ALBERT

Description: Efficient liquid manure application systems that minimize ammonia volatilization are required for use on perennial forage grasses. Ammonia volatilization was monitored using wind tunnels for 10 d after three pig slurry applications using four boom-mounted applicators: a broadcast splash-plate system, a trailing-shoe system and a drag-hose system with and without previous soil aeration. Average losses of 32, 20 and 15% of the total ammonia-N (TAN) applied to plots were observed for the splash-plate, the trailing-shoe and the drag-hose systems, respectively. The grass canopy intercepted, on average, 14% of pig slurry TAN using the splash-plate system compared with 4% for the trailing-shoe and 5% for the drag-hose systems. Reductions in canopy interception explained 58% of differences in volatilization rates among the application systems. On two of three application dates, NH3 volatilization was lower using the drag-hose than the trailing-shoe system. This was attributed to the sealing of the soil surface by the passage of the trailing-shoe, which decreased slurry infiltration rate. Ammonia volatilization was not reduced by soil aeration prior to slurry application using a drag-hose system likely because aeration did not increase slurry infiltration into the soil. Producers could be advised to reduce volatilization losses by using a simple drag-hose system to avoid application of slurry to leaf canopies. Key words: Ammonia volatilization, liquid hog manure, pig slurry, application method, ammonium

Description: Greenhouse gas emissions from farms can be suppressed in two ways: by curtailing the release of these gases (especially N2O and CH4), and by storing more carbon in soils, thereby removing atmospheric CO2. But most practices have multiple interactive effects on emissions throughout a farm. We describe an approach for identifying practices that best reduce net, whole-farm emissions. We propose to develop a “Virtual Farm”, a series of interconnected algorithms that predict net emissions from flows of carbon, nitrogen, and energy. The Virtual Farm would consist of three elements: descriptors, which characterize the farm; algorithms, which calculate emissions from components of the farm; and an integrator, which links the algorithms to each other and the descriptors, generating whole-farm estimates. Ideally, the Virtual Farm will be: boundary-explicit, with single farms as the fundamental unit; adaptable to diverse farm types; modular in design; simple and transparent; dependent on minimal, attainable inputs; internally consistent; compatible with models developed elsewhere; and dynamic (“seeing”into the past and the future). The Virtual Farm would be constructed via two parallel streams - measurement and modeling - conducted iteratively. The understanding built into the Virtual Farm may eventually be applied to issues beyond greenhouse gas mitigation. Key words: CO2, N2O, CH4, agroecosystems, models, climate change

Description: Forest managers are faced with complicated road construction and deactivation decisions. When construction, upgrading, and deactivation strategies must be determined simultaneously over broad spatial and temporal scales, the problem becomes very complex and decision support systems are needed. In this paper, we report the development and application of an optimal road class and deactivation model using dynamic programming. We tested our model on projected road networks on Hardwicke Island, British Columbia. Sensitivity of inputs such as construction costs, upgrade costs, hauling and maintenance costs, deactivation costs, length of time horizon, discount rate, and haul volume were tested within and between two road networks. Comparison of road networks revealed that haul volume concentration, average haul distance, and total road length are the most important variables that affect road class decisions and total network costs. Within our case study, the road network with the lowest average hauling distance resulted in the lowest total cost (CAN$0.24/m3 less), because hauling costs are the largest component (46%) of total transportation costs. The dynamic programming model can be used to assess numerous road construction and maintenance assumptions under various silviculture and harvest systems.

Description: We examined fifth-year seedling response to soil disturbance and vegetation control at 42 experimental locations representing 25 replicated studies within the North American Long-Term Soil Productivity (LTSP) program. These studies share a common experimental design while encompassing a wide range of climate, site conditions, and forest types. Whole-tree harvest had limited effects on planted seedling performance compared with the effects of stem-only harvest (the control); slight increases in survival were usually offset by decreases in growth. Forest-floor removal improved seedling survival and increased growth in Mediterranean climates, but reduced growth on productive, nutrient-limited, warmhumid sites. Soil compaction with intact forest floors usually benefited conifer survival and growth, regardless of climate or species. Compaction combined with forest-floor removal generally increased survival, had limited effects on individual tree growth, and increased stand growth in Mediterranean climates. Vegetation control benefited seedling growth in all treatments, particularly on more productive sites, but did not affect survival or alter the relative impact of organic matter removal and compaction on growth. Organic matter removal increased aspen coppice densities and, as with compaction, reduced aspen growth.

