JEQ Grow Your Career With ASA
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (16)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Qafoku, O.S.
Right arrow Articles by Hill, N.S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Qafoku, O.S.
Right arrow Articles by Hill, N.S.
Agricola
Right arrow Articles by Qafoku, O.S.
Right arrow Articles by Hill, N.S.
Related Collections
Right arrow Animal Waste
Right arrow Nutrient Cycling
Right arrow Water Pollution
Journal of Environmental Quality 30:217-221 (2001)
© 2001 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America

TECHNICAL REPORT
WASTE MANAGEMENT

Rapid Methods to Determine Potentially Mineralizable Nitrogen in Broiler Litter

O.S. Qafoku, M.L. Cabrera, W.R. Windham and N.S. Hill

Russell Research Center, College Station Rd, Athens, GA 30605

Corresponding author (mcabrera{at}arches.uga.edu)

Received for publication November 30, 1999.

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 SUMMARY AND CONCLUSIONS
 REFERENCES
 
Although broiler (chicken, Gallus gallus domesticus) litter has long been used as a fertilizer, estimating the rate required to supply a desired amount of plant-available N is still hampered by the lack of rapid methods to estimate potentially mineralizable nitrogen (PMN). Previous research has suggested that near infrared reflectance spectroscopy (NIRS) and certain poultry litter characteristics, such as water-soluble organic nitrogen (WSON), may be useful for estimating PMN. The objectives of this study were to evaluate NIRS and WSON as tools to estimate PMN in broiler litter. Sixty sieved (2 mm) and freeze-dried broiler litter samples were mixed with Cowarts sandy loam soil (fine-loamy, kaolinitic, thermic Typic Kanhapludult) and incubated at 25°C for 112 d. Cumulative net N mineralized with time was fitted to a single-pool exponential model to determine PMN for each broiler litter sample. The PMN values obtained were regressed against NIRS (780 to 2500 nm) and WSON measurements. We found strong relationships between measured- and NIRS-predicted PMN , and between measured PMN and WSON . These results demonstrate the feasibility of using either of these two methods to estimate PMN in broiler litter. Future work should further test both methods for their ability to estimate mineralizable N in whole, moist broiler litter under field conditions.

Abbreviations: NIRS, near infrared reflectance spectroscopy • PMN, potentially mineralizable nitrogen • WSON, water-soluble organic nitrogen


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 SUMMARY AND CONCLUSIONS
 REFERENCES
 
BROILER litter, a mixture of broiler manure and bedding material, has long been recognized as a valuable fertilizer because it contains plant nutrients such as nitrogen (N), phosphorus (P), and potassium (K). The availability of N in poultry litter is variable, however, which makes it difficult to estimate the application rate required to supply a desired amount of plant-available N (Bitzer and Sims, 1988; Gordillo and Cabrera, 1997). Consequently, the development of rapid methods to determine plant-available N would help prevent overapplications as well as underapplications of broiler litter. Overapplications may lead to contamination of water resources with soluble nutrients, whereas underapplications may result in reduced yields.

Available N in poultry litter is made up of inorganic N and mineralizable N. Inorganic N can be easily extracted and measured, but mineralizable N is much more difficult to measure. Traditional methods of determining mineralizable N in soil and organic materials can be divided into biological and chemical methods. Biological methods measure mineralizable N by incubating a sample and measuring the inorganic N released during a long period of time (Castellanos and Pratt, 1981; King, 1984; Chae and Tabatabai, 1986; Bitzer and Sims, 1988; Gale and Gilmour, 1986). In contrast, chemical methods attempt to extract a chemical fraction that is related to mineralizable N (Castellanos and Pratt, 1981; Douglas and Magdoff, 1991; Serna and Pomares, 1991). While biological methods are usually considered more accurate than chemical methods, they are also more laborious and time consuming. Thus, the development of chemical methods that are rapid and accurate would be desirable from a practical point of view. Such chemical methods may be based on the chemical composition or on the light reflectance spectra of the litter.

With regard to methods based on the chemical composition of the litter, Gordillo and Cabrera (1997) found that PMN in 15 broiler litter samples could be estimated from total N and uric acid concentrations in the litter . Their work also suggested that other easier-to-measure litter characteristics, such as WSON, may be useful for estimating PMN.

