Research Notes
The Impact of pH on Nitrogen Retention
in Laboratory Analysis of Broiler Litter1
R. P. BURGESS, J. B. CAREY,2 and D. J. SHAFER
Department of Poultry Science, Texas A&M University, College Station, Texas 77843-2472
ABSTRACT
Land application of broiler litter must
fully regard agronomic and environmental issues, which
requires increased precision in all aspects of land
application of poultry litter. Previous researchers note
that litter experiences significant nitrogen loss due to
ammonia volatilization during the drying process.
Others note that pH of poultry houses and litter
significantly affects nitrogen loss due to ammonia
volatilization. Recent work shows that acidifying agents
effectively reduce ammonia generation in poultry
production facilities. This concept is used in this study
to adjust the pH of broiler litter samples prior to drying
to reduce nitrogen loss during the drying process.
Samples from four sources were used. Untreated litter
was compared to litter treated with Al2(SO4)3, (10:1 wet
weight basis) either in small (10 g) or large (100 g
batches). Both Al2(SO4)3 treatment methods significantly
lowered litter sample pH. No significant differences
were observed in litter moisture analysis values. Regardless of source, litter treated in small batches had
significantly higher nitrogen values than untreated litter.
Large batches of treated litter did not consistently have
higher nitrogen values than untreated litter. Treatment
of litter samples with Al2(SO4)3 prior to drying resulted
in more accurate quantification of nitrogen in litter,
which can ultimately result in more accurate utilization
of litter in agronomic applications.
(Key words: broiler, litter, nitrogen analysis, ammonia, volatilization)
1998 Poultry Science 77:1620–1622
INTRODUCTION
With increasing emphasis on accurate agronomic land
application of nutrients from broiler litter, greater
demands are being placed on the analytical processes
associated with litter chemical characterization. There is
a need for increased accuracy in every aspect of land
application of poultry litter. Laboratories typically ovendry litter prior to N2 analysis without accounting for
ammonia loss during the process. Derikx et al. (1994)
reported that litter samples lose nearly all ammonia
originally present. Parker et al. (1959) reported nitrogen
losses during the drying process of 11.6 and 17.0% in
broiler and layer manure, respectively. Wood and Hall
(1991) compared various drying methods and reported
nitrogen losses during drying to range from 12 to 15%.
When laboratory analysis values that have experienced
N loss are used to calculate litter land application rates,
Received for publication February 26, 1998.
Accepted for publication June 24, 1998.
1The use of trade names in this publication does not imply
endorsement by the Texas Agricultural Experiment Station nor
criticism of similar ones not mentioned.
2To whom correspondence should be addressed:
[email protected]
3Sigma Chemical Co., St. Louis, MO 63178-9916
it is likely that more nitrogen is applied than is
estimated.
Reece et al. (1979) demonstrated that the pH of broiler
litter influences ammonia levels in poultry rearing
facilities. Ammonia release was negligible when litter
pH was below 7. However, as pH approached 7,
ammonia release began. Thus, as the pH of litter
decreases, ammonia loss decreases. Aluminum sulfate
[Al2(SO4)3] and numerous other acidic compounds are
effective in lowering litter pH and reducing ammonia
volatilization in commercial broiler houses (Moore et al.,
1995). However, this information has never been given
consideration in laboratory analysis of broiler litter
samples. Derikx et al. (1994) reported that at pH 7 or
higher, nearly all ammonia is lost during the drying
process. They further stated that complete fixation of
ammonia is possible during dry matter determination if
the pH is as low as 4 to 5. At this pH, they reported less
than 0.01% of the ammonia exists as NH3.
Control of ammonia loss during the drying process
will provide for more accurate measurement of litter
nitrogen and ultimately a more accurate application of
litter in agronomic practices. The objective of this study
was to examine the effects of adding aluminum sulfate
to litter samples prior to drying on the nitrogen analysis.
Aluminum sulfate was selected because it is available as
a dry powder and is relatively inexpensive.3
1620
1621
RESEARCH NOTE
TABLE 1. Effect of Al2(SO4)3 treatment of broiler litter sample pH
Litter/Al2(SO4)3
2
Litter source1
Litter only
Small batch3
Large batch3
Pooled SEM
Composted
Pallet, 3.5 wk
Pallet, 6 wk
Rice hull, seven flocks
4.92a
6.51a
5.62a
7.47a
3.92a
4.16b
3.84b
5.75b
....
4.36b
3.69b
4.43b
0.471
0.096
0.085
0.411
within a row with no common superscript differ significantly (P ≤ 0.05).
of two replicates (n = 2).
