• Authors:
    • Young, M. A.
    • Roy, J. L.
    • Bekele, A.
  • Source: Soil Science
  • Volume: 178
  • Issue: 7
  • Year: 2013
  • Summary: Topsoil (TS) shortage often limits the successful reclamation of older mined sites. We evaluated the effectiveness of one-time application of biochar or oxidized lignite (humalite) alone or in combination with a mix of conventional organic materials to reconstruct functioning TS using subsoil (SS) as a substrate. Biochar or humalite carbon (C) represented a stable form of C, whereas C from a mix of sawdust, wheat straw, and alfalfa (labile organic mix (LOM)) represented the labile C fraction. The amount and composition of organic amendment mix were determined so that organic C levels of reconstructed TS would be equivalent to that of the native TS in the long-term. Three SS substrates differing in texture (clay, loam, and sand) and organic C levels were used in the study. We used field pea (Pisum sativum L.) and barley (Hordeum vulgare L.) as test crops in rotation in four sequential greenhouse studies. All treatments except the control SS and TS received supplemental fertilizer nutrients. Plant biomass yield and tissue concentrations were evaluated at the end of each study, whereas soil nutrient levels were assessed at the end of Study II and Study IV. Labile organic mix amendment alone was superior in biomass production relative to any of the other treatments at the early stages of the study. Cumulative biomass yield of SS amended with either biochar or humalite in the presence of LOM was statistically identical for clay and sand soils. These values were also statistically indistinguishable from the fertilized native TS control treatment for the clay soil but not for the sand soil. Humalite application at a high rate (76 g/kg soil) increased soil CEC, decreased soil pH and P concentration, and increased both soil and plant tissue B concentrations. Our data show that a functioning TS can be reconstructed using either biochar or humalite in the presence of LOM and adequate supplemental fertilizers particularly N and P. Detailed characterization of organic amendments is recommended to avoid undesirable effects emanating from