A potentially useful method based on light reflectance is NIRS, which is commonly used for the determination of molecular compounds in the agricultural, food, pharmaceutical, paper, and petrochemical industries (Clark, 1989; Malley et al., 1993). Near infrared reflectance spectroscopy has been widely used as an alternative to wet chemistry methods for analyzing lignin, protein, starch, and moisture in forages, grains, and foods (Dull and Giangiacomo, 1984; Norris et al., 1976; Osborne and Fern, 1987). Near infrared reflectance spectroscopy has also been used to determine soil texture, organic matter, total nitrogen, and N mineralization potential in soils (Al-Abbas et al., 1971; Krishnan et al., 1980; Dalal and Henry, 1986; Meyer, 1989), as well as total N, total C, and crude ash in cattle manure (Asai et al., 1994). Preliminary work by Gordillo (1995) suggested that NIRS may be useful to estimate total N and uric acid concentrations in broiler litter. Since Gordillo and Cabrera (1997) found that total N and uric acid concentrations in broiler litter could be used to estimate PMN, it follows that NIRS may be a useful tool to estimate PMN in broiler litter.

The objectives of this study were to evaluate NIRS and WSON as tools to estimate PMN in broiler litter. Regression analysis was employed to determine the relationship between NIRS or WSON measurements and PMN determined by incubation of 60 broiler litter samples with soil.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 SUMMARY AND CONCLUSIONS
 REFERENCES
 
Soil Characteristics
The soil used in the incubation was collected from the surface horizon of an area mapped as Cowarts sandy loam. A tall fescue (Festuca arundinacea Schreb.)–bermudagrass [Cynodon dactylon (L.) Pers.] pasture (typical of those currently receiving broiler litter applications) was present on that soil at the time of sampling. The field-moist soil was passed through a 4-mm sieve, mixed, and stored in plastic containers at room temperature (20–23°C) until analysis. Because the soil was at field capacity (-0.02 Mpa) at the time of sample collection, there was no need for water adjustments before incubation. Soil pH was determined in the supernatant of a 1:2.5 soil–water suspension. The soil moisture release curve was determined with a pressure plate apparatus (Klute, 1986). Particle size distribution was measured by the micropipette method (Miller and Miller, 1987) and total C and N by dry combustion (Nelson and Sommers, 1982) with a Carlo Erba (Milan, Italy) C/N Analyzer. Inorganic N was determined by extracting 5 g soil with 40 mL of 1 M KCl for 30 min, centrifuging (280 x g), and measuring NO-3 and NH+4 in the supernatant volume as described below for broiler litter extracts. Cation exchange capacity (CEC) was measured by the ammonium acetate pH 7 method (Soil Survey Staff, 1996). The soil had a pH of 5.3 and a CEC of 3.2 cmolc kg-1, and contained 776 g sand kg-1, 192 g silt (>2 µm and <50 µm) kg-1, 32 g clay (<2 µm) kg-1, 11.2 g C kg-1, 0.8 g N kg-1, 8.0 mg NH+4–N kg-1, and 2.3 mg NO-3–N kg-1.

Litter Characteristics
Broiler litter samples were collected from 99 broiler houses located in Georgia and South Carolina. All samples were combinations of broiler excreta and litter material (wood shavings or sawdust). The samples were placed in polyethylene bags and stored at 4°C until used. In the laboratory, the fresh samples were passed through a 2-mm sieve and a subsample was freeze-dried. Out of the 99 poultry litter samples collected, 60 were selected for this study based on unique spectral characteristics, as described below in the NIRS measurements section. The incubation of only 60 samples was determined by the incubator space available.

Fresh litter samples (2 g) were dried at 65°C for 48 h to determine water content. Water pH was measured in the supernatant of a 1:5 freeze-dried litter and deionized water suspension. Inorganic N was determined by extracting 0.5 g of freeze-dried litter with 40 mL 1 M KCl for 30 min and analyzing the extract with an Alpkem (Clackamas, OR) RFA-300 Autoanalyzer. The concentration of (NO-2–N + NO-3–N) in the extract was determined by the Griess–Ilosvay technique after reduction of NO-3 to NO-2 with a Cd column (Keeney and Nelson, 1982). The concentration of NH+4–N was determined by the salicylate–hypochlorite method (Crooke and Simpson, 1971). Total C and total N were measured by dry combustion of freeze-dried samples with a LECO (St. Joseph, MI) 2000 CNS analyzer.

