atmospheric emission rates of
N2 and/or N20. Preliminary work showed no difference during a 3-h period of enclosure
between the air temperature inside and outside the closed cylinder when the brass lids
were painted white to reflect sunlight and shade cloth was tented 0.6 m above the plant
surface. Moreover, no evidence of plant stress was observed following a 3-h enclosure
in any of the experiments conducted.
Another concern was how to measure the atmospheric volume confined within the
closed chamber, because plants preclude the use of a ruler to determine the headspace
volume above the soil surface, whereby volume is used to calculate N2 flux based on the
ideal gas law (pV=nRT). The technique described in chapter 2 was developed to
measure atmospheric volume, including the soil-air volume within a complex plant/soil
matrix. This technique involves a standard addition of an inert gas (Ne) into the closed
chamber prior to circulating the air, so that the atmospheric volume confined within the
chamber can be estimated by measuring the decrease in Ne concentration. The
concentration ofNe in the atmospheric sample collected is proportional to the
atmospheric volume confined with in the closed chamber. This technique allows
determination of atmospheric volume in conjunction with mass spectrometric analyses
for lsN-labeled N2 and N20, and is in effect providing a capability for real-time volume
determinations.
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The Ne technique requires circulation of the air inside the closed cylinder in order
to facilitate diffusion ofNe. There are reports that slight pressures or pressure deficits
generated when air is circulated through chambers placed over the soil surface can have
marked effects on gaseous emission (Denmead, 1979; Hutchinson and Mosier, 1981). If
desired, the chamber lid can be equipped with a low-conductance vent (e.g., 1.4 mm i.d.
tubing) to avoid pressure fluctuations. This was not done in the present project, as
previous work to evaluate a similar sampling system showed that venting did not reduce
short-term variability in emission ofN2 or N20 (Mulvaney and Kurtz, 1984).
Field Experiments
Figures 3 and 4 show the results of daily measurements of LFN and total N
evolved as N2 and N20 from 15N-fertilized Kentucky bluegrass cores during a six-wk
experiment in the spring and a four-wk experiment in the summer. In addition, Fig. 3 and
4 show the amounts of water supplied through irrigation or rainfall and the atmospheric
volume data collected by the Ne technique.
Water inputs and soil texture influence infiltration rates and the soils ability to
drain soil water, thus directly affecting the length of time a soil remains anaerobic. Smith
and Tiedje (1979) found that a major part of gaseous N loss from soils occurs within a
few hours after wetting. In our work, we observed an initial flux ofN2 and N20 two h
following fertilization (Fig. 3 and 4), which is consistent with the finding that microbial
production ofN20 has been detected within 30 min following wetting of a dry soil
(Rudaz et aI., 1991). A large flux ofN2 and N20 occurred three d after fertilization
(DAF) in the spring experiment (Fig. 3) following a major rainfall event, although Freney
et aI. (1979), Rice and Smith (1982) and J0rgensen et aI. (1998) have observed that N20
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fluxes following rainfall could be caused by the release of soil-adsorbed N20 due to
water penetration. Nitrous oxide is fairly soluble in water (1.0 L L-1 water at 5°C), and
drying of the soil surface may release previously dissolved N20 from soil water (Dowdell
et aI., 1979; Minami and Ohsawa, 1990); however, this would not be the case with N2 as
this gas is not as water soluble (0.015 L L-1 water at 25°C). As the measured atmospheric
volume increased beginning four DAF in the spring experiment (Fig. 3), we observed a
rapid decrease in denitrification that was likely due to soil drainage, permitting the
diffusion of O2 into soil pores.
Nitrogen losses through denitrification vary greatly and are highly variable over
relatively small areas, depending on N03 levels, moisture status of the soil, available
organic matter, microbial distribution, and temperature (Engler et aI., 1976; Robertson
and Tiedje, 1987; Saad and Conrad, 1993). Spatial and temporal variability ofN20 and
N2 emission from field soils and grasslands has been well documented by several
investigators (e.g., Rolston et at, 1978; Ryden et at, 1978; Robbins et aI., 1979; Bremner
et aI., 1980; Bremner et aI., 1981; Mosier et aI., 1981; Blackmer et aI., 1982; Parkin,
1993; Velthof et aI., 1996) and greatly complicates quantification ofN20 and N2
emissions in the field. Large differences in the emission rate ofN2 and N20 between Fig.
