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Urban centres acquire and accumulate many materials from their hinterland, among these are nutrient elements such as nitrogen (N). The popular North American vision of a peri-urban setting is one where urban food production, composting and re-cycling are assumed to limit urban accumulation of nutrients. This study quantifies this assumption using the Lower Fraser Valley (LFV) of British Columbia as an example, ideal because it is surrounded by mountains, ocean and an international border which collectively delimit the peri-urban boundaries. Nitrogen influxes are dominated by livestock feed imports to support dairy and poultry production (18000 tonnes N), followed by human food imports (9210 tonnes N), as well as 5410 tonnes N as fertilizer and 4690 tonnes N in atmospheric deposition. There is a transfer of 6700 tonnes N from agricultural to urban ecosystems displacing food imports, but food production contributes to the N footprint of the LFV. Nitrogen effluxes are dominated by sewage disposal (10400 tonnes N), solid waste disposal (7020 tonnes N) and atmospheric emissions (9460 tonnes N). The total influx is 15 kg N per person, the net influx is 3.1 kg N per person. Per unit land area, these are a total influx of 24 kg N/ha and a net influx of 4.7 kg N/ha. The atmospheric emissions are 4.7 kg N per person and 7.2 kg/ha. The N in soil is mobile and it is assumed soil N is at a steady state concentration, thus the surplus N is lost from the soil, probably by leaching and runoff. The Fraser River is estimated to acquire and transport 5230 tonnes N from the region into the ocean each year, in addition to 10300 tonnes N from sewage outfall. This is coupled with effluxes of phosphorus (estimated previously), and the result probably has an impact on the coastal waters. There is little reuse of imported N and current waste management practices including composting and combustion do little to improve N efficiency. • The N budget is presented for a physically isolated peri-urban region. • N influxes were dominated by livestock feed to support local dairy and poultry. • N influxes for human food were the next most important. • N effluxes were dominated by sewage, atmospheric emissions and solid waste. • The total annual influx was 15 kg N per person, the net was 3.1 kg N per person. [ABSTRACT FROM AUTHOR]

Excess phosphorus (P) in peri-urban regions is an emerging issue, whereas there is global depletion of quality mined supplies of P. The flow of P across the landscape leading to regional surpluses and deficits is not well understood. We computed a regional P budget with internal P flows in a fairly discreet peri-urban region (Lower Fraser Valley, BC) with closely juxtaposed agricultural and non-agricultural urban ecosystems, in order to clarify the relationship between food production, food consumption and other activities involving use of P (e.g. keeping pets and horses and using soaps). We hypothesized changes that might notably improve P efficiency in peri-urban settings and wider regions. Livestock feed for the dairy and poultry sectors was the largest influx of P: the peri-urban land is too limited to grow feed grains and they are imported from outside the region. Fertilizer and import of food were the next largest influxes of P and a similar amount of P flows as food from the agricultural to urban ecosystems. Export of horticultural crops (berries and greenhouse crops) and poultry represented agricultural effluxes that partially offset the influxes. P efficiency was lower for horticultural production (21%) than animal production (32%), the latter benefited from importing feed crops, suggesting a regional advantage for animal products. There was 2.0, 3.8, 5.7 and 5.6 tonnes imported P per $ million farm cash receipts for horticulture, dairy, poultry meat and eggs. Eliminating fertilizer for corn and grass would reduce the ratio for the dairy industry. The net influx, dominated by fertilizer, animal feed and food was 8470 tonnes P per year or 3.2 kg P per person per year, and of this the addition to agricultural soils was 3650 tonnes P. The efflux in sewage effluent to the sea was 1150 tonnes P and exported sewage solids was 450 tonnes P. Municipal solid waste disposal was most difficult to quantify and was about 1800 tonnes P, 80% of which was partly reused in the urban regions and partly sequestered in landfill, which may be considered an efflux or a surplus. Reuse of rendering waste for feeding poultry significantly reduced P importation, but no rendering waste is used for cattle due to health concerns. Sensitivity analysis showed that variation in human population and the amount of P consumed per person in chicken and dairy products had the most influence on the total movement of P from agricultural to urban-ecosystems. There are current farm practices that mitigate P surpluses and new technologies are being developed to further reduce farm imbalances. However, current waste management policies that promote practices such composting of home wastes and exporting of poultry manure and biosolids to semiarid rangeland do little to enhance overall P cycling because the P is not returned to the farms producing feed and food for the peri-urban region. Sequestering in landfills may be a better solution until better ways are found to return surplus P. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3 ) emissions from agriculture to the atmosphere, along with emissions of other pollutants from a variety of sources, are of concern to agriculture worldwide. National emissions from agricultural sources in Canada are linked to domestic consumption and export demand for agricultural products. The onus to limit emissions is often directed to the producers, but the marketplace and consumer are also responsible for the environmental impact of their choices. This objective of this study was to quantitatively link agricultural NH 3 emissions to per person consumption of food and protein and to agricultural exports from Canada. There are substantial differences in the NH 3 emissions per unit consumed protein among the various food types. As a result, shifts in the Canadian diet have had a large impact on relative per person NH 3 emissions. From 1981 to 2006, the total per person protein intake in the Canadian diet increased about 5%, but NH 3 emission related to that diet decreased 20%. This is largely related to consumption of less beef, which has a high emission per unit of meat or protein, and more poultry and cereals which have much lower emissions. Although these changes in diet were not because of environmental concerns by the consumers, they had substantial effects on national-level emissions. These consumer driven effects may well exceed the possible effects of best management practices intended to address NH 3 emissions at the producer level. Note that the Canadian population has increased 50% from 1981 to 2006 and meat and egg exports increased 570%, so that total emissions from food production in Canada have increased. Our results imply there will be further effects on national NH 3 emissions because of dietary and export drivers that are generally outside the scope of agro-environmental policy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Estimates net organic and ammoniacal N content of manure in Canada. [•] Distinct differences among Ecoregions in the proportions of organic versus ammoniacal N. [•] Several best management practices (BMP) evaluated using recent costing information. [•] Relatively low-cost BMPs could save 1.6×107 kgNH3 for an estimated cost of $13M. [ABSTRACT FROM AUTHOR]