2Litter and Al (SO ) mixed 10:1 on wet weight basis.
2
4 3
3Small = litter and Al (SO )
2
4 3 mixed in 10-g aliquots: Large = litter and Al2(SO4)3 mixed in
100-g aliquots.
a,bMeans
1Mean
TABLE 2. Effect of Al2(SO4)3 treatment on broiler litter sample moisture
Litter/Al2(SO4)3
Litter
source1
Litter only
Small
18.96a
20.34a
28.84a
26.32a
18.57b
15.83a
24.34a
26.08a
batch3
2
Large batch3
Pooled SEM
....
18.36a
26.85a
23.51a
0.089
3.036
2.146
4.302
(%)
Composted
Pallet, 3.5 wk
Pallet, 6 wk
Rice Hull, seven flocks
within a row with no common superscript differ significantly (P ≤ 0.05).
of three replicates (n = 3).
2Litter and Al (SO ) mixed 10:1 on wet weight basis.
2
4 3
3Small = litter and Al (SO )
2
4 3 mixed in 10-g aliquots. Large = litter and Al2(SO4)3 mixed in
100-g aliquots.
a,bMeans
1Mean
MATERIALS AND METHODS
Four trials were conducted using litter from four
different sources. The first source was a mixture of
composted litter, collected from several commercial
broiler farms. This composite sample included rice hulls
and pine shavings as bedding material. The second
source, collected from the Texas A&M University
Poultry Research Center, used shredded pallets as a
bedding material. Separate samples of this litter were
collected after 3.5 and 6 wk of broiler growth. The fourth
source was collected from a commercial broiler farm
after seven flocks and used rice hulls as a bedding
material.
Untreated litter was compared to two methods of
Al2(SO4)3 mixing, small and large batch methods. In
each method, a 10:1 litter:Al2(SO4)3 ratio (wet weight)
was mixed prior to the drying process. In the small
batch method 10 g of litter and 1 g of Al2(SO4)3 were
mixed in the drying pan immediately prior to drying.
The large batch method mixed 100 g of litter and 10 g of
Al2(SO4)3. The large sample was subsequently divided
into 10-g samples. Litter samples were not ground or
otherwise manipulated prior to mixing. To assure a
uniform mixture and accurate analysis, the samples
4Thelco
5Model
Model 24, Precision Scientific, Chicago, IL 60647.
FP-428, Leco Corp., St. Joseph, MI 49085.
were mixed thoroughly prior to the drying process. In
the first trial, which utilized the composted litter, only
untreated litter and the small batch treatment method
were compared.
Samples from each trial were analyzed for pH,
moisture, and nitrogen. The pH of duplicate samples of
each treatment was measured within 2 h of mixing with
Al2(SO4)3, using a mixture of 20 mL of distilled H2O and
1 g of the sample. This mixture was stirred to obtain a
homogeneous mixture prior to measuring sample pH. In
each trial, moisture content was determined for three
samples per treatment by simultaneously drying for 24 h
at 100 C in a drying oven4 within 2 h of mixing with
Al2(SO4)3. Three samples of Al2(SO4)3 alone were also
dried to determine the weight loss attributable to the
addition of this compound. After drying, the samples
were weighed, to the nearest 0.001 g. The weight loss of
Al2(SO4)3 was subtracted from the total sample weight
loss from each treated sample. Samples were immediately transferred to a desiccator for storage prior to
nitrogen analysis, which was done within 24 h of
drying. In each trial, nine 0.5-g samples from each
treatment were used for nitrogen analysis, with a LECO5
Nitrogen Determinator. The samples were ground prior
to nitrogen analysis. Analysis of Al2(SO4)3 for nitrogen
found negligible nitrogen content. The nitrogen values
of the treated samples are expressed as a percentage of
the litter dry matter, which has been adjusted for the
presence of the Al2(SO4)3.
1622
BURGESS ET AL.
TABLE 3. Effect of Al2(SO4)3 treatment on broiler litter sample nitrogen
Litter/Al2(SO4)3
Litter source1
Litter only
Small Batch3
Composted
Pallet, 3.5 wk
Pallet, 6 wk
Rice Hull, seven flocks
4.13b
2.85b
3.37b
3.77c
4.87a
3.54a
3.88a
4.59a
2
Large batch
Pooled SEM
....
3.10b
3.69ab
4.37b
0.141
0.113
0.124
0.063
(%)
within a row with no common superscript differ significantly (P ≤ 0.05).
of nine replicates (n = 9).