3 and 4 were observed and can be attributed, at least in part, to two factors; higher soil
temperatures in the summer months and an 8.9-cm rainfall event four DAF in the summer
experiment. Approximately 8.5% ofLFN was lost as N2 or N20 during and three d
following this rainfall event while emission was increased by 70% when soil-derived N
was included. By comparison, only 2.7% ofLFN was lost as N2 or N20 for the entire
six-wk spring experiment. Average daily soil temperatures (Fig. 5) can also help explain
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the large differences in emission ofN2 and N20 when comparing the two experiments, in
that soil temperatures increased throughout the month of July presumably leading to more
active microbial populations. Therefore, with anaerobic conditions from the heavy
rainfall event, higher soil temperatures, and a readily available supply ofN03 from the
applied fertilizer, conditions were ideal for denitrification.
During both the spring and summer experiments, plots were irrigated to replace
80% of the PET; moreover, the intensity of the rainfall event four DAF in the summer
effectively sealed the soil surface (standing water present) causing a lag in N2 and N20
emission with the largest emission rate occurring one d following the rainfall event (Fig.
4). Letey et al. (1980) cautioned that very slow diffusion ofN2 and N20 in flooded soil
might restrict the evolution of 15N-Iabeled gases formed in the soil by denitrification.
Similarly, Mulvaney and Kurtz (1984) reported a lag period between application of water
and evolution ofN2 and N20 with maximal evolution occurring 2 to 9 days after water
was applied. This long lag period observed by Mulvaney and Kurtz (1984) can be
attributed to their experimental design, in that the soil cores from which N2 and N20
fluxes were measured were sealed at the bottom, preventing drainage and prolonging
saturation.
There is evidence that plants affect the flux ofN2 and N20 (e.g., Reddy and
Patrick, 1986; Haider et aI., 1990; Mosier et aI., 1990; Chang, et aI., 1998; Chen et aI.,
1999). In a field study, Mosier et aI. (1990) found greater recovery ofN2 and N20 from
15N-Iabeled urea when atmospheric samples were collected by placing chambers over,
rather than between, rice plants in flooded soil. This suggests that the plants acted as a
conduit for gas exchange. In our work, a lag in gas flux was observed (day 5 in Fig. 4),
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but emission ofN2 and N20 was detected while standing water was visible within the
chambers, suggesting that N2 and N20 formed in flooded soil by denitrification may have
been transported from the soil to the atmosphere through Kentucky bluegrass plants.
Kentucky bluegrass, apparently, does not contain aerenchyma that are generally found in
root systems of wetland (y.Iaisel and Eshel, 1991) or flood-tolerant (Drew and Stolzy,
1991) plants to conduct gases between the atmosphere and soil root zone. However,
Chen et al. (1999) found that perennial ryegrass (Lolium perenne L.) significantly
increased N20 emission rates from a saturated soil and concluded that perennial ryegrass
can serv as a conduit for N20 release from saturated soil through the transpiration stream
of the plants. The same process may account for emission ofN2 and N20 observed in out
work during periods of standing water.
Greenhouse Experiment
As previously described, a turfgrass system is much more complex than a bare
soil system, owing to the presence of roots, thatch, and aboveground biomass. To
determine if the presence of plants promote gas exchange from soil, emission rates ofN2
and N20 were compared for soils with and without Kentucky bluegrass. Figure 6 shows
the results of daily measurements ofLFN and total N evolved as N2 or N20 from 15N_
fertilized Kentucky bluegrass cores during a 3-wk experiment in the greenhouse.
