Manure is an important resource of carbon and nutrients, especially nitrogen and phosphorous, for soils. However, using manure effectively is beset with technical and logistical challenges. This chapter discusses the many of these issues and advances in using dairy manure, especially slurry, to replace commercial fertilizers and improve soils. The chapter deals with problems of preserving nutrients and providing the best crop response and carbon balance, with minimal impact on farms and their surroundings. The advances in using dairy slurry employ short and long term field studies, integrated farm management systems, and farmer based approaches. Directions for further improvements in using dairy manure are identified.

Information about soil organic matter fraction and enzyme activity responses to agricultural management may help guide decisions that sustain crop productivity and soil health. We measured carbon and nitrogen in bulk soil, mineral-associated organic matter, particulate organic matter, water-extractable organic matter, and the potential activity of β-glucosidase, N-acetyl-β-d-glucosaminadase, acid phosphomonoesterase and arylsulfatase in three cropping systems after: 1) 21-years of conventional- or no-tillage silage corn monoculture (0-20-cm); and 2) six years of nitrogen fertilization with or without nitrification inhibitors and 3) nine years of 100 or 200% the recommended broadcast or fertigation nitrogen rate in two distinct mature highbush blueberry systems (0-15-cm). Soil organic carbon, particulate organic carbon, particulate organic nitrogen, water-extractable nitrogen and arylsulfatase activity were 17%, 38%, 50%, 25% and 68% greater, respectively, with no-tillage than conventional tillage. Particulate organic carbon accumulated with two decades of no-tillage, which increased soil organic carbon without altering mineral-associated organic carbon. Nitrification inhibitors did not impact any soil organic matter fraction or enzyme activity after six years in a mature highbush blueberry system. Broadcasted nitrogen led to higher soil organic carbon than fertigation, but excessive application (200% vs 100% rate) depleted soil organic carbon, accumulated reactive nitrogen and reduced potential activity of N-acetyl-β-d-glucosaminadase, acid phosphomonoesterase and arylsulfatase after nine years in a mature highbush blueberry system. Excessive nitrogen may deplete organic carbon and cause reactive nitrogen accumulation in soil of mature highbush blueberry systems. Intensive agricultural management has trade-offs for carbon and nitrogen cycling that should be balanced with sustainable crop production.

CONTEXT: The dairy sector contributed $19.9 (CAD) billion to Canada's GDP in 2015, but the industry has come under increasing public scrutiny regarding its environmental and economic sustainability, particularly under climate change. The Fraser Valley region of British Columbia, Canada, a high-intensity dairy producing region, is projected to experience higher winter, spring and summer temperatures and increased precipitation, particularly in fall, with implications for nitrogen (N) cycling within agroecosystems, crop and livestock production. OBJECTIVE: This study aimed to explore N flows in a Canadian dairy farm using a whole-farm partially process-based modelling approach to investigate the impacts of different climate and cropping scenarios on farm N inputs and outputs. METHODS: This study used farm data and the Integrated Farm System Model (IFSM) to assess: 1) N flows in an intensive, high-producing dairy farm in the Lower Fraser Valley with and without a winter double crop; and 2) farm production and N losses under two future climate scenarios based on medium (RCP4.5) and high (RCP8.5) emission scenarios in the near future (NF, 2020-2045) and distant future (DF, 2050-2075). RESULTS AND CONCLUSIONS: Across all scenarios, the N use efficiency of the farm (N exported in meat, milk and feed / N inputs) was between 31.4 % and 34.3 % (slightly higher with winter wheat (Triticum aestivum L.)), indicating that about two-thirds of N imported as feed and fertilizer was lost to the environment or accumulated in the soil. In the NF and DF scenarios (without double crop), the largest increases related to manure NH3-N losses, which rose by 8.1 % (NF) and 19.4 % (DF) from housing; 15.7 % (NF) and 44.0 % (DF) from storage; and 3 % (NF) and 18.5 % (DF) following land application. Projected temperature increases also raised emissions from synthetic fertilizer. Other gaseous N emissions generally declined in the future, probably due to increased NH3-N losses, whereas leaching N losses increased slightly (0.5-1.6 %), probably due to higher projected summer and fall precipitation. The winter wheat double crop scenarios generally led to lower N losses via gaseous pathways and leaching/runoff compared with the baseline scenarios, attributable to more N capture by winter wheat. SIGNIFICANCE: The apparent loss to surrounding water and air of at least two-thirds of the N imported to the farm highlights the urgent need for the implementation of a range of management strategies that can reduce overall N imports to the system and reduce losses of N inputs via volatilization, runoff and leaching.

