Livestock watering can represent as much as 20% of total agricultural water use in areas with intensive dairy farming. Due to an increased emphasis on water conservation for the agricultural sector, it is important to understand the current patterns of on-farm water use. This study utilized in situ water meters to measure the year-round on-farm pumped water (i.e., blue water) on a~419 lactating cow confined dairy operation in Eastern Ontario, Canada. The average total water use for the farm was 90,253 ± 15,203 L day −1 and 33,032 m 3 annually. Water use was divided into nutritional water (68%), parlour cleaning and operation (14%), milk pre-cooling (15%), barn cleaning, misters and other uses (3%). There was a positive correlation between total monthly water consumption (i.e., nutritional water) and average monthly temperature for lactating cows, heifers, and calves (R 2 = 0.69, 0.84, and 0.85, respectively). The blue water footprint scaled by milk production was 6.19 L kg −1 milk or 6.41 L kg −1 fat-and-protein corrected milk (FPCM) including contributions from all animal groups and 5.34 L kg −1 milk (5.54 L kg −1 FPCM) when excluding the water consumption of non-lactating animals. By applying theoretical water conservation scenarios we show that a combination of strategies (air temperature reduction, complete recycling of milk-cooling water, and modified cow preparation protocol) could achieve a savings of 6229 m 3 annually, a~19% reduction in the total annual water use.

Current approaches for estimating greenhouse gas (GHG) emissions from manure storages do not consider contributions due to bedding materials. Compared with sand, wood-based bedding has the potential to increase volatile solids and total solids concentrations and favour crust formation in liquid dairy manure. In this study, the GHG emissions from wood and sand bedding slurries were evaluated monitored continuously for 207 d (1 May-24 Nov. 2014) under "warm season" storage conditions. For both slurries, methane (CH 4 ) made up >95% of the GHG emissions. The sand bedding slurry had minimal crust, which also led to more evaporation and higher ammonia volatilization losses when scaled by nitrogen content. The wood bedding slurry emitted 51% more CH 4 , eight times more nitrous oxide, and 53% more total GHG emissions (CO 2 -eqivalents). However, these differences were reduced if only the initial 123 d (1 May-31 Aug. 2014) of storage was considered. This was presumably related to the slower degradability of the wood bedding. Given these differences bedding choice should be considered in GHG emissions estimates.Résumé : Les approches actuelles employées pour estimer le volume de gaz à effet de serre (GES) que dégagent les réserves de fumier ne tiennent pas compte des émissions issues de la litière. Contrairement au sable, les copeaux de bois peuvent augmenter la concentration de solides volatils (SV) et de solides totaux. Ils favorisent aussi la formation d'une croûte à la surface du lisier des bovins laitiers. Les auteurs ont évalué les émissions de GES des boues de litière ligneuse et sableuse de façon continue pendant 207 jours (du 1 er mai au 24 novembre 2014), soit dans les conditions de stockage de la « belle saison ». Le méthane (CH 4 ) représente plus de 95 % des GES libérés par les deux types de boues. La boue de litière sableuse ne présentait qu'une très mince croûte, si bien que l'évaporation et la volatilisation de l'ammoniac étaient plus importantes, proportionnellement à la quantité d'azote. La boue de litière ligneuse a libéré 51 % de CH 4 de plus, huit fois plus d'oxyde nitreux et 53 % de plus de GES au total (en équivalent de CO 2 ). Toutefois, ces écarts s'atténuent quand on ne tient compte que des 123 premiers jours de stockage (du 1 er mai au 31 août 2014), sans doute à cause de la dégradation plus lente des copeaux de bois. Face à de telles variations, l'estimation des émissions de GES devrait prendre en compte la nature de la litière employée. [Traduit par la Rédaction] Mots-clés : fumier, émissions de gaz à effet de serre, méthane, oxyde nitreux, ammoniac, bovins laitiers.

A significant need exists to improve our understanding of the extent of greenhouse gas emissions from the storage of livestock manure to both improve the reliability of inventory assessments and the impact of beneficial management practice adoption. Factors affecting the extent and variability of greenhouse gas emissions from stored dairy manure were investigated. Emissions from six slurries stored in clean concrete tanks under identical "warm-season" conditions were monitored consecutively over 173 d (18°C average air temperature). Methane (CH) emissions varied considerably among the manures from 6.3 to 25.9 g m d and accounted for ∼96% of the total CO equivalent greenhouse gas emissions. The duration of the lag period, when methane emissions were near baseline levels, varied from 30 to 90 d from the beginning of storage. As a result, CH emissions were poorly correlated with air temperature prior to the time of peak emissions (i.e., the initial 48 to 108 d of storage) but improved afterward. The air temperature following the time of the peak CH flux and the length of the active methanogenesis period (i.e., when the daily CH emissions ≥ 7.6 g m d) were highly correlated with CH emissions ( = 0.98, < 0.01). Methane conversion factors (MCFs) ranged from 0.08 to 0.52 for the different manures. The MCFs generated from existing CH emission models were correlated ( = 0.68, = 0.02) to MCFs calculated for the active methanogenesis period for manure containing wood bedding. A temperature component was added that improved the accuracy ( = 0.82, < 0.01). This demonstrated that an improved understanding of lag period dynamics will enhance stored dairy manure greenhouse gas emission inventory calculations.

Liquid manure storages are a significant source of methane (CH 4 ) emissions. Farmers commonly agitate (stir) liquid manure prior to field application to homogenize nutrients and solids. During agitation, manure undergoes mechanical stress and is exposed to the air, disrupting anaerobic conditions. This on-farm study aimed to better understand the effects of agitation on CH 4 emissions, and explore the potential for intentional agitation (three times) to disrupt the exponential increase of CH 4 emissions in spring and summer. Results showed that agitation substantially increased manure temperature in the study year compared to the previous year, particularly at upper-and mid-depths of the stored manure. The temporal pattern of CH 4 emissions was altered by reduced emissions over the subsequent week, followed by an increase during the second week. Microbial analysis indicated that the activity of archaea and methanogens increased after each agitation event, but there was little change in the populations of methanogens, archaea, and bacteria. Overall, CH 4 emissions were higher than any of the previous three years, likely due to warmer manure temperatures that were higher than the previous years (despite similar air temperatures). Therefore, intermittent manure agitation with the frequency, duration, and intensity used in this study is not recommended as a CH 4 emission mitigation practice.Implications: The potential to mitigate methane emissions from liquid manure storages by strategically timed agitation was evaluated in a detailed farm-scale study. Agitation was conducted with readily-available farm equipment, and targeted at the early summer to disrupt methanogenic communities when CH 4 emissions increase exponentially. Methane emissions were reduced for about one week after agitation. However, agitation led to increased manure temperature, and was associated with increased activity of methanogens. Overall, agitation was associated with similar or higher methane emissions. Therefore, agitation is not recommended as a mitigation strategy.