Titration and Spectroscopic Measurements of Poultry Litter pH Buffering Capacity

Abstract

The pH value of poultry litter is affected by nitrification, mineralization, and the addition of acidifying chemicals, all acting on the poultry litter pH buffering capacity (pHBC). Increased understanding of poultry litter pHBC will aid in modeling NH volatilization from surface-applied poultry litter as well as estimating rates of alum applications. Our objectives were to (i) determine the pHBC of a wide range of poultry litters; (ii) assess the accuracy of near-infrared reflectance spectroscopy (NIRS) for determining poultry litter pHBC; and (iii) demonstrate the use of poultry litter pHBC to increase the accuracy of alum additions. Litter pHBC was determined by titration and calculated from linear and sigmoidal curves. For the 37 litters measured, linear pHBC ranged from 187 to 537 mmol (pH unit) kg dry litter. The linear and sigmoidal curves provided accurate predictions of pHBC, with most > 0.90. Results from NIRS analysis showed that the linear pHBC expressed on an "as is" water content basis had a NIRS coefficient of calibration (developed using a modified partial least squares procedure) of 0.90 for the 37 poultry litters measured. Using the litter pHBC, an empirical model was derived to determine the amount of alum needed to create a target pH. The model performed well in the range of pH 6.5 to 7.5 (RMSE = 0.07) but underpredicted the amount of alum needed to reach pH <6. The lack of model performance at pH <6 was probably due to Al reacting with organic matter in the poultry litter, which prevented its hydrolysis.

Urea Hydrolysis and Calcium Carbonate Precipitation in Gypsum‐Amended Broiler Litter

“…The initial amount of HCO 3 − in litter was determined using procedures similar to those of Bundy and Bremner (1972). The litter pH buffering capacity was determined using a titrimetric method described by Cassity‐Duffey et al (2015). There were four replicates used to determine the initial amount of HCO 3 − in broiler litter, and each experimental unit consisted of 10 g of broiler litter (0.33 g H 2 O g −1 ) placed in a 250‐mL Erlenmeyer flask with 200 mL of dH 2 O.…”

Dynamics of Different Buffer Systems in Slurries Based on Time and Temperature of Storage and Their Visualization by a New Mathematical Tool

“…In a study to determine the pH buffer capacity in poultry litter, the titration curve was represented by a linear equation and a sigmoidal curve. After forming the reciprocal of the slope, the sigmoidal curve allowed to plot the pH buffer capacity as a function of pH in the range from 6.5 to 9.5 [38].…”