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When liquid manure is removed from storages for land application, "sludge" generally remains at the bottom of the tank. This may serve as an inoculum when fresh manure is subsequently added, thereby increasing methane (CH) emissions. Previous pilot-scale studies have shown that completely emptying storages can decrease CH emissions; however, no farm-scale studies have been conducted to quantify the effect of sludge removal. In this study, a commercial dairy farm removed as much manure and sludge from their concrete storage as possible in the fall (∼2% by volume remained). Emissions of CH were measured during the following winter, spring, and summer, and compared with emissions measured the preceding 2 yr when most of the sludge had not been removed (∼14% of tank volume remained). Emissions were measured using a micrometeorological technique, utilizing open-path CH lasers. Contrary to what was hypothesized, removing the majority of sludge in fall did not delay the onset of CH emissions and did not decrease emissions the following summer. In fact, annual CH emissions were ∼16% higher. It is possible that fall removal provided sufficient time for microbial dynamics to be restored before the following summer when emissions were high. Future farm-scale research should examine the effect of spring (rather than fall) emptying for on-farm CH mitigation in both concrete tanks and earthen storages.

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.