2Litter and Al (SO ) mixed 10:1 on wet weight basis.
2
4 3
3Small = litter and Al (SO )
2
4 3 mixed in 10-g aliquots. Large = litter and Al2(SO4)3 mixed in
100-g aliquots.
a,bMeans
1Means
Data were analyzed using the General Linear Models
procedure of SAS (SAS Institute, 1990). Mean separation was accomplished utilizing the PDIFF option (pairwise t tests) of the General Linear Models procedure.
Statements of statistical significance are based on P <
0.05.
RESULTS AND DISCUSSION
Addition of Al2(SO4)3 by the small batch method did
not significantly affect sample pH in the composted
litter trial. Among all other sources, addition of
Al2(SO4)3 by either the small or large batch method
significantly reduced sample pH (Table 1). Sample pH
was not different between small or large batch methods
in any trial. The pH of the untreated samples was above
5.0 in all cases. Derikx et al. (1994) reported that samples
should be below 5.0 to facilitate complete fixation of
nitrogen. Among treated samples, only the small batch
method of the rice hull, seven-flock litter was above pH
5.0. Ammonia volatilization may occur in the samples
with pH above pH 5.0.
Any reduction in ammonia volatilization that the
treatments may have affected would not be detectable
by gravimetric methods of moisture determination.
Therefore, litter moisture analysis should not be influenced by Al2(SO4)3 treatment. Litter moisture analysis
was significantly different between the samples utilizing
the composted litter source (Table 2). Al2(SO4)3 treatment reduced the amount of weight lost in the drying
process. Whereas some of this may be attributable to
nitrogen retention during the drying process, it does not
fully explain the difference. Among all other samples,
there were no differences in litter sample moisture.
Regardless of litter source, treatment of litter samples
with Al2(SO4)3 by the small batch method resulted in
significantly higher nitrogen values (Table 3). Treatment
with Al2(SO4)3 by the large batch method did not
consistently result in significantly higher nitrogen analysis, perhaps due to incomplete mixing with this method.
This result confirms that as a result of lower pH, the
treated samples had less ammonia loss, which in turn
resulted in higher nitrogen yields after drying. Current
recommendations for utilization of Al2(SO4)3 to reduce
pH in broiler houses stipulate a 3-d exposure time to
allow more extensive reaction between the litter and the
Al2(SO4)3. It is possible that longer holding time prior to
analysis may have allowed even greater retention of
nitrogen especially in the large batch method.
The lower pH and higher nitrogen values observed in
the litter treated by the small batch method are
consistent with Reece et al. (1979), which involved litter
pH on poultry houses and Derikx et al. (1994), which
concerned ammonia loss in manure samples. In this
study, samples treated with Al2(SO4)3 by the small batch
method retained 13 to 20% more nitrogen than untreated samples. Compared to nitrogen losses of 11.6%
reported by Parker et al. (1959) and losses of 12 to 15%
reported by Wood and Hall (1991), it is evident that
significant quantities of nitrogen are lost in the untreated samples.
Acidification of litter samples prior to moisture
analysis will provide a more accurate measurement of
total sample nitrogen. The small batch treatment method
resulted in consistently higher nitrogen values and is the
method of choice compared to the large batch treatment
method. These techniques may ultimately result in more
accurate application of nutrients in agronomic practices
and the potential for negative environmental impacts
from excessive nitrogen application may be reduced.
REFERENCES
Derikx, P.J.L., H. C. Willers, and P.J.W. ten Have, 1994. Effects of
pH on the behavior of volatile compounds in organic manures
during dry-matter determination. Bioresource Tech. 49:41–45.
Moore, P. A., Jr., T. C. Daniel, D. R. Edwards, and D. M. Miller,
1995. Effect of chemical amendments on ammonia volatilization
from poultry litter. J. Environ. Qual. 24:293–300.
Parker, M. B., H. F. Perkins, and H. J. Fuller, 1959. Nitrogen,
phosphorus and potassium content of poultry manure and some
factors influencing its composition. Poultry Sci. 38:1154–1158.
Reece, F. N., B. J. Bates, and B. D. Lott, 1979. Ammonia control in
broiler houses. Poultry Sci. 58:754–755.
SAS Institute, 1990. SAS User’s Guide: Statistics. Version 6
Edition. SAS Institute Inc., Cary, NC.
Wood, C. W., and B. M. Hall, 1991. Impact of drying method on
broiler litter analyses. Com. Soil Sci. Plant Anal. 22:1677–1688.