Abstract: National inventories of N emissions to the atmosphere from cattle depend on reliable information about husbandry practices, with appropriate spatial and temporal resolution. A survey of ∼1400 beef cattle farmers was used to quantify the prevalence of pasture and forage management practices that impact N intake and NH3 emissions, with implications for N2O emissions. These survey data were coupled to a mass balance model to inventory NH3 emissions by accounting for total ammoniacal (i.e., ammonia and ammonium) N (TAN) from excretion through to land spreading. As inputs, the model required excretion fractions, 2006 Canadian Census of Agriculture animal populations and detailed farm management practices from the survey. The N intake by grazing cattle was especially difficult to quantify. Early season grazing, when forages have elevated crude protein (>300gCP/kgdry matter), indicated potential for elevated emissions in May and June. Such exceptional CP concentrations during spring grazing may be important for N emissions, especially NH3. Additionally, beef cattle were reported by producers to spend 7–30%) of their time congregated, such as around water sources, feed or shade trees. This level of piosphere activity was attributed in the model to ∼20% increases in NH3 emissions relative to open pasture, and similar or higher effects would be expected for N2O emissions. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture–Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. [Copyright &y& Elsevier]

The objective of this study was to monitor ammonia emissions and develop updated ammonia emission factors for land application of poultry manure under British Columbia conditions. Field trials, which involved four types of poultry manure as the fertilizer materials, were performed at Agassiz Research Station in 2005 and 2006. After manure application, ammonia emission rates were determined using wind tunnels, capturing the emitted ammonia with acid traps and analyzing with a flow injection analyzer. For all trials, the highest emissions occurred within the first day, and gradually declined over the next 2-3 weeks. Cumulative ammonia emission in all treatments did not exceed the initial amount of ammonia- nitrogen present in manure. Ammonia emission rates were significantly different among the manure types (p<0.005). The percent total loss of ammonia with time was positively correlated with manure pH. Ammonia emission rates were generally higher in both of the spring trials than the fall trial. The proposed revised ammonia emission factors of 0.12 and 0.16 for the two major types of poultry - broiler and layer - are in line with current emission factors adopted by Environment Canada. However, current and revised emission factors (0.38 vs. 0.13) were substantially different for turkey manure. [ABSTRACT FROM AUTHOR]