Description: The impact of forest management operations on soil physical properties is important to understand, since management can significantly change site productivity by altering root growth potential, water infiltration and soil erosion, and water and nutrient availability. We studied soil bulk density and strength changes as indicators of soil compaction before harvesting and 1 and 5 years after harvest and site treatment on 12 of the North American Long-Term Soil Productivity sites. Severe soil compaction treatments approached root-limiting bulk densities for each soil texture, while moderate compaction levels were between severe and preharvest values. Immediately after harvesting, soil bulk density on the severely compacted plots ranged from 1% less than to 58% higher than preharvest levels across all sites. Soil compaction increases were noticeable to a depth of 30 cm. After 5 years, bulk density recovery on coarse-textured soils was evident in the surface (010 cm) soil, but recovery was less in the subsoil (1030 cm depth); fine-textured soils exhibited little recovery. When measured as a percentage, initial bulk density increases were greater on fine-textured soils than on coarser-textured soils and were mainly due to higher initial bulk density values in coarse-textured soils. Development of soil monitoring methods applicable to all soil types may not be appropriate, and more site-specific techniques may be needed for soil monitoring after disturbance.

Description: The sustainability of organic dairying in Canada, with respect to nutrients, remains unexamined. To assess how management affects nutrient status, we documented whole farm nutrient (NPK) budgets over 2 yr (2003 to 2005) and soil (0 to 15 cm) P and K status on 15 long-term Ontario organic dairy farms. Farm size, livestock density and herd productivity averaged 110 ha, 1.00 livestock units ha-1 and 5656 kg milk cow-1 yr-1, respectively. Annual farm nutrient surpluses of 75 (N), 1 (P) and 11 (K) kg ha-1 yr-1 were lower than those reported for confinement-based dairy farms in the United States, pointing to possible environmental benefits from reduced off farm impacts on air and water quality. Weighted average soil test P levels were low (〈 10 mg kg-1) on approximately 50% of farms, while exchangeable K levels were moderate to high (76 to 160 mg kg-1) on all farms. Four farms adopting a "self-sufficient" approach, producing most feed on-farm, imported little P as feed (1.37 to 1.90 kg P ha-1 yr-1) and had negative average farm P balances (avg. -1.54 kg P ha-1 yr-1). An integrated nutrient management approach, along with a flexible feed import strategy, fosters the sustainability of organic dairying systems. Key words: Organic dairying, nutrient budget, nitrogen, potassium, phosphorus, soil fertility

Description: International initiatives such as the United Nations Framework Convention on Climate Change and the Kyoto Protocol require that countries calculate national inventories of their greenhouse gas emissions. The objective of the present study was to develop a country-specific (Tier II) methodology to calculate the inventory of N2O emissions from agricultural soils in Canada. Regional fertilizer-induced emission factors (EFreg) were first determined using available field experimental data. Values for EFreg were 0.0016 kg N2O-N kg-1 N in the semi-arid Brown and 0.008 kg N2O-N kg N-1 in the sub-humid Black soil zones of the Prairie region, and 0.017 kg N2O-N kg-1 N in the humid provinces of Quebec and Ontario. A function relating EFreg to the "precipitation to potential evapotranspiration" ratio was determined to estimate annual emission factors (EFeco) at the ecodistrict scale (≈ 150 000 ha) in all agricultural regions of Canada. Country-specific coefficients were also developed to account for the effect of several additional factors on soil N2O emissions. Emissions from fine-textured soils were estimated as being 50% greater than from coarse- and medium-textured soils in eastern Canada; emissions during winter and spring thaw corresponded to 40% of emissions during the snow-free season in eastern Canada; increased emissions from lower (wetter) sections of the landscape and irrigated areas were accounted for; emissions from no-till soils were 10% greater in eastern, but 20% lower in western Canada than from those under conventional tillage practices; emissions under summerfallow were estimated as being equal to those from soils under annual cropping. This country-specific methodology therefore accounts for regional climatic and land use impacts on N2O emission factors, and includes several sources/offsets that are not included in the Intergovernmental Panel on Climate Change (IPCC) default approach. Key words: Nitrous oxide, soils, greenhouse gases, inventory

