Nitrogen Losses from Dairy Manure Estimated Through Nitrogen Mass Balance and Chemical Markers

Abstract

Ammonia is an important air and water pollutant, but the spatial variation in its concentrations presents technical difficulties in accurate determination of ammonia emissions from animal feeding operations. The objectives of this study were to investigate the relationship between ammonia volatilization and delta15N of dairy manure and the feasibility of estimating ammonia losses from a dairy facility using chemical markers. In Exp. 1, the N/P ratio in manure decreased by 30% in 14 d as cumulative ammonia losses increased exponentially. Delta 15N of manure increased throughout the course of the experiment and delta15N of emitted ammonia increased (p<0.001) quadratically from -31 per thousand to -15 per thousand. The relationship between cumulative ammonia losses and delta15N of manure was highly significant (p<0.001; r2=0.76). In Exp. 2, using a mass balance approach, approximately half of the N excreted by dairy cows (Bos taurus) could not be accounted for in 24 h. Using N/P and N/K ratios in fresh and 24-h manure, an estimated 0.55 and 0.34 (respectively) of the N excreted with feces and urine could not be accounted for. This study demonstrated that chemical markers (P, K) can be successfully used to estimate ammonia losses from cattle manure. The relationship between manure delta15N and cumulative ammonia loss may also be useful for estimating ammonia losses. Although promising, the latter approach needs to be further studied and verified in various experimental conditions and in the field.

Nitrogen Isotope Fractionation and Origin of Ammonia Nitrogen Volatilized from Cattle Manure in Simulated Storage

“…We first reported a significant N isotope fractionation in cattle manure during storage due to NH 3 -N volatilization [4,22]. The isotope fractionation factor associated with NH 3 -N volatilization is one of the highest in the N cycle (~1.029, [23]), which would result, when conditions are favorable, in a rapid increase in …”

“…In each experiment, 3 incubation vessels were used (n = 3). The incubations were carried out for 20 NH 4 Cl were dosed intraruminally to each cow for 5 consecutive days. The isotope was dissolved in 1 L distilled water and dosed twice daily (2 g at each dosing), immediately before the morning and afternoon feedings.…”

“…Emissions of N 2 from cattle manure may be also high, particularly during the initial stage of manure storage when the bulk of urinary N is volatilized. If this is the case, mass balance, or other indirect approaches (i.e., not measuring NH 3 emissions directly; isotope, manure minerals:N ratios [4]) for estimating NH 3 emissions may not be accounting for gaseous non-NH 3 -N losses and thus, NH 3 emissions from cattle operations may be overestimated. For example, 25 and almost 50% of the daily N flow in dairy and beef cattle operations, respectively, were unaccounted as milk, daily body weight gain, or manure [2].…”

“…With such large variability, determining the specific effect of diet is practically impossible. Therefore, we have investigated indirect methods for estimating manure NH 3 emissions, utilizing minerals:N ratios and natural N isotope fractionation [4]. The isotope method appeared promising, however, the relationship between …”

“…The process has been discussed in length [4]. Experiments 1 and 2 were used to determine N isotope ratios beyond the short incubation time utilized in our original studies [4,22].…”