Canada's livestock production and human populations are concentrated in southern regions. Understanding spatial and temporal distributions of animals and excreted nutrients is key to optimizing manure resources and minimizing impact of livestock. Here, we identify manureshed concerns and opportunities by reconciling nitrogen supply and demand on a regional and national scale. Data based on national statistics and farm surveys were allocated to homogeneous soil polygons (Soil Landscapes of Canada [SLC]) to quantify changes in nutrient distribution and ammonia (NH3 ) emissions across Canada (1981-2018). Livestock sectors tied to domestic consumption, dairy and poultry, were stable over time and well dispersed. Export driven beef production has moved west since 1981, whereas pig production was prominent in Manitoba, Quebec, and Ontario. Per ha manure N excretion across livestock sectors in 2018 was generally low with 58% and 6% of the SLCs averaging <25 and >100 kg N ha-1 , respectively. Although only 3% of SLCs had average NH3 emissions reaching 16-200 kg ha-1 , most of these were located near cities and emissions spiked in spring when more people might be exposed. The greatest concentrations of nutrients and livestock occurred around the three largest metropolitan areas: Toronto, Montreal-Quebec City, and Vancouver, posing challenges for nutrient recycling and public health. This study shows that as Canadian cities and livestock agriculture grow in southern Canada, so will challenges around food production, human health, and managing nutrients. Livestock and land use strategies are needed to reconcile changing animal sectors and growing populations.

Alfalfa (Medicago sativa L., AL)-based forage mixtures are a major constituent of ruminant rations, and optimizing their energy-to-protein ratio has been identified as a way to improve N use efficiency. This study aimed to determine whether the energy-to-protein ratio could be improved by adding red clover (Trifolium pratense L., RC) or birdsfoot trefoil (Lotus corniculatus L., BT) at different seeding proportions, and/or one grass species [timothy, Phleum pratense L., or tall fescue, Schedonorus arundinaceus (Schreb.) Dumort] to AL. Annual forage yield, species proportion in botanical composition, and nutritive value of forage were measured at three sites in Canada for 2 post-seeding years. The addition of RC or BT did not affect the annual forage yield but it increased the concentration of forage nonfiber carbohydrates (NFCs), particularly of soluble sugars, and decreased concentrations of crude protein (CP), nonprotein nitrogen (NPN), and rapidly degradable protein (PB1) of AL-based mixtures. The addition of one percentage unit of RC or BT to forage botanical composition improved the NFC/CP ratio by 0.005, and the NFC/(NPN + PB1) ratio by 0.024. The addition of either grass species to AL mixtures also increased the two ratios, but it was related to a CP decrease with no increase in NFC concentrations. Adding RC or BT to AL-based mixtures is therefore a valuable strategy to increase the forage energy to protein ratio.

National inventory reporting of agricultural nitrous oxide (N 2 O) emissions in Canada is based primarily on measurements obtained using static chambers. In regions with cold winters and an accumulated snowpack (including Canada), these measurements tend to focus on the growing season (typically May–October). However, research has shown that emissions continue throughout the non-growing season (NGS) and that these account for a significant proportion of annual emissions. In the Canadian National Inventory NGS emissions currently are assumed to be adequately captured in western Canada, while they are accounted for in eastern Canada by multiplying the growing season emissions by a correction factor of 1.4, a value that was derived based on a limited number of measurements. Here we use recent Canadian studies to validate this correction factor. We collected data from available Canadian studies that measured soil N 2 O emissions from agricultural systems for the entire year and determined the proportion of these emissions that occurred during the NGS. The proportion of annual N 2 O emissions that occurred during the NGS varied widely, ranging from −4% to 119% with a mean of 35.5%, compared to the previous estimate of 30%. Due to high variability, few differences were observed between means associated with climatic, soil, and management variables. To correct for NGS N 2 O emissions from Canadian agricultural soils, we suggest that the current correction factor for converting growing season to total annual emissions be changed from 1.4 to 1.55 and that this be used for all agricultural soils in Canada rather than just eastern Canada.

