A rapid method for determining TN and TP concentrations in swine slurry using historical data

S. F. Higgins, S. A. Shearer, M. S. Coyne, J. P. Fulton

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Quantifying nitrogen and phosphorus concentrations in liquid swine manure at the time of field application offers potential benefits that include reduced environmental impact from over-applying nutrients and better matching of manure nutrient levels with fertilizer recommendations or crop removal rates. This study developed and assessed a rapid on-farm method to predict total nitrogen (TN) and total phosphorus (TP) concentrations of swine slurries for a single farm. Swine slurry samples were collected from gestating sow and finishing barn deep pits during loading. A liquid ratio (liquid volume/filtrate volume) was generated by sieving a known manure volume through a 0.85 mm sieve. Gestation and finishing barn liquid ratios correlated well with total solids (TS) (R 2 = 0.89). Regression analysis demonstrated that the liquid ratio and historical TN and TP concentrations of manure sample results could be used to predict TN and TP concentrations (R2 = 0.92) prior to field application. Liquid ratio explained 82% of the TP variance, while a proxy variable for swine growth stage explained an additional 10% of the TP variance. The proxy variable relating to swine growth stage explained 89% of the TN variance, whereas adding the liquid ratio explained an additional 2% of the variance. Model predictions of TN and TP concentrations for finishing barn validation samples exhibited mean prediction errors of 11% and 10%. Gestation barn predictions indicated that the models were precise, but not accurate, with an average error of 61% for TN and 48% for TP; these errors were attributed to retaining slurry for an additional season. This study showed that liquid ratio can be used as a rapid method for predicting TP concentrations of swine slurries, whereas animal growth stage is a better predictor of TN.

Original languageEnglish
Pages (from-to)1727-1737
Number of pages11
JournalTransactions of the ASABE
Issue number5
StatePublished - Sep 2004


  • Environment
  • Manure application
  • Nutrients
  • Precision agriculture
  • Site-specific

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)


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