Turfgrass consistently led to larger fluxes ofN2 and N20 with LFN emission totaling
2.37% from turfgrass and 0.91% from bare soil (Fig. 6). These results are in accordance
with Larsson et al. (1998) where emission ofN20 from a grass sward (6 kg N20-N ha-1)
greatly exceeded the emission from bare soil (0.2 kg N20-N ha-1). As with the field
studies, emission ofN2 and N20 were most extensive one or two d following fertilization
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and decreased as the soil drained. Aerobic and anaerobic microsites can develop within
the same soil aggregate (Hejberg et aI., 1994) and N03 reduction can occur as soils drain
(Smith, 1980; Renault and Stengel, 1994), which may account for the fact that in our
work, emission ofN2 and N20 slowed but did not diminish immediately after irrigation.
With a turfgrass system, roots are able to extract water from deeper in the soil profile and
may lead to less rapid drying of the soil surface. In contrast to turf, bare soil dries faster
from the soil surface downward and with less frequent irrigation in the present study, the
soil surface was visibly drier therefore more aerobic which resulted in lower rates of
denitrification.
The Ne technique employed to measure the atmospheric volume confined within
a closed cylinder (see chapter 2) was developed to improve the accuracy achieved in
direct measurements of denitrification by not only measuring the volume of air above the
soil surface, but also measuring the soil-air volume. Therefore, soil moisture content can
be monitored by measuring the atmospheric volume confined within the closed chamber,
whereby, as the soil water content increases, the soil-air will be displaced and
correspondingly, the atmospheric volume will decrease. During the time immediately
following fertilization with KN03, N03 is readily available for loss if anaerobic
conditions exist. Moreover, fertilizers were applied in solution with approximately 0.5
cm of water and since irrigation of highly maintained turfgrass keeps the soil profile near
field capacity, anaerobic microsites may have been formed leading to short-term anoxia
(Sexstone et aI., 1985; H0jberg et aI., 1994). Marked decreases in atmospheric volume
coincided with emission ofN2 and N20 (Fig. 3 to 5). For example, three rainfall events
during the spring experiment occurred on days 23 through 25, that created conditions
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conducive for denitrification of soil N03 (detectable because unlabeled soil N pooled
with LFN) and the atmospheric volume during this time decreased from approximately
2.4 to 1.6 L (Fig. 3). Similar events took place during the summer experiment (Fig. 4)
when three to five DAF, atmospheric volume decreased from approximately 2.4 to 2.0 L.
Fertilizer Effects on Denitrification
Creeping bentgrass often receives weekly foliar applications of soluble fertilizer
at low rates to control the amount ofN available for plant uptake. A field study was
initiated to study emission rates ofN2 and N20 and the effect of weekly fertilization with
two soluble sources of fertilizer on creeping bentgrass turf Figure 7 shows the rates of
LFN and total N2 and N20 emission from plots fertilized weekly with 9.8 kg N ha-1 as
KN03 or urea.
For the first three applications of fertilizer, emission ofLFN and total N as N2 was
consistently greater for plots treated with KN03 than with urea (Fig. 7), because in order
for an ~-based fertilizer to be denitrified, nitrification must occur to convert Nl4 to
N03 or N02. With the large readily available supply of organic C in the thatch layer, it is
likely that following hydrolysis of the urea, considerable immobilization ofNHt occurred
leading to less substrate available for nitrification. Bowman et al. (1989) reported that
turfgrass fertilized at 50 kg N ha-1, supplied as N03 or NH4, can deplete the applied N
within 48 h after application. In the present study, the creeping bentgrass turf had not
been fertilized for over 4 wk, so in addition to immobilization and nitrification ofN14,
plant uptake ofNlI4 and N03 could account for low emission rates ofN2 during
denitrification. During the latter 2 wk of the experiment, the urea-treatment evolved
more LFN and total N as N2 which can be attributed to the accumulation ofN03 through
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nitrification of~, which provided substrate for denitrification. With three weekly
applications of fertilizer, the N deficiency observed prior to the experiment was probably
corrected, which would result in lower rates of plant uptake a larger quantity ofN03 that
could have denitrified.