Description: Fast-growing hybrid poplars are being planted in the Canadian prairies to meet the increasing demand for fibre and environmental services of trees and forests; however, the impact of hybrid poplars on C dynamics and storage on previously farmed land is largely unknown for the boreal region. We measured soil CO2 efflux along a chronosequence (3-, 9-, and 11-yr-old stands) of hybrid poplar (Populus deltoides × Populus × petrowskyana var. Walker) plantations and a control agricultural field from June to August 2004. Measurements were made between 0800 and 1800 with a portable Li-Cor 6400-09 system and were based on 4–5 min averaging. We also measured the response to simulated rainfall and the diurnal fluctuation of soil CO2 efflux. Soil CO2 efflux ranged from 1.30 µmol CO2 m-2 s-1 in the 3-yr old plantation to 5.41 µmol CO2 m-2 s-1 in the agricultural control field, or from 0.17 ìmol CO2 m-2 s-1 kg-1 C (based on soil organic C content to a 0.4 m depth) in the 3-yr-old plantation to 1.09 µmol CO2 m-2 s-1 kg-1 C in the 11-yr-old plantation. Simulated rainfall applied in the 3-yr-old plantation and a newly planted site resulted in an immediate pulse of CO2 efflux, 2.90 and 2.54 µmol CO2 m-2 s-1, respectively, followed by an efflux rate sustained slightly above pre-irrigation levels. No secondary pulse of soil respiration was observed in the 2-h period following water application. Diurnal variation of soil respiration was found to be small between 0600 and 1900 in the agricultural control field, with values that varied from 2.66 to 3.17 µmol CO2 m-2 s-1. Continued monitoring of soil respiration and other C cycling processes in the chronosequence will improve our understanding of the potential for C sequestration in hybrid poplar plantations in northern Alberta. Key words: Carbon sequestration, greenhouse gas emissions, biomass, boreal forest, land-use change, hybrid poplar

Description: One of the key factors in phosphorus management is the P retention capacity (PRC) of the soil. In our previous study, we formulated several equations for estimating the phosphorus retention capacity of Manitoba soils. The objectives of the current study were to evaluate these equations using independent soil samples and to evaluate the influence of manure application on the predictive ability of these equations. Forty representative surface soil samples (20 soils with history of manure application and 20 without manure application history) were collected from across Manitoba. The P retention index (P150) and Langmuir adsorption maximum (Smax) were determined in the laboratory. The measured P retention capacities were then compared with those estimated using the formulated equations. Surprisingly, P150, which was obtained from a single measurement, was more robust than Smax that was obtained from at least 17 measurements as the equations provided a better estimate of P150 than Smax. Equations that were based on soil particle sizes (either percent clay or percent sand) provided poor estimates of soil PRC for the whole soil collection. However, when the soils were grouped on a pH basis, soil particle size worked better for soils with pH

Description: Rehabilitation of skid trails, temporary roads, and log landings is required for many harvested sites in British Columbia; however, more information is needed regarding practical methods to return these access areas to productive forest. Lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seedlings (1 + 0) were planted into (i) fully rehabilitated landings (burn-pile debris and topsoil incorporated), (ii) tilled landings, and (iii) unprepared portions of the adjacent cutblock. After two seasons of growth in the field, seedlings planted on fully rehabilitated landings were 38% larger, more robust, and exhibited 44% greater absolute growth and 22% greater relative growth rates, than seedlings planted in the adjacent cutblock. Seedlings planted on tilled landings were 33% smaller, and exhibited absolute growth rates 38% less, and relative growth rates 18% less, than seedlings planted in the adjacent cutblock. Seedlings planted in the cutblock exhibited higher ectomycorrhizal colonization rates. Our results indicate that tillage alone was not sufficient to fully rehabilitate these landings, but that incorporation of recovered topsoil and burn-pile debris produced an excellent growth substrate. This method, using materials found on site, can prevent a significant loss of land regenerating to productive second-growth forest.