The objectives were to determine the effects of incrementally applied improved nutrient management, alternative cropping practices, and advanced production technologies in a dual forage system of perennial grass and silage corn on nutrient composition and in vitro ruminal fiber digestibility of the forages and, using these data as inputs into the Cornell Net Carbohydrate and Protein System, to predict milk production, indicators of nitrogen (N) utilization, and N excretion of dairy cattle. Farm management systems (farmlets) included a conventional system with whole manure slurry broadcast to a late maturing corn hybrid and grass harvested with 5 cuts per year (F1); improved nutrient management with a separated manure system where the sludge was applied to corn and the liquid was applied to grass (F2); improved nutrient management and alternative cropping practices with separated manure, an early maturing corn hybrid interseeded with a relay winter cover crop, and grass harvested with 3 cuts per year (F3); and improved nutrient management and alternative cropping practices combined with advanced production technologies that included irrigation and a nitrification inhibitor (F4). The field trial was a randomized complete block design over 2 yr with 4 blocks each divided into grass and corn, 4 subplots within each block for each crop, and 2 replicates within each subplot. Diets were formulation with 60% forage and 40% concentrate where the grass and corn as silage was proportional to yield for land allocations of grass and corn of 80:20, 60:40, 40:60, and 20:80. Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc.). The intensified management systems (F2, F3, and F4) increased the crude protein (CP) concentration of corn with no effects on starch concentration [32.1% dry matter (DM)] compared with the conventional system (F1). Decreasing cuts of grass from 5 to 3 reduced the CP concentration in the spring harvest (15.8% vs. 12.5% DM), and increased fiber concentration and reduced digestibility in the spring, summer, and fall harvests. A common concentrate was formulated for the conventional farmlet and then combined with the forages for each farmlet within each land allocation. Forages grown under intensified management to improve N capture increased the CP concentration of the diets. However, reducing the number of cuts of grass from 5 to 3, combined with the corn and relay crop to increase yield, reduced milk production across all land allocations. To complement the nutritive value of the forages grown under each management system and land allocation, the concentrates were reformulated, which reduced dietary CP, improved the indicators of N utilization (e.g., milk urea N and milk N efficiency), reduced N excretion, and improved milk yield with no differences among the farmlets. Increasing land allocated to corn supported higher milk yield at lower dietary CP concentrations (16.5% vs. 15.4% DM) with improved milk N efficiency and lower N excretion. Intensified agronomic management increased the CP of the combined forages decreasing the need for supplemental CP in the concentrate and could reduce the importation of feed N to the farm.

Animal manure can be a serious environmental concern if improperly managed, particularly with regard to phosphorus (P). A good understanding on manure P chemistry is required for improving manure management in an environmentally sustainable manner. In the study, 102 representative manure samples collected from farms of major intensive livestock areas of Canada were sequentially fractionated with H2O, 0.5 M NaHCO3, 0.1 M NaOH, and 1.0 M HCl, respectively, for measuring inorganic (Pi) and organic P (Po). Across the manures, total P (TP) ranged from 3.71 to 17.3 g kg−1, with total Pi and available P (i.e., the sum of H2O-Pi and NaHCO3-Pi) accounting for 67.0–92.4 % and 35.6–67.3 % of TP, respectively. Composting reduced the percentages of available P and Po in TP, and meanwhile increased the percentages of moderately stable HCl-Pi. Compared to other P fractions, manure available P increased more rapidly with increases in TP; once manure TP reached 7.8–9.6 g kg−1, further TP increase enhanced transformation to more recalcitrant P (i.e., NaOH-Pi and HCl-Pi). Under Canadian conditions, manure application to meet the demand of crops for N would lead to P buildup in the soil at rates of 6.1–41.6 kg P ha−1 yr−1, increasing runoff P loss risk. Manure compost and poultry manure tend to cause rapid P buildup in the soil after land application and become a long-term P source for runoff losses. The results help to develop scientifically-sound manure-specific P management technologies which would enable farmers to achieve sustainable crop production with improved environment.