The rise in soil pH that accompanies hydrolysis of urea is only temporary due to
the acidity generated from nitrification of~ and because of the buffering capacity of
soil. It is generally accepted that the increased concentration ofN03 from nitrification of
~, and the short-term acidity produced by nitrification should favor production ofN20
relative to N2 (Blackmer and Bremner, 1978; Koskinen and Keeney, 1982; Ottow et aI.,
1985; Breitenbeck and Bremner, 1986; Weier et aI., 1993). However, in our work, no
N20 emissions were detected from soil under turfgrass treated with urea. Similar results
were reported by Maggiotto et al. (2000) for a turfgrass system where urea fertilization
resulted in very low emission rates ofN20 (0.05 to 0.33% of applied N) determined by a
micrometeorological technique. The results reported in our work contrasts those reported
by Breitenbeck et aI. (1980) and Breitenbeck and Bremner (1986), who report that N20
emissions occur from urea fertilized soils. No clear explanation can be offered to account
for this difference, but further work is clearly warranted before defmite conclusions can
be reached regarding the impact of turf grass N fertilization on N20 emission.
In contrast to urea, N20 evolution did occur on turf receiving applications of
KN03, but was only detected the day of fertilization (Fig. 7). The increased
concentration ofN03 immediately following fertilization would have promoted
production ofN20 relative to N2 during denitrification (Firestone et aI., 1979), as a high
N03
concentration inhibits the conversion ofN20 to N2 (Weier et aI., 1993). The mole
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fraction ofN20 [calculated as N20-N/(N2+N20)-N] decreased with each successive
application ofKN03 fertilizer from 0.41 to 0.11. This latter fmding can be attributed to
the increase in irrigation frequency the last two wk of the experiment, since N2 emission
during denitrification is favored by an increase in the degree of anaerobicity (Weier et aI.,
1993).
The results presented in this study represent the fIrst attempt to measure
denitrification from turfgrass using 15N-Iabeledfertilizer. Field measurements suggest
that N2 losses can affect N-fertilization practices, in that gaseous N loss occurs regularly
throughout the summer with large fluxes ofN2 and N20 after heavy rainfalVirrigation
events. Nitrate-based fertilizers are more susceptible to denitrification than ammonium-
based fertilizers if irrigation is over-applied or if a large rainfall event occurs soon after
application. Inaddition, we demonstrated that even with standing water, N2 and N20
losses occur, suggesting that plants act as a conduit for gas exchange between the soil and
the atmosphere. Nitrous oxide emission rates from N fertilizer applied to turfgrass will
depend largely on the source of fertilizer, and additional studies of fertilizer-induced N20
and N2 emissions from turf over a wide range of conditions are necessary to understand
the dynamics of the turfgrass N cycle.
REFERENCES
Blackmer, A.M., and J.M. Bremner. 1978. Inhibitory effect of nitrate on reduction of
N20 to N2 by microorganisms. Soil BioI. Biochem. 10:187-191.
Blackmer, A.M., 8.0. Robbins, and J.M. Bremner. 1982. Dirunal variability in rate of
emission of nitrous oxide from soils. Soil Sci. Soc. Am. 1. 46:937-942.
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Bollag, J.M., M.L. Grcut, and B. Bollag. 1970. Denitrification by isolated soil bacteria
under various environmental conditions. Soil Sci. Soc. Am. Proc. 34:875-879.
Bowman, D.C., J.L. Paul, W.B. Davis, and S.H. Nelson. 1989. Rapid depletion of
nitrogen applied to Kentucky bluegrass turf. J. Am. Soc. Hort. Sci. 114:229-233.
Breitenbeck, G.A., A.M. Blackmer, and J.M. Bremner. 1980. Effects of different
nitrogen fertilizers on emission of nitrous oxide from soil. Geophys. Res. Lett.
7:85-88.