The objective of this study was to monitor ammonia emissions and develop updated ammonia emission factors for land application of poultry manure under British Columbia conditions. Field trials, which involved four types of poultry manure as the fertilizer materials, were performed at Agassiz ResearchStation in 2005 and 2006. After manure application, ammonia emission rates were determined using wind tunnels, capturing the emitted ammonia with acid traps and analyzing witha flow injection analyzer. For all trials, the highest emissions occurred within the first day, and gradually declined over the next 2-3 weeks. Cumulative ammonia emission in all treatments did not exceed the initial amount of ammonianitrogen present in manure. Ammonia emission rates were significantly different among the manure types (p<0.005). The percent total loss of ammonia with time was positively correlated withmanure pH. Ammonia emission rates were generally higher in both of the spring trials than the fall trial. The proposed revised ammonia emission factors of 0.12 and 0.16 for the two major types of poultry - broiler and layer - are in line withcurrent emission factors adopted by Environment Canada. However, current and revised emission factors (0.38 vs. 0.13) were substantially different for turkey manure. [ABSTRACT FROM AUTHOR]

Abstract: Sleigh-foot application of slurry manure is the best method for applying slurry manure on many forage fields. This study was designed to assess agronomic effectiveness of multi-year surface banding of dairy slurry on a sward of tall fescue (Festuca arundinacea Schreb.). Our study showed that with this application technology, crop recovery of total-N from applied manure in the long-term is only about 77% that of mineral fertilizer. Despite relative inefficiency of N uptake from manure, yield response to manure equaled that to fertilizer at equivalent total-N rates although N-recovery was significantly lower. About 26–32% of applied manure-N was stored in soil organic matter and the buildup of soil-N was related to application rate of organic N. At moderate applications rates (approx. 400kgNha−1 a−1), soil N accumulated at about 120kgha−1 annually compared to 98kg ha−1 a−1 of unaccounted N, much of that probably volatilized and denitrified. Alternating between manure and fertilizer improved productivity per unit land area without increasing the rate of N non-recovery per unit of feed produced. [Copyright &y& Elsevier]

This study investigated the feasibility of altering the dietary cation-anion difference (DCAD) in grass by altering the grass variety and the amount and formulation of K fertilizer application. In experiment 1, treatments were combinations of 2 varieties (Barcel and HiMag) of tall fescue (Festuca arundinacea Schreb); 2 rates of K (0 and 250 kg/ha), supplied as KCl; and 2 rates of Mg (0 and 60 kg/ha), supplied as MgO. In experiment 2, K fertilizer was applied at 0 or 125 kg/ha as KCl or K2SO4. There was no difference between HiMag and Barcel tall fescue in the concentrations of Mg, S, and Cl. Application of K fertilizer decreased concentrations of Mg, but the magnitude of the decrease was not consistent across harvests. Conversely, application of Mg fertilizer increased Mg concentrations, but again, the magnitude of the increase was not consistent across harvests. The concentrations of Ca were higher in HiMag than in Barcel tall fescue, with the magnitude of the difference increasing from first to last harvest. Potassium fertilizer decreased Ca concentrations in the first, fourth, and fifth harvests only. Calcium concentration was decreased by a greater magnitude in HiMag tall fescue as a result of Mg fertilization. The HiMag tall fescue contained lower concentrations of K than did Barcel tall fescue in the first, second, and third harvests. Application of K fertilizer increased the K concentration in all 5 harvests but did not affect Na concentrations except in the last harvest. The HiMag tall fescue contained less Na than did Barcel, but the magnitude of the difference was affected by K and Mg fertilization. Application of K fertilizer decreased S concentrations in first-harvest grass, increased concentrations in second-and third-harvest grasses, and had no effect in fourth-or fifth-harvest grasses. Application of Mg fertilizer decreased S concentrations of tall fescue. Application of K fertilizer increased DCAD values for grass harvested from the second through fifth harvests. The increase in DCAD attributable to K fertilizer was less in HiMag than in Barcel tall fescue. Application of K fertilizer as K2SO4 increased dry matter yield and S concentrations of HiMag tall fescue, whereas K applied as KCl increased concentrations of K and Cl. There was no effect of fertilizer formulation on Na concentrations. The DCAD was lower in HiMag tall fescue fertilized with K2SO4 compared with that fertilized with KCl. This study showed that DCAD of grass can be manipulated by the choice of grass variety, fertilizer formulation, and fertilizer application rate. [ABSTRACT FROM AUTHOR]