Livestock production in the United States（US） and Canada is diverse, but shows a common trend in most livestock sectors toward fewer farms producing the majority of animal products despite a large number of farms still small in production scale. The migration to larger and more concentrated animal feeding operations in beef finishing and poultry, swine, and dairy production allows processors to streamline supplies to meet market demand for abundant, lowcost livestock products, whether that be for packaged meat, dairy products, or eggs. With concentration of livestock operations comes the challenge of managing manures. When sufficient land is available and nutrients are needed,livestock manure is an excellent nutrient source and land application is the preferred method of recycling this resource. However, when livestock production is constrained in a geographical area and animal densities are high, manure may become an environmental liability with potentially greater risk for runoff and leaching of nutrients, emission of odors, ammonia, and greenhouse gases, and release to the environment of pathogens and chemicals of emerging concern. Addressing these challenges now and into the future requires learning from mistakes and adopting successful approaches. We describe different levels of integration between livestock and crop producers in New York, British Columbia, and the south-eastern US as learning opportunities to improve economic and environmental sustainability. Examples show that effective solutions should recognize（1） manure has value and is not just a cost,（2） farmers, farm advisors, extension educators, nutrient management planners,crop advisors, nutritionists, state agency personnel, regulators, and university researchers need to be active participants in development of solutions, and（3） change to a sustainable future requires a combination of government regulation and outcome-based incentives.

Starter mineral fertilizer is used by famers to provide phosphorus (P) and nitrogen (N) to emerging corn (Zea mays) plants. Recent studies have shown that dairy slurry can replace mineral fertilizer provided it is precisely positioned close to the corn rows. This 5-year study examined the multi-year effect of precision injected sludge, the thick fraction separated from dairy slurry, on growth and nutrient uptake at the 6-leaf stage and final harvest of no-till corn. The sludge was first injected 15 cm deep and the corn planted < 10 cm from the sludge furrow at least 3 days later. Sludge provided sufficient P for both early growth and full season growth. At final harvest with equivalent total N and P rates (32P 250N treatments), fertilizer and sludge had similar maximum yields (17.9 and 17.4 t ha−1, respectively) and P uptake (26 and 25 kg ha−1, respectively) but fertilizer had higher N uptake than sludge (200 and 162 kg ha−1). N uptake and recovery N use efficiency was greater for sludge than fertilizer based on equivalent min.-N which suggests crop benefits in the sludge other than min-N and P. The study shows that precisely injected dairy sludge can obviate the need for starter mineral fertilizer, and this may help to alleviate P surpluses on dairy farms. This practice also provides a use on dairy farms for the separated solids fraction remaining after the thin fraction is decanted and applied as the primary N source to grass.

With increasing demand for land and food, there is growing interest in sustainable intensification of agricultural production. Here we investigated sustainable intensification of grass and corn production for dairy farms using a system of semi-virtual farmlets that combine replicated field research plots with feed modelling. We improved manure N capture by spreading separated liquid fraction with a low emission sliding shoe applicator on grass, and manure P capture by precision injecting separated sludge into corn. Reducing the number of annual harvests (5 to 3) increased grass yield and inter-seeding Italian ryegrass in early maturing corn increased fall growth of the cover crop, thus helping to protect soil over winter and providing additional high quality herbage in spring. Irrigation improved yield and potentially yield stability of corn and grass, and adding a nitrification inhibitor to reduce N 2 O emission may help reduce pollution swapping especially from injected manure. Overall, allocating more land to corn than grass will increase farm productivity but effectiveness of measures to reduce pollution and pollution swapping need to be evaluated. Results show that good practices ensuring vigorous crops are challenging to implement but critical for achieving sustainable intensification. The semi-virtual farmlet system is very helpful for developing and evaluating sustainable production measures for corn and grass.