Breitenbeck, G.A., and J.M. Bremner. 1986. Effect of various fertilizers on emission of
nitrous oxide from soils. BioI. Fertil. Soils 2:195-199.
Bremner, J.M., G.A. Breitenbeck, and A.M. Blackmer. 1981. Effect ofnitrapYrin on
emission of nitrous oxide from soil fertilized with anhydrous ammonia. Geophys.
Res. Lett. 8:353-356.
Bremner, J.M., S.G. Robbins, and A.M. Blackmer. 1980. Seasonal variability in
emission of nitrous oxide from soil. Geophys. Res. Lett. 7 :641-644.
Chang, C., H.H. Hanzen, C.M. Cho, and E.M. Nakonechny. 1998. Nitrous oxide
emission through plants. Soil Sci. Soc. Am. J. 62:35-38.
Chen, X., P. Boechx, S. Shen, and o. Van Cleemput. 1999. Emission ofN20 from rye
grass (Lolium perenne L.) BioI. Fertil. Soils 28:393-396.
Denmead, G.T. 1979. Chamber systems for measuring nitrous oxide emission from soils
in the field. Soil Sci. Soc. Am. 1. 43:89-95.
Denmead, G.T., J.R. Freney, and J.R. Simpson. 1979. Studies of nitrous oxide emission
from a grass sward. Soil Sci. Soc. Am. J. 43:726-728.
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Dowdell, R.J., IR. Burford, and R. Crees. 1979. Losses of nitrous oxide dissolved in
drainage water from agricultural land. Nature 278:342-343.
Drew, M.C., and L.R. Stolzy. 1991. Growth under oxygen stress. p.331-335. In Y.
Waisel et al. (ed.) Plant roots: The hidden halt: Marcel Dekker, New York.
Engler, R.M., D.A. Antie, and W.H. Patrick, Jr. 1976. Effect of dissolved oxygen on
redox potential and nitrate removal in flooded swamp and marsh soils. J.
Environ. Qual. 5:230-235.
Firestone, M.K., M.S. Smith, R.B. Firestone, and J.M. Tiedje. 1979. The influence of
nitrate, nitrite, and oxygen on the composition of gaseous products of
denitrification in soil. Soil Sci. Soc. Am. J. 43:1140-1144.
Freney, J.R., a.T. Denmead, and J.R. Simpson. 1979. Nitrous oxide emission from soils
at low moisture contents. Soil BioI. Biochem. 11:167-173.
Haider, K., O. Heinemeyer, and A.R. Mosier. 1990. Direct and indirect effects of plants
on denitrification. Mitt. Deutsch. Bodenk. Gesellschaft. 60: 101-108.
Hejberg, 0., N.P. Revsbech, and J.M. Tiedje. 1994. Denitrification in soil aggregates
analyzed with microsensors for nitrous oxide and oxygen. Soil Sci. Soc. Am. J.
58:1691-1698.
Hutchinson, G.L., and A.R. Mosier. 1981. Improved soil cover method for field
measurement of nitrous oxide fluxes. Soil Sci. Soc. Am. J. 45 :311-316.
Jergensen, R.N., B.J. Jergensen, and N.E. Nielsen. 1998. N20 emission immediately
after rainfall in a dry stubble field. Soil BioI. Biochem. 30:545-546.
Koskinen, W.C., and D.R. Keeney. 1982. Effect of pH on the rate of gaseous products
of denitrification in a silt loam soil. Soil Sci. Soc. Am. J. 46:1165-1167.
-
57
Larsson, L., M. Ferm, A. Kasimir-Klemedtsson, L. Klemedtsson, M. Esala, and H.
Kirchmann. 1998. Ammonia and nitrous oxide emissions from grass and alfalfa
mulches. p.41-46. In M. Esala (ed.) Proc. nutrient cycling in agroecosystems.
lJppsal~Svveeden.
Letey, J., W.A. Jury, A. Hadas, and N. Valoras. 1980. Gas diffusion as a factor in
laboratory incubation studies. J. Environ. Qual. 9:223-227.