Potentially Mineralizable Nitrogen
We used aerobic incubation of broiler litter mixed with soil to estimate PMN. The incubation procedure was modified from a procedure described by Gordillo and Cabrera (1997). Briefly, freeze-dried broiler litter was mixed with 250 g oven-dry equivalent soil at rates designed to supply 100 mg of organic N kg-1 oven-dry equivalent soil. Two replications of each soil mixture and three replications of a nonamended control were incubated in zip-lock polyethylene bags (18 x 18 cm; 0.045 mm thick) inside three glass boxes (48 x 27 cm) held at 25 ± 2°C for 112 d. Humidified air was circulated through the glass boxes at 2 L min-1. Samples were aerated every day during the first week, once every 2 d during the second week, and once a week during the remaining time. Subsamples were analyzed for pH (5 g soil and litter, 12.5 mL water), water content (1 g soil and litter dried at 105°C for 24 h), and inorganic N (5 g soil and litter with 40 mL 1 M KCl) at 0, 1, 4, 7, 14, 28, 56, 82, and 112 d. No additional water was added to the samples during incubation. The average initial soil water content was 0.108 g H2O g-1 (-0.02 MPa) and the average final water content after 112 d was 0.082 g H2O g-1 (-0.07 Mpa).

Near Infrared Reflectance Spectroscopy Measurements
Freeze-dried litter was ground with a Cyclotec mill (Tecator [Hoganus, Sweden] 1093 Sample Mill) and 2-g samples were packed in sample cells of a NIRSystems (Silver Spring, MD) 6500 Monochromator. Near infrared reflectance measurements were made from 780 to 2500 nm in 2-nm intervals. The 99 broiler litter samples were scanned 16 times, and the data were averaged and transformed to log (1/R), where R is reflectance. Due to limitations in incubator space, a subset of 60 litter samples with different spectral characteristics was selected for this study. The program NIRS3 V.4.01 (NIRSystems) was used to select 60 litter samples (out of 99) that provided a large variability in the number and magnitude of spectral peaks. The spectral analysis consisted of taking the first derivative of log (1/R) every four data points (8 nm) in the band ranging from 780 to 2500 nm. The NIRS3 program was also used to process the data and develop the regression model for PMN. The program used a modified partial least square procedure to analyze the reflectance data (Næs and Irgens, 1986) using the wavelength bands as independent variables and PMN as the dependent variable. In addition, NIRS3 used cross validation, which allows one set of samples to act as both calibration and validation set (Osborne et al., 1993), to develop the equation to predict PMN from NIRS measurements.

Water-Soluble Organic Nitrogen
Water-soluble N was measured by extracting 0.6 g of freeze-dried litter with 100 mL deionized water for 30 min, digesting the extract with an alkaline persulfate oxidation, and analyzing the extract for NO-3–N (Cabrera and Beare, 1993). The WSON was calculated by subtracting inorganic N (NH4 + NO2 + NO3) from water-soluble N.

Statistical Methods
Cumulative net N mineralized at each extraction time was calculated from the equation:

where Nm is mineralized nitrogen and Ni is inorganic nitrogen at each extraction time.

Procedure NLIN in SAS (SAS Institute, 1994) was used to fit the data to a one-pool, first-order kinetics model of the form Nmt = PMN , where Nmt is cumulative nitrogen mineralized in time t, PMN is potentially mineralizable nitrogen, and k is the rate constant of mineralization in days. Linear regression analysis was used to relate the measured PMN values with WSON measurements and with PMN values predicted by NIRS.


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
SUMMARY AND CONCLUSIONS
 REFERENCES
 
Litter Characteristics
The broiler litters used in the study varied widely in their composition, as indicated by total N concentrations ranging from 23.8 to 47.0 g N kg-1, total C concentrations varying from 245.3 to 429.8 g C kg-1, and inorganic N concentrations ranging from 1.38 to 13.4 g N kg-1 (Table 1). It is possible that freeze-drying of the samples may have caused losses of inorganic N as ammonia, as found by Van Kessel et al. (1999) for dairy slurries. Ash content in our samples ranged from 126.1 to 416.0 g kg-1 (mean = 214.9 g kg-1) and pH varied from 7.2 to 8.4 (mean = 7.8; Table 1).


View this table:
[in this window]
[in a new window]
  		Table 1. Litter pH, potentially mineralizable nitrogen (PMN) determined by aerobic incubation, inorganic N, water-soluble organic nitrogen (WSON), total N, and total C in 60 broiler litter samples (means of two replications, dry weight basis)

 
Potentially Mineralizable Nitrogen
The pattern of N mineralization from broiler litter was similar to that reported by Gordillo and Cabrera (1997). In all cases there was an initial, fast release of N followed by a slower rate of mineralization (data not shown). The PMN in broiler litter ranged from 6.2 to 27.8 g kg-1 with a mean of 16.6 g kg-1 (Table 1). Expressed as a percentage of the organic N present in the litter, PMN varied from 24.5 to 78.6% (mean = 52.5%). These values are within the range of those reported by Bitzer and Sims (1988), Serna and Pomares (1991), and Gordillo and Cabrera (1997). It should be kept in mind, however, that our samples were sieved through a 2-mm screen and freeze-dried. Previous work by Ndegwa et al. (1991) showed an increase in total N in the smaller size fractions of poultry litter. Also, freeze-drying could have affected the organic fraction of broiler litter, making it more susceptible to mineralization (Van Kessel et al., 1999). It is for this reason that the samples used for incubation were also sieved and freeze-dried, so that the results obtained with NIRS and WSON analysis could be related to incubation results.