Ammonia (NH3) loss during field application of liquid manure (slurry) causes loss of nutrients for the crops and contributes to contamination of the environment. The emission can be mitigated by different low-emission application technologies and slurry treatment prior to application. It is assumed that a reduced area for air-slurry interaction will reduce the emission. The NH3 emission mitigation potential of technologies intended to reduce manure-air contact by reducing the exposed surface area (ESA) of the slurry or enhancing slurry infiltration was investigated for cattle slurry applied on grassland. Treatments tested were: 1) removing solids by solid-liquid separation of the slurry, 2) reduced ESA by narrow band application, and 3) application with a sub-surface-deposition (SSD) slurry application (creating aeration slots). For untreated cattle slurry NH3 emission was not reduced by reducing ESA, but application over aeration slots significantly decreased emission. However, reduced ESA by band application reduced emission from separated slurry compared to broadcast applied slurry, but no additional reduction was obtained by using the SSD technique. Lower emission was generally observed from separated slurry compared to untreated slurry for all application methods. This study shows that a reduction in NH3 emission is not necessarily obtained solely by reducing the ESA. It is hypothesized that rapid surface drying or crust formation of the untreated slurry in the relatively warm sunny conditions of these trials mitigated NH3 emission, thereby masking the effects of a reduced ESA. (C) 2021 The Author(s). Published by Elsevier Ltd on behalf of IAgrE.

Defining the long-term effects of liquid dairy manure (LDM) applied by a recommended low emission method is important to ensure sustainable grass production and dairy operations. We used natural abundance δ15N and conventional measurements in a long term field experiment to better understand the long-term fate of N applied as LDM, mineral fertilizer (MIN) and both (ALT). We investigated the effects of long-term applications of LDM (with low-emission trailing shoe), MIN, and alternating LDM and MIN (ALT) on grass N uptake, soil N stocks, N losses and δ15N natural abundance in grass, soil and fine heavy fraction (silt + clay size heavy soil). Nominal annual rates of total N were 200 and 400 kg ha−1 for MIN and 400 and 800 kg ha−1 for LDM. MIN and LDM (at 400 kg N ha−1) had similar NUE but LDM accumulated more total soil N (13% of applied) with less losses than MIN; ALT had high yields and losses. Herbage δ15N of MIN declined to near MIN levels after 10–15 years, indicating influence of pre trial management. Herbage δ15N of LDM was consistently lower than applied LDM, implying uptake of depleted urine N. High rates of enriched LDM had little effect on soil δ15N suggesting soil N was quite stable and enriched N was lost by non discriminating pathways like leaching. The physically protected fine heavy fraction contained most soil N. Clearer understanding of long-term N dynamics can improve sustainability of heavily fertilized perennial grasses on dairy farms.

Removing solids from dairy slurry improves grass N response and reduces soil loading of P and organic N which makes this practice useful for sustainable farming. Therefore, it is important to understand the effects of long-term applications on grass of separated dairy slurry on the growth and N response of a subsequent corn crop. This two-year field study investigated the residual effects after 11 years with applications on a perennial grass (Festuca arundinacea Schreb.) of whole (WS), separated dairy slurry (LF) obtained from the second stage of a two stage lagoon system, mineral fertilizer (Fert), WS plus Fert (WS/Fert), and Control (no fertilizer), on two subsequent crops of silage corn (Zea mays L.). In addition to the legacy nutrients, the corn received commercial fertilizer at rates 0, 100, 200 kg N ha(-1) or 200 kg N ha(-1) plus starter P (40 kg ha(-1)) at time of planting. Wholecrop yield and N uptake were determined at harvest stage. Over two years, corn yielded more with greater N and P uptake after long-term applications of WS than LF, Fert and WS/Fert, regardless of current fertilizer applications. Additional mineral fertilizer N and P did not substitute for the historical effects. There was a significant linear relationship of corn N uptake with historical applications of organic-N but not with mineral-N or total-N across current fertilizer treatments. These results support farmer practice of supplementing first-year corn, after long-term manure application on grassland, with modest N and P as starter application only and then increasing N rates thereafter.