Abstract: In order to improve understanding of how long-term use of manure affects nitrogen cycling processes, the effects of multiple years of manure applications on abundance of protozoa and nematode community structure were assessed. Plots of a grass sward in the Fraser Valley of British Columbia were either left untreated or were treated with dairy manure slurry or fertilizer, each at 50 or 100kg NH4–Nha−1, two to four times per year for six consecutive years. Nematode community structure and protozoan abundance were determined at 19 sample dates during the fourth (1997), fifth (1998) and sixth (1999) years of application. Protozoa, bacterivorous nematodes and fungivorous nematodes were consistently more abundant in soil treated with manure at both rates than in fertilized and untreated soil, indicating that microbial turnover and flux of nutrients through the soil food web was enhanced in manured soil relative to fertilized or untreated soil. The Maturity Index (MI) and the MI2-5 were both reduced by fertilization and manure, relative to the control. The MI for the manure treatment was lower than for the fertilizer treatment as a result of greater relative abundance of enrichment opportunist nematodes in manure-treated soil. Accordingly, the MI2-5 did not differ between the manure and fertilizer treatments, suggesting that with the exception of enrichment opportunists fertilizer and manure have similar effects on structural complexity of the soil food web. Populations of micro-fauna were also assessed through 1998 and 1999 in subplots that had been treated with manure or fertilizer for four years and stopped receiving manure or fertilizer in 1998, and in subplots given manure in 1998 that had previously either been fertilized or left untreated. Protozoa and bacterivorous and fungivorous nematodes remained more abundant through 1998 and 1999 in previously manure-treated plots than in previously fertilized plots, indicating that the cumulative effects of manure application on enhancement of microbial production can be detected through at least two growing seasons after applications cease. Application of manure for one year to previously non-treated or fertilized soil raised the abundance of protozoa and bacterivorous and fungivorous nematodes to levels comparable to continuously manured soil. [Copyright &y& Elsevier]

Abstract: Plots of a tall fescue (Festuca arundinacea) sward in the south coastal region of BC, Canada, were treated with dairy manure slurry or fertilizer at 50 or 100kgNH4-Nha−1 up to four times per year for six consecutive years; control plots received no manure or fertilizer. The length of fungal hyphae and abundance of bacterial cells were determined by direct counting at 19 sample dates during the fourth (1997), fifth (1998) and sixth (1999) application years. Bacterial abundance was significantly greater in manured soil than in fertilized and untreated soils. In contrast, hyphal length was significantly greater in untreated soil than in manured and fertilized soils. In subplots that ceased to receive manure in 1998, bacterial abundance remained greater through 1998 and 1999 than in previously fertilized plots, indicating that the 4 year cumulative effect of manure was detectable for at least two growing seasons after applications cease. The apparently negative effect of manure and fertilizer on fungal hyphae also appeared to persist through 2 years after applications ceased. Bacterial abundance increased after an initial application of manure for 1 year to previously untreated plots, but not to levels comparable to plots treated with manure continuously from 1994 to 1998. Increases in bacterial abundance, during the one to three week intervals immediately following individual applications of manure, were inconsistent and other factors, such as soil moisture, temperature and perhaps crop phenology appear to have had strong effects on the timing of these microbial responses. Annual means for bacterial abundance and total microbial biomass in the continuous manure treatment were similar for all 3 years. This suggested that the manure-induced increase in microbial biomass probably reached a plateau between one and 3 years after applications commenced. The large bacterial populations along with abundant carbon substrates in manured soil, relative to fertilized soil, were probably capable of immobilizing influxes of mineral N, explaining the observations that less leaching occured from manured than from fertilized soils. [Copyright &y& Elsevier]

• Historical slurry applications to grassland improve corn response to applied N and P. • Historical applications of separated slurry had less corn response than whole slurry. • Historical treatments have impact on corn even with current fertilizer application. • Corn performance responded linearly to historical application rates of organic-N. 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. Whole-crop 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. [ABSTRACT FROM AUTHOR]