Maggiotto, S.R., J.A. Webb, C. Wagner-Riddle, and G.W. Thurtell. 2000. Nitrous and
nitrogen oxide emissions from turfgrass receiving different forms of nitrogen
fertilizer. J. Environ. Qual. 29:621-630.
Mancino, C.F., W.A. Torello, and D.J. Wehner. 1988. Denitrification losses from
Kentucky bluegrass sod. Agron. J. 80:148-153.
Miltner, E.D., B. E. Branham, E.A. Paul, and P.E. Rieke. 1996. Leaching and mass
balance of 15N-Iabeled urea applied to a Kentucky bluegrass turf. Crop Sci.
36:1427-1433.
Minami, K., and O. Ohsavva. 1990. Emission of nitrous oxide dissolved in drainage
water from agricultural land. p.503-509. In Bouvvman A.F. (ed) Soils and the
greenhouse effect. John Wiley and Sons, Nevv York.
Mosier, A.R., M. Stillvvell, N.J. Parton, and R.G. Woodmansee. 1981. Nitrous oxide
emissions from a native shortgrass prairie. Soil Sci. Soc. Am. 1. 45:617-619.
Mosier, A.R., S.K. Mohanty, A. Bhadrachalam, and S.P. Chakravorti. 1990. Evolution
of dinitrogen and nitrous oxide from the soil to the atmosphere through rice
plants. BioI. Fertil. Soils 9:61-67.
-
58
Mulvaney, R.L., and C.W. Boast. 1986. Equations for determination ofnitrogen-15
labeled dinitrogen and nitrous oxide by mass spectrometry. Soil Sci. Soc. Am. J.
50:360-363.
Mulvaney, R.L., and L.T. Kurtz. 1982. A new method for determination of 15N-Iabeled
nitrous oxide. Soil Sci. Soc. Am. J. 46:1178-1184.
Mulvaney, R.L., and L.T. Kurtz. 1984. Evolution of dinitrogen and nitrous oxide from
nitrogen-IS fertilized soil cores subjected to wetting and drying cycles. Soil Sci.
Soc. Am. 1. 48:596-602.
Mulvaney, R.L., S.A. Khan, and C.S. Mulvaney. 1997. Nitrogen fertilizers promote
denitrification. BioI. Fertil. Soils 24:211-220.
Norman, R.J., L.T. Kurtz, and F.J. Stevenson. 1987. Solubilization of soil organic
matter by liquid anhydrous ammonia. Soil Sci. Soc. Am. J. 51:809-812.
Ottow, J.e.G., I Burth-Gebauer, and M.E. EI Demerdash. 1985. Influence of pH and
partial oxygen pressure on the N20-N to N2 ratio of denitrification. p. 101-120.
In H.L. Goltennan (ed.) Denitrification in the nitrogen cycle. Plenum Press, New
York.
Parkin, T.B. 1993. Spatial variability of microbial processes in soil- a review. J.
Environ. Qual. 22:409-417.
P I E A d F E Clark 1989. Soil microbiology and biochemistry. Academic Press,au, .. , an ...
San Diego, CA.
Prather, M., R. Derwent, D. Ehhalr, P. Fraser, E. Sanhueza, and X. Zhou. 1995. Other
trace gases and atmospheric chemistry. Intergovernmental Panel on Climate
-
59
Change. Climate change 1994: Radiative forcing of climate change. Cambridge
University Press, Cambridge, UK.
Reddy, K.R., and W.H. Patrick. 1986. Denitrification losses in flooded rice fields. Fert.
Res. 9:99-116.
Renault, P., and P. Stengel. 1994. Modelling oxygen diffusion in aggregated soils: I.
Anaerobiosis inside the aggregates. Soil Sci. Soc. Am. J. 58:1017-1023.
Rice, C.W., and M.S. Smith. 1982. Denitrification in no-till and plowed soils. Soil Sci.
Soc. Am. 1. 46: 1168-1173.