Near Infrared Reflectance Spectroscopy Measurements
Unique spectral wavelengths were found in the 1200 to 2400 nm range that were strongly related to PMN (Fig. 1) . These features are attributed to water (OH bond at 1416 and 1900 nm), proteins (NH bond at 1220 and 2072 nm), and lipids (CH bond at 1736, 1770, 2318, and 2356 nm) (Osborne et al., 1993). The calibration equation obtained for PMN had an R2 value of 0.82 (Fig. 2) and a slope of 1.0, with a standard error of cross validation of 2.01 g N kg-1 litter (CV = 12.06%). These results indicate that it is possible to use NIRS to obtain reasonable estimates of PMN in broiler litter.



View larger version (23K):
[in this window]
[in a new window]
  		Fig. 1. First derivative of log (1/R) versus wavelength for a typical broiler litter sample

 


View larger version (20K):
[in this window]
[in a new window]
  		Fig. 2. Regression analysis of measured potentially mineralizable nitrogen (PMN) values in broiler litter versus near infrared reflectance spectroscopy (NIRS)–predicted PMN values

 
One drawback of NIRS is that it requires a NIR scanner, which is an expensive instrument not available in every routine service laboratory. Another possible drawback of NIRS is that it is necessary to dry the samples before analysis because water can affect the results. Depending on the method used, drying can take from 1 (convection oven) to 5 d (freeze drier). In addition to drying, it is necessary to grind the samples because differences in packing can lead to differences in NIRS results; grinding homogenizes the sample and facilitates consistent packing. Because of all the processing required, NIRS has a continual need for calibration and quality control, which can be a major disadvantage. Taking this processing into consideration, the NIRS method can have a sample turnaround time ranging from 2 to 7 d.

Water-Soluble Organic Nitrogen
We selected WSON as a variable of interest because we reasoned that organic N soluble in water may be easier to mineralize than the remainder of the organic N present in broiler litter. Limited data collected by Gordillo and Cabrera (1997) had provided evidence that this may be the case for broiler litter. In this study, WSON ranged from 5.8 to 20.4 g N kg-1, a range not very different from that observed for PMN (6.2 to 27.8 g N kg-1). When we regressed PMN against WSON, we obtained an R2 = 0.87, indicating that WSON can be a useful tool for estimating PMN in broiler litter (Fig. 3) . The intercept of the regression equation (-0.018) was not significantly different from zero but the slope (1.29) was significantly different from 1 (p < 0.05). This suggested that PMN in broiler litter includes an amount of water-insoluble organic N equivalent to 30% of the WSON.



View larger version (19K):
[in this window]
[in a new window]
  		Fig. 3. Regression analysis of potentially mineralizable nitrogen (PMN) in broiler litter versus water-soluble organic nitrogen (WSON). RMSE = root mean square error

 
The measurement of WSON requires extraction, digestion, and measurement of the soluble organic N. This could take 1 to 2 d in a routine service laboratory. After adding the drying and grinding time, the overall sample turnaround time would be 2 to 7 d, as with the NIRS method. The turnaround time for WSON measurement could be decreased if determinations were made with fresh, unground broiler litter samples, but in that case it would be necessary to use large sample sizes (>20 g) to account for the heterogeneity commonly found in broiler litter. The instrumentation required for WSON measurement is a block digestor and a spectrophotometer (manual or automated) for inorganic N determinations, both of which are commonly found in routine service laboratories.


   SUMMARY AND CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 SUMMARY AND CONCLUSIONS
REFERENCES
 
The objectives of this study were to evaluate NIRS and WSON as tools to estimate PMN in broiler litter. We found strong relationships between measured- and NIRS-predicted PMN , and between measured PMN and WSON . These results indicate that both tools may be useful to estimate PMN in broiler litter. Although the sample turnaround time is similar for both methods, WSON may be the easiest method to adopt because it requires less expensive instrumentation and may not need continual calibration, as may be the case for NIRS. It should be kept in mind, however, that these results were obtained with samples that were sieved (2 mm) and freeze-dried. Future work should further test both methods for their ability to estimate mineralizable N in whole, moist broiler litter under field conditions.