Orchardgrass (Dactylis glomerata L.) is a major component of many pastures in temperate North America. Early and profuse flowering in pastures is problematic due to livestock refusal to consume flowering stems. The objective of this research was to determine the stability and agronomic impact of recently developed sparse-flowering orchardgrass populations across temperate North America. Six cultivars, three sparse flowering and three normal flowering, were grown at 21 locations in temperate North America and evaluated for panicle density, heading date, and forage yield. Sparse-flowering cultivars had 57% fewer panicles than normal-flowering cultivars, but this effect was highly dependent on mean winter temperature, with normal-flowering cultivars showing twice as much temperature sensitivity compared to sparse-flowering cultivars. Forage yield of sparse-flowering cultivars was reduced by approximately 24 to 32% for first harvest and 2 to 9% for regrowth harvests compared to normal-flowering cultivars and this reduction in forage yield was independent of mean winter temperature. The forage yield reduction associated with sparse flowering is most likely due to a combination of physiological load (loss of stems) and opportunity cost (lack of selection pressure for yield), suggesting an opportunity to improve forage yield potential of this sparseflowering germplasm pool. [ABSTRACT FROM AUTHOR]

Carabid populations were assessed in relation to type and level of nutrient input in a multi-year trial on tall fescue, Festuca arundinacea. Thirteen species of carabids were recovered, Pterostichus melanarius representing 81% of all catches. In 3 m wide strip plots populations of P. melanarius increased with the rate of dairy slurry application, and the effect persisted for 2 years after applications ceased. The numerical response of P. melanarius to dairy slurry required several months, with other carabid species being largely unaffected by the treatments. Species diversity decreased with the number of years of dairy slurry application and with increasing application rates, and the effect persisted for 2 years. The decline in diversity was usually caused by changes in numbers of P. melanarius. Chemical fertilizer had no effect on carabid populations compared to controls. Earthworm biomass increased with increasing dairy slurry rate. The predatory capacity of the carabids increased with increasing dairy slurry rate, and the proportion of onion maggot pupae, Delia antiqua, consumed increased with P. melanarius numbers. The application of dairy slurry may therefore be used to improve pest control in forage grass. [Copyright &y& Elsevier]

Background: 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). Methods: 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. Results: 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. Conclusion: Clearer understanding of long-term N dynamics can improve sustainability of heavily fertilized perennial grasses on dairy farms. [ABSTRACT FROM AUTHOR]

Agriculture produces food, fiber and biofuels for the world's growing population, however, agriculture can be a major contributor of nitrogen (N) losses including emissions of ammonia (NH 3), nitrous oxide (N 2 O) and nitrate (NO 3 −) leaching and runoff. A Canadian Agricultural Nitrogen Budget for Reactive N (CANBNr) model was developed to estimate the soil N balance in 3487 soil landscape of Canada polygons from 1981 to 2016. The CANBNr model integrates NH 3 emission from fertilizers, manure from housing, storage and field, as well as direct/indirect N 2 O emissions from fertilizers, manures, crop residues and soil organic matter. The NO 3 − leaching is estimated based on the residual soil N (RSN) at harvest and drainage derived with the DeNitrification-DeComposition (DNDC) model. From 1981 to 2016, the N input from fertilizer and N fixation increased at a greater rate than N removal in harvested crops in all provinces of Canada, resulting in an increase in the RSN and N losses. In 2016, the Prairie provinces had lower N losses (11.7 kg N ha−1) from N 2 O, NH 3 and NO 3 − compared with 43.2 kg N ha−1 in central Canada, and 76.5 kg N ha−1 in Atlantic Canada. However, the Prairie provinces had 84.3% of the total Canadian farmland (74.3% of the total Canadian N input), while central Canada had 12.9% of Canadian farmland (21.7% of the total Canadian N input). In the Prairie provinces, the total N 2 O loss from fertilizer N ranged 4.4–8.6 Gg N whereas NH 3 loss ranged from 17.1 to 44.6 Gg N and these values were influenced by both emission intensity and total land area. Total N 2 O losses from manure were highest in Alberta, Ontario and Quebec resulting in 4.8, 4.4, and 3.4 Gg N and NH 3 losses from manure were also highest in these 3 provinces at 61.1, 45.2 and 40.4 Gg N, respectively. Nitrate leaching was impacted by drainage volumes, soil type and N inputs. In the non-growing season, NO 3 − leaching losses (36-yr average) were 63.3 Gg in Ontario and 57.5 Gg N in Quebec compared with 20.8 Gg N for Ontario and 35.5 Gg N for Quebec in the growing season. In contrast, the Prairie provinces showed higher NO 3 − leaching in the growing season (23.1–37.4 Gg N) than in the non-growing season (10.4–13.7 Gg N). In summary, total fertilizer N increased the most over the 36 years in the Prairies which resulted in increased RSN and N leaching losses that will require further intervention. [Display omitted] • Canadian Agricultural Nitrogen Budget for Reactive N (CANBNr) model was developed. • The N budget were simulated at 3487 soil landscape of Canada polygons from 1981 to 2016. • RSN and N losses increased due to the greater increase in N input from fertilizer and N fixation than N removal by crop. • The Prairie provinces had lower N 2 O, NH 3 and NO 3 − leaching losses per hectare farmland than other provinces. [ABSTRACT FROM AUTHOR]