Robbins, S.O., A.M. Blackmer, and J.M. Bremner. 1979. Spatial and dumal variability
in emission of nitrous oxide from soils. p.37. In Agronomy Abstracts. ASA,
Madison, WI.
Robertson, O.P., and J.M. Tiedje. 1987. Nitrous oxide sources in aerobic soils:
Nitrification, denitrification, and other biological processes. Soil BioI. Biochem.
19:187-193.
Rolston, D.E., D.L. Hoffman, and D.W. Toy. 1978. Field measurement of
denitrification. I.Flux ofN2 and N20. Soil Sci. Soc. Am. J. 42:863-869.
Rudaz, A.O., E.A. Davidson, and M.K. Firestone. 1991. Sources of nitrous oxide
production following wetting of dry soil. FEMS Microbiol. Ecol. 85:117-124.
Ryden, J.e., L.F. Lund, and D.D. Focht. 1978. Direct in-field measurement of nitrous
oxide flux from soils. Soil Sci. Soc. Am. J. 43:110-118.
Saad, Omar A.L.O., and R. Conrad. 1993. Temperature dependence of nitrification,
denitrification, and turnover of nitric oxide in different soils. BioI. Fert. Soils
15:21-27.
-
60
Schnabel, R.R., and W.L. Stout. 1994. Denitrification loss from two Pennsylvania
floodplain soils. J. Environ. Qual. 23:344-348.
Schwarz, J., M. Kapp, G. Benckiser, and J.C.G. Ottow. 1994. Evaluation of
denitrification losses by the acetylene inhibition technique in a permanent
ryegrass field fertilized with animal slurry or ammonium nitrate. BioI. FertiI.
Soils 18:333-336.
Sen, S., and P.M Chalk. 1994. Solubilization of soil organic N by alkaline-hydrolysing
N fertilizers. Fert. Res. 38: 131-139.
Sexstone, A.1., T.B. Parkin, and J.M. Tiedje. 1985. Temporal response of soil
denitrification rates to rainfall and irrigation. Soil Sci. Soc. Am. J. 49:99-103.
Smith, K.A. 1980. A model of the extent of anaerobic zones in aggregated soils, and
potential application to estimates of denitrification. J. Soil Sci. 31 :263-277.
Smith, M.S., and J.M. Tiedje. 1979. Phases of denitrification following oxygen
depletion in soil. Soil BioI. Biochem. 11:261-267.
Starr, J.L., and H.C. DeRoo. 1981. The fate of nitrogen fertilizer applied to turfgrass.
Crop Sci. 21 :531-536.
Stevenson, F.J., and M.A. Cole. 1999. Cycles of soil. Carbon, nitrogen, phosphorus,
sulfur, micronutrients. 2nd ed. John Wiley and Sons, New York.
Tenuta, M., and E.G. Beauchamp. 1995. Denitrification following herbicide application
to a grass sward. Can. 1. Soil Sci. 76:15-22.
Van Cleemput, 0., A. Vermoesen, C. De Groot, and K. Van Ryckeghem. 1994. Nitrous
oxide emission out of grassland. Environ. Monit. Assess. 31: 145-152.
-
61
Velthof, G.F., A.B. Brader, and O. Oenema. 1996. Seasonal variations in nitrous oxide
losses from managed grasslands in The Netherlands. Plant Soil 181:262-274.
Waisel, Y., and A. Eshel. 1991. Multiform behavior of various constituents of one root
system, p. 39-52. In Y. Waisel et al. (ed.) Plant roots: The hidden half. Marcel
Dekker, New York.
Weier, K.L., J.W. Doran, J.F. Power, and D.T. Walters. 1993. Denitrification and the
dinitrogen/nitrous oxide ratio as affected by soil water, available carbon, and
nitrate. Soil Sci. Soc. Am. J. 57:66-72.
Yoshinari, T., R. Haynes, and R. Knowles. 1977. Acetylene inhibition of nitrous oxide
reduction and measurement of denitrification and nitrogen fixation in soils. Soil
Biol. Biochem. 9:177-183.