Good soil quality implies the maintenance of properties at levels capable of ensuring an equilibrated and healthy ecosystem, with sustained agricultural production to supply the world population. Climate change, land-use change, and agriculture intensification are causing a decline in soil quality, which in most parts of the world is becoming severe (desertification). Land-use changes, the associated loss of soil organic matter (SOM), and beneficial microbial diversity are major reasons for deteriorating soil fertility and declining agricultural productivity, as well as affecting water, air, and biodiversity. Adaptation towards climate-resilient and climate-smart agriculture is necessary to cope with climate change and extreme events. This requires the following measures: (1) sustainable production (integrated livestock and cropping systems, including agroforestry); (2) increased soil organic matter (SOM) (bio-based and organic fertilizers, crop rotations, crop associations, no-till, conservation agriculture, C sequestration, and microbial processes); (3) reduced greenhouse gas emissions, less nutrient losses from agriculture, and increased nutrient use efficiency (NUE) (precision agriculture).

Subsurface tile drainage installation helps to maintain water table levels and to meet adequate crop moisture requirements. Artificial subsurface drainage continues to be a common practice in Newfoundland and Labrador (NL) and elsewhere around the world. The main objective of this study was to evaluate the performance of DRAINMOD in simulating water table depth (WTD) and water outflow from tile drained agricultural fields. This site on the Avalon Peninsula of Eastern Newfoundland has a rolling landscape with predominantly Podzolic soils. The tile drainage was installed at 1.0 m deep and spaced 12 m apart. Drainage outflows (two per plot) from twelve experimental plots (32 m x 60 m each) were monitored for two years. The simulated WTD ranged from 140 cm to 160 cm during rainfall season. The performance of the model was evaluated by the Index of agreement (IOA). It was 0.600 in 2017 and 0.559 in 2018. The result was considered to have acceptable accuracy, which can help to design or evaluate subsurface drainage systems in NL, Canada. However, further evaluation including additional sites are necessary to ensure optimum drainage design parameters for the major agricultural soils.

Cutting schedules affect forage yield, nutritive value, and persistence but few studies have recently assessed the effect of intensive cutting schedules on alfalfa (Medicago sativa L.)-based mixtures. We determined the effects of (a) cutting at early bud vs. early bloom of alfalfa, (b) a fall cut, (c) alfalfa-grass mixture vs. pure alfalfa, (d) one vs. two grasses, and (e) tall fescue (Schedonorus arundinacea [Schreb.] Dumort.) vs. timothy (Phleum pratense L.) in an experiment over four post-seeding years at four sites with four cutting schedules on four alfalfa-based mixtures. Cutting alfalfa at early bud rather than early bloom reduced annual forage dry matter (DM) yield by 2.03 Mg ha(-1) and alfalfa contribution to DM yield by 17 percentage units, increased forage total digestible nutrient (TDN) concentration by 44 g kg(-1) DM but did not increase estimated annual milk production per hectare. A fall cut did not improve annual forage DM yield and estimated annual milk production per hectare but reduced alfalfa contribution to DM yield. Pure alfalfa resulted in 1.09 Mg DM ha(-1) less annual forage DM yield than alfalfa grown with one or two grasses. Two forage grasses with alfalfa compared with just one grass had no effect on forage DM yield and estimated annual milk production per hectare. The response of forage DM yield and estimated annual milk production per hectare to timothy or tall fescue with alfalfa varied with site but forage TDN concentration and alfalfa contribution to DM yield were generally greater with timothy than tall fescue.