Recent developments in composting technology enable dairy farms to produce their own bedding from composted manure. This management practice alters the fate of carbon and nitrogen; however, there is little data available documenting how gaseous emissions are impacted. This study measured in-situ emissions of methane (CH 4 ), carbon dioxide (CO 2 ), nitrous oxide (N 2 O), and ammonia (NH 3 ) from an on-farm solid-liquid separation system followed by continuously-turned plug-flow composting over three seasons. Emissions were measured separately from the continuously-turned compost phase, and the compost-storage phase prior to the compost being used for cattle bedding. Active composting had low emissions of N 2 O and CH 4 with most carbon being emitted as CO 2 -C and most N emitted as NH 3 -N. Compost storage had higher CH 4 and N 2 O emissions than the active phase, while NH 3 was emitted at a lower rate, and CO 2 was similar. Overall, combining both the active composting and storage phases, the mean total emissions were 3.9 × 10 −2 g CH 4 kg −1 raw manure (RM), 11.3 g CO 2 kg −1 RM, 2.5 × 10 −4 g N 2 O kg −1 RM, and 0.13 g NH 3 kg −1 RM. Emissions with solid-separation and composting were compared to calculated emissions for a traditional (unseparated) liquid manure storage tank. The total greenhouse gas emissions (CH 4 + N 2 O) from solid separation, composting, compost storage, and separated liquid storage were reduced substantially on a CO 2 -equivalent basis compared to traditional liquid storage. Solid-liquid separation and well-managed composting could mitigate overall greenhouse gas emissions; however, an environmental trade off was that NH 3 was emitted at higher rates from the continuously turned composter than reported values for traditional storage. [ABSTRACT FROM AUTHOR]

Orchardgrass (Dactylis glomerata L.) is a major component of many pastures in temperate North America. Early and profuse flowering in pastures is problematic, because livestock refuse to consume flowering stems, prompting many graziers to simply avoid using this species. The objective of this research was to determine the impact of reduced flowering on the quality of harvested forage under two harvest managements of orchardgrass. Six cultivars, three normal cultivars and three sparse-flowering cultivars (mean panicle density of 141 vs. 61 panicles m-2, respectively), were evaluated in field experiments at 21 locations in North America under a 3-cut harvest management. These cultivars were also evaluated at seven locations under a 5-cut harvest management. Sparseflowering cultivars averaged 9% greater crude protein (CP), 3% lower neutral detergent fiber (NDF), 2% greater NDF digestibility, and 2% greater in vitro dry matter digestibility (IVDMD) than normal cultivars. For the two digestibility measures, differential panicle density between the cultivar groups explained a significant portion of variability, indicating that the increase in forage quality was proportional to the decrease in panicle density below a threshold of about 50 panicles m-2. Lastly, differences in regrowth forage quality between cultivar groups were smaller, less consistent, and of lesser statistical significance than for first harvest. While selection for sparse flowering in orchardgrass resulted in significant cause-and-effect increases in firstharvest forage quality, these effects were too small to offset the reduced forage yield associated with the sparse-flowering trait. [ABSTRACT FROM AUTHOR]