ACKNOWLEDGMENTS
We thank the United States Golf Association for partial support for this project.
We thank Drs. Khan and Gardner for their laboratory and statistical guidance and Joe
Meyer, James Abel, Cindy Dembs, and Yoko Haneda deCaussin for their technical
support. In addition, we thank the Illinois State Water Survey for providing potential
evapotranspiration data.
FIGURE CAPTION
Fig 3. Daily measurements of LFN and total N evolved as N2 and N20 from Kentucky
bluegrass cores fertilized with 15N-labeled KN03 during the spring experiment in
the field. Mass spectrometric results from the three, 3-h flux measurements from
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62
within each replication were summed, and values are reported as a mean of two
replications. Daily atmospheric volume measurements were performed using the
Ne technique during collection ofN2 and N20. Volume measurements are
reported in mL as means of the two replications. Standard errors are reported for
each calculated mean.
Fig 4. Daily measurements ofLFN and total N evolved as N2 and N20 from Kentucky
bluegrass cores fertilized with 15N-labeledKN03 during the summer experiment
in the field. Mass spectrometric results from the three, 3-h flux measurements
from within each replication were summed, and values are reported as a mean of
two replications. Daily atmospheric volume measurements were performed using
the Ne technique during collection ofN2 and N20. Volume measurements are
reported in mL as means of the two replications. Standard errors are reported for
each calculated mean.
Fig. 5. Average daily soil temperature readings reported from May through September
1999.
Fig. 6. Daily measurements ofLFN and total N evolved as N2 and N20 from Kentucky
bluegrass cores and bare soil cores fertilized with IsN-labeled KN03 in the
greenhouse. Values are reported as a mean of two replications. Daily
atmospheric volume measurements were performed using the Ne technique
during collection ofN2 and N20. Volume measurements are reported in mL as
means of the two replications. Standard errors are reported for each calculated
mean.
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63
Fig. 7. Daily measurements ofLFN and total N evolved as N2 and N20 from creeping
bentgrass cores fertilized with 15N-IabeledKN03 or urea in the field. Weekly
fertilizer applications were made from 18 July through 21 August 2000. Values
reported are means of the two replications. Standard errors are reported for each
calculated mean.
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64
y 3h Z g <
< L L
I l l H
CO CO
LU
1 _E3_ JL 1.
N20
LFN Loss Total Loss
14 21 28
DAYS AFTER FERTILIZATION
Fig. 3
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65
~ LFNLoss~ Total Loss
7 14
N2~ LFNLoss-0- Total Loss
21 28
DAYS AFTER FERTiliZATION
Fig. 4
-
- 3200 Spring Summer-W experiment experiment0:::J 28I-
~WD. 24~WI-.J0 20UJ>.J
-
67
21
-+- Bare Soil-0- Turf
LFN~ N2 Turf-0- N2 Bare Soil~ N20Turf-9- N20 Bare Soil
Total Loss__ N
2Turf
-0- N2 Bare Soil-y- N20 Turf-v- N20 Bare Soil
147
DAYS AFTER FERTILIZATION
Fig. 6
oo
2
3600
0 - 3200Q: -IW E:t:- 2800a. wen ~0 :J~ -I 2400I- 0
2000
0.8
-E 0.6(.)-Z0 0.4~(!)
.....
~ 0.2a:-0.0
6
-
68
.:0:
1111
--- KN03-0- Urea
--- KN03-0- Urea
--- KN03-0- Urea
--- KN03-0- Urea
- 1.6E(,)- 1.2
:J~ 0.8..J-«I-LL« 0.4zC>-0:=~~ 0.0
0.75
0.50
0.25
0.00
2.0
1.5
-~ 1.0.en~E 0.5ZC') 0.0:J.-W 0.75I-~Z 0.500UJ~ 0.25~W
0.00
1.25
1.00
0.75
0.50
0.25
0.00a 7
DAYS AFTER INITIAL FERTiliZATIONFig. 7