Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2005
Publication Date: November 1, 2005
Citation: Aiken, G.E., Pote, D.H., Tabler, S.F., Tabler, T.C. 2005. Application of near infrared reflectance spectroscopy to estimate chemical constituents in broiler litter. Communications in Soil Science and Plant Analysis. 36:2529-2539. Interpretive Summary: Litter that is produced as a byproduct from confined poultry production has been extensively utilized as an organic fertilizer for grazed pastures and hay meadows. Broiler litter has provided an economical alternative to costlier commercial fertilizer, but mineral imbalances with the organic fertilizer has caused some environmental concern. Producers typically set application rates of broiler litter that are based on plant requirements for nitrogen, but the nitrogen content of litter is low relative to phosphorus. Consequently, phosphorus can accumulate in soils and increase phosphorus in runoff to levels that can eventually pollute surface waters. Producers should therefore restrict application rates to those that meet plant requirements for phosphorus. Accurate knowledge of the P content of a litter source will therefore be necessary; however, chemical analyses of manure fertilizers are too costly and time consuming to be practical. An experiment was conducted to determine if near infrared reflectance spectroscopy could be used as a rapid indirect method to accurately determine nitrogen and phosphorus concentrations in broiler litter. Equations derived with the technology estimated the two constituents, but accuracy was too low to provide reliable estimates. The technology has potential to provide rapid estimates of broiler litter composition, but improved methodologies are needed to enhance accuracy.
Technical Abstract: Near infra-red reflectance spectroscopy (NIRS) has potential to provide rapid estimates of phosphorous (P) and nitrogen (N) concentrations in broiler litter to assist managers in establishing application rates of litter to grazing lands that fall within productive and environmentally safe levels. An experiment was conducted to determine accuracy of NIRS estimates of moisture, P, N, and acid detergent fiber concentrations in bedding material. Broiler litter samples were collected from various farms to develop sample sets that were either with or without bedding material and each sample set was subdivided into processed (i.e. dried and ground) and unprocessed samples to develop local equations for each constituent. Equations were developed using all samples from each set and using samples following random removal of 20% of total for equation validation. Moisture was determined to be accurately measured using NIRS based on with high coefficient of variation (?0.96), low standard error of calibration (< 10 g/kg), and high ratio between standard deviation for reference measures and standard error of cross-validation (s.d./SECV) (> 5.0). Acid detergent fiber also had a high coefficient of determination (0.96), but the s.d./SEC (3.00) value was too low for the equation to be considered truly accurate. Estimations of P and N by calibrations that included all samples had a moderate to high coefficient of determination values, but estimations for the validation set were relatively low in coefficients of determination (0.78) and s.d/SEC (2.00). Concentrations of P and N were not estimated by NIRS with a high degree of accuracy but other methodologies could enhance the usefulness of this technology to rapidly provide these nutrient measures.