Abstract: Controlled release urea (CRU) has been shown to improve nitrogen fertilizer use efficiency in a number of production systems. However, the effectiveness of CRU will be strongly affected by the environmental conditions of the region. Research trials were conducted at five locations across four major ecoregions spanning 1600km across the Northern Great Plains and Pacific Maritimes of North America from 2004 to 2006 to evaluate the effects of a single application of polymer-coated urea (CRU) or split applications of urea fertilizer as compared with non-coated urea for their effects on crop growth, crop N concentration, and crop N accumulation of wheat (Triticum aestivum L.), barley (Hordeum vulagre L.) canola (Brassica napus L.) and corn (Zea mays L.) across a wide range of environmental conditions. Urea applied as an in-soil band at the time of seeding was generally as or more effective than similarly placed CRU, split application of urea or blended urea and CRU in the semi-arid Mixed Grassland, moist Aspen Parkland or wet Boreal Transition ecoregions in increasing early season dry matter yield and seed or grain yield of canola, wheat or barley. Similarly, broadcast urea was as or more effective than broadcast CRU, split applications or blended applications in increasing corn dry matter yield under the wet conditions in the Lower Mainland ecoregion. There were some situations where use of split applications or use of the CRU in a blend with the non-coated urea resulted in increases in grain yield as compared to the non-coated urea, primarily under moist conditions in the Boreal Transition or Aspen Parkland ecoregions. Some yield losses occurred from use of the CRU as compared with the non-coated urea and were attributed to delays in release of N from the granule that limited early season N availability and crop growth, especially in corn with a high N demand. Effects on grain N concentration and accumulation of N in the crop at harvest were mixed, with the CRU, blended applications of CRU and urea or split applications occasionally producing higher grain N concentration and N accumulation in the crop than the non-coated urea. Benefits of CRU on grain N concentration were more frequent than benefits on grain yield, but were not large or consistent. Response of crop growth and N uptake to N management was generally similar under CT and RT, with occasional differences occurring due to changes in yield potential or N deficit associated with the differences in tillage management. Therefore, under growing conditions across a wide range of ecoregions in the Northern Great Plains and the Pacific Maritimes, the use of CRU or split applications do not appear to provide a consistent improvement in crop yield, N concentration in the grain, total N accumulation at harvest, or nitrogen use efficiency as compared to standard regional timing and placement of non-coated urea. [Copyright &y& Elsevier]

Two experiments were conducted to evaluate the potential to use leaf chlorophyll index (LCI), measured using a Minolta SPAD-502 meter, for making fertilizer nitrogen (N) recommendations for silage corn in a high N fertility environment. In Experiment 1, treatments were 0, 40, 80, 120, 160, and 200 kg N ha[sup -1] as NH[sub 4]NO[sub 3] broadcast at corn emergence. At the six-leaf stage, soil inorganic N to 90cm depth, total Kjeldahl N concentration of the fifth leaf, sixth leaf, and the above-ground portion of the plant, and LCI of the fifth and sixth leaves, were determined. In Experiment 2, LCI and LCIR (ratio of LCI to LCI from a reference plot receiving 200 kg N ha[sup -1] at corn emergence) were measured at approximately the six-leaf stage in 87 trials 1994-1996. Treatments consisted of different fertilizer N rates applied at sidedress, and corn yield and pre-sidedress soil nitrate test (PSNT) values were determined. In Experiment 1, nitrogen concentration of the above-ground plant increased with increasing soil inorganic N content up to about 350kg Nha[sup -1], and LCI generally increased linearly with leaf total N concentration. However, the relationship between LCI and leaf N concentration varied among years, and the relationship between leaf total N concentration and above-ground plant total N concentration was inconsistent. In Experiment 2, above-ground plant total N concentration was a poor predictor of soil inorganic N supply and corn relative yield when measured over a number of trials. Leaf chlorophyll index at the six-leaf stage therefore has significant limitations as an indicator of corn N status or soil inorganic N supply. Despite these limitations, LCI had a 68% success rate in identifying fields which were responsive and unresponsive to sidedress N using a critical LCI value of 43.7 SPAD units. This success rate is similar to that obtained with the PSNT. However, LCI cannot be used to recommend rates of fertilizer N for LCI values below the... [ABSTRACT FROM AUTHOR]

