Ammonia emission measurements of an intensively grazed pasture

Abstract

Abstract. The quantification of ammonia (NH3) emissions is still a challenge and the corresponding emission factor for grazed pastures is uncertain. This study presents NH3 emission measurements of two pasture systems in western Switzerland over the entire grazing season 2016. During the measurement campaign, each pasture system was grazed by 12 dairy cows in an intensive rotational management. The cow herds on the two pastures differed in the energy to protein balance of the diet. NH3 concentrations were measured upwind and downwind of a grazed subplot with line-integrating open path instruments that were able to retrieve small horizontal concentration differences (< 0.2 µg NH3 m−3). The NH3 emission fluxes were calculated by applying a backward Lagrangian stochastic (bLS) dispersion model to the difference of paired concentration measurements and ranged from 0 to 2.5 µg N–NH3 m−2 s−1. The fluxes increased steadily during a grazing interval from previous non-significant values to reach maximum emissions at the end of the grazing interval. Afterwards they decreased exponentially to near zero-values within 3–5 days. A default emission curve was calculated for each of the two systems and adopted to each rotation in order to account for missing data values and to estimate inflow disturbances due to grazing on upwind paddocks. Dung and cow location were monitored to account for the non-negligible inhomogeneity of cow excreta on the pasture. The average emission (± SD of individual rotation values) per grazing hour was calculated as 0.64±0.11 g N–NH3 cow−1 h−1 for the herd with the N-balanced diet (system M) and 1.07±0.06 g N–NH3 cow−1 h−1 for the herd with the protein-rich grass-only diet (system G). Surveys of feed intake, body weight and milk yield of the cow herds were used to estimate the nitrogen (N) excretion by an animal N budget model. Based on that, mean relative emission factors of 6.4±2.0 % and 8.7±2.7 % of the applied urine N were found for the systems M and G, respectively. The results can be used to validate the Swiss national emission inventory and demonstrate the positive effect of an N-balanced diet on pasture NH3 emissions.

New Emission Factors for Calculation of Ammonia Volatilization From European Livestock Manure Management Systems

“…Ammonia emission from cattle on grassland is highly variable and most of the emission originates from urine patches (Laubach et al, 2012(Laubach et al, , 2013Nichols et al, 2018). Increasing addition of N in fertilizer to the grassland will cause an increase in NH 3 emission due to increased grass N production, greater intake of N and increasing N excretion of which most ends up in the urine (Jarvis et al, 1989;Bussink, 1992;Voglmeier et al, 2018). Ammonia emissions increase with increasing soil moisture content (Bussink, 1992), and air temperature, wind speed, global radiation, and rainfall all influence emissions (Bell et al, 2017;Voglmeier et al, 2018).…”

“…Increasing addition of N in fertilizer to the grassland will cause an increase in NH 3 emission due to increased grass N production, greater intake of N and increasing N excretion of which most ends up in the urine (Jarvis et al, 1989;Bussink, 1992;Voglmeier et al, 2018). Ammonia emissions increase with increasing soil moisture content (Bussink, 1992), and air temperature, wind speed, global radiation, and rainfall all influence emissions (Bell et al, 2017;Voglmeier et al, 2018). The same pattern is seen when studying NH 3 emission from sows on grassland, which was related to the amount of feed given to the sows, incident solar radiation, air temperature and rain (Sommer and Hutchings, 2001).…”

Grazing-related nitrous oxide emissions: from patch scale to field scale

“…Data availability. Data obtained in this study are available online at https://doi.org/10.5281/zenodo.2601821 (Voglmeier et al, 2019).…”

Precise multispecies agricultural gas flux determined using broadband open-path dual-comb spectroscopy

“…The large dependence of NH 3 volatilization on environmental parameters stresses the importance of extended continuous field measurements such as those provided by calibration-free open-path DCS. For example, our results on the wind dependence of NH 3 emission rate will inform future studies aimed at reducing NH 3 emissions using modern management practices such as restricted grazing ( 46 ), targeted manure application ( 47 ), and agricultural windbreaks ( 48 ).…”