   ACKNOWLEDGMENTS
 
We are grateful to John Rema, Andrea Wilbanks, Juli Leonard, and Nicole Wilson for laboratory assistance. We are also grateful to the Fieldale Corporation for their assistance with broiler litter collection.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 SUMMARY AND CONCLUSIONS
 REFERENCES
 




This article has been cited by other articles:


Home page
 Agron. J.Home page
D. A. Ruiz Diaz, J. E. Sawyer, and A. P. Mallarino
Poultry Manure Supply of Potentially Available Nitrogen with Soil Incubation
Agron. J., August 11, 2008; 100(5): 1310 - 1317.
[Abstract] [Full Text] [PDF]

Home page
 J. Environ. Qual.Home page
D. M. Crohn
Optimizing Organic Fertilizer Applications under Steady-State Conditions.
J. Environ. Qual., March 1, 2006; 35(2): 658 - 669.
[Abstract] [Full Text] [PDF]

Home page
 Soil Sci.Home page
S. Agehara and D. D. Warncke
Soil Moisture and Temperature Effects on Nitrogen Release from Organic Nitrogen Sources
Soil Sci. Soc. Am. J., September 29, 2005; 69(6): 1844 - 1855.
[Abstract] [Full Text] [PDF]

Home page
 J. Environ. Qual.Home page
J. Beraud, P. Fine, U. Yermiyahu, M. Keinan, R. Rosenberg, A. Hadas, and A. Bar-Tal
Modeling Carbon and Nitrogen Transformations for Adjustment of Compost Application with Nitrogen Uptake by Wheat
J. Environ. Qual., March 1, 2005; 34(2): 664 - 675.
[Abstract] [Full Text] [PDF]

Home page
 J. Environ. Qual.Home page
G. M. Pierzynski and K. A. Gehl
Plant Nutrient Issues for Sustainable Land Application
J. Environ. Qual., January 1, 2005; 34(1): 18 - 28.
[Abstract] [Full Text] [PDF]

Home page
 J. Environ. Qual.Home page
M. L. Cabrera, D. E. Kissel, and M. F. Vigil
Nitrogen Mineralization from Organic Residues: Research Opportunities
J. Environ. Qual., January 1, 2005; 34(1): 75 - 79.
[Abstract] [Full Text] [PDF]

Home page
 J. Environ. Qual.Home page
T. A. Hanselman, D. A. Graetz, and T. A. Obreza
A Comparison of In Situ Methods for Measuring Net Nitrogen Mineralization Rates of Organic Soil Amendments
J. Environ. Qual., May 1, 2004; 33(3): 1098 - 1105.
[Abstract] [Full Text] [PDF]

Home page
 J. Environ. Qual.Home page
G. R. Munoz, K. A. Kelling, J. M. Powell, and P. E. Speth
Comparison of Estimates of First-Year Dairy Manure Nitrogen Availability or Recovery Using Nitrogen-15 and Other Techniques
J. Environ. Qual., March 1, 2004; 33(2): 719 - 727.
[Abstract] [Full Text] [PDF]

Home page
 J. Environ. Qual.Home page
J. T. Gilmour, M. A. Koehler, M. L. Cabrera, L. Szajdak, and P. A. Moore Jr.
Alum Treatment of Poultry Litter: Decomposition and Nitrogen Dynamics
J. Environ. Qual., January 1, 2004; 33(1): 402 - 405.
[Abstract] [Full Text] [PDF]

Home page
 Agron. J.Home page
K. D. Shepherd, C. A. Palm, C. N. Gachengo, and B. Vanlauwe
Rapid Characterization of Organic Resource Quality for Soil and Livestock Management in Tropical Agroecosystems Using Near-Infrared Spectroscopy
Agron. J., September 1, 2003; 95(5): 1314 - 1322.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (16)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Qafoku, O.S.
Right arrow Articles by Hill, N.S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Qafoku, O.S.
Right arrow Articles by Hill, N.S.
Agricola
Right arrow Articles by Qafoku, O.S.
Right arrow Articles by Hill, N.S.
Related Collections
Right arrow Animal Waste
Right arrow Nutrient Cycling
Right arrow Water Pollution

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
The SCI Journals Agronomy Journal Crop Science
Journal of Natural Resources
and Life Sciences Education		 Vadose Zone Journal
Soil Science Society of America Journal Journal of Plant Registrations The Plant Genome