The purpose of this study was to measure corn response to nitrogen (N), to evaluate the feasibility of using the pre-sidedress soil nitrate test (PSNT) for making fertilizer N recommendations for silage corn, and to evaluate the environmental and economic implications of adopting fertilizer N recommendations based on the PSNT in south coastal British Columbia, Canada, a region of high soil N fertility. Eighty-seven trials were conducted from 1994-1996 with corn or forage grass as a preceding crop on fields having a history of manure application. Non-manured trials received no spring manure application whereas manured trials received a spring application typical of that farm field. In 1994, treatments included sidedress N rates of 0, 30, 60, 90, 120, and 150kg N ha-[SUP1] replicated twice. In 1995 and 1996, trials with less than 30mg NO[SUB3]-N kg[SUB-1] soil to 30cm depth prior to sidedress received the same treatments as in 1994, whereas trials with concentrations above this value received two treatments, 0 and 150kgNha[SUP-1] replicated four times. Trials received less than 50kgN ha[SUP-1] at planting. Yield response to sidedress N was limited, with 71, 87, and 55% of trials with 90% or higher relative yield (yield at 0kgNha[SUP-1] divided by yield at 150kgNha[SUP-1]) in 1994, 1995 and 1996, respectively. The limited yield response was attributed to high soil N mineralization, which averaged 166 and 146kgNha[SUP-1] for non-manured trials in 1995 and 1996, respectively. The critical PSNT value (above which no yield response to sidedress N is expected) was predicted to be 19 and 23 mg NO[SUB3]-Nkg[SUP-1] soil using the Cate-Nelson procedure and a linear-plateau regression procedure, respectively. A critical PSNT test value of 32 mg NO[SUB3]-N kg[SUP-1] soil was predicted using a linear-plateau regression of the estimated N rate which would maximize economic return (N[SUBMER]) against PSNT test value. In addition, a model designed to minimize the risk of yield... [ABSTRACT FROM AUTHOR]

• Above-ground biomass and soil temperature were well simulated using DNDC across sites. • DNDC showed reasonable performances in estimating soil water and inorganic N contents. • DNDC captured the manure application timing and rate impacts on total N 2 O emissions. • Daily N 2 O simulations may be improved by integrating N 2 O diffusivity and consumption. It is uncertain whether process-based models are currently capable of simulating the complex soil, plant, climate, manure management interactions that influence soil nitrous oxide (N 2 O) emissions from perennial cropping systems. The objectives of this study were (1) to calibrate and evaluate the DeNitrification DeComposition (DNDC) model using multi-year datasets of measured nitrous oxide (N 2 O) fluxes, soil moisture, soil inorganic nitrogen, biomass and soil temperature from managed grasslands applied with manure slurry in contrasting climates of Canada, and (2) to simulate the impact of different manure management practices on N 2 O emissions including slurry application i) rates (for both single vs. split); and ii) timing (e.g., early vs. late spring). DNDC showed "fair" to "excellent" performance in simulating biomass (4.7% ≤ normalized root mean square error (NRMSE) ≤ 29.8%; −9.5% ≤ normalized average relative error (NARE) ≤ 16.1%) and "good" performance in simulating soil temperature (13.2% ≤ NRMSE ≤ 18.1%; −0.7% ≤ NARE ≤ 10.8%) across all treatments and sites. However, the model only showed "acceptable" performances in estimating soil water and inorganic N contents which was partially attributed to the limitation of a cascade water sub-model and inaccuracies in simulating root development/uptake. Although, the DNDC model only demonstrated "fair" performance in simulating daily N 2 O fluxes, it generally captured the impact of the timing and rate of slurry application and soil texture (loam vs. sandy loam) on total N 2 O emissions. The DNDC model simulated N 2 O emissions from spring better than split manure application (fall and spring) at the Manitoba site partially due to the overestimation of available substrates for microbial denitrification from fall application during the wet spring periods. Although DNDC performed adequately for simulating most of the manure management impacts considered in this study we recommend improvements in the simulation of soil freeze-thaw cycles, manure decomposition dynamics, soil water storage, rainfall canopy interception, and microbial denitrification and nitrification activities in grasslands. [ABSTRACT FROM AUTHOR]