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Dynamic Behavior of pH in Fresh Urine Puddles of Dairy Cows

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASABE. 59(5): 1403-1411. (doi: 10.13031/trans.59.11750) @2016
Authors:   Dennis J. W. Snoek, Nico W. M. Ogink, Johannes D. Stigter, Sido Agricola, Teun M. Van de Weijer, Peter W. G. Groot Koerkamp
Keywords:   Ammonia emission, Cow barn, Cow urine, Fresh puddle, pH.

Abstract. Modern livestock farming is an important contributor to ammonia (NH3) emissions. In the Netherlands, 94% of NH3 emissions originate from agriculture, of which 34% is emitted from commercial dairy cow barns. From current mechanistic modeling, it is known that the pH of urine puddles from cows is one of the most important variables in estimating NH3 emissions. However, little pH data are available from commercial cow barns. Therefore, the objective of this study was to investigate pH values and to study their dynamic behavior in fresh, on-floor urine puddles in these barns. To do this, the pH of urine puddles was measured for 4 h per puddle, and a model was developed to describe the pH behavior. In total, 26 fresh puddles were measured from cows at three commercial dairy farms in summer and winter. At farm level, we found initial pH values of 8.1 through 8.4, which increased to 8.9 through 9.4 after 4 h. The pH difference between summer and winter was 0.3 (p < 0.05), but this was not confirmed by comparisons at farm level. The pH curves of individual puddles varied substantially and could be fitted by a nonlinear regression model. This model contained correlated coefficients that were able to describe the main, known chemical processes of a urine puddle. However, no linear relationship was found between initial and final pH and thus between coefficients. On average, pH quickly increased initially, declined after 1 h, and became stable around a pH of 9.15. We conclude that a pH curve will better describe the input variable in NH3 emission modeling than the current situation of using a static pH value. Based on this study, we recommend using the mean measured pH curve as input for puddle simulation during NH3 emission modeling of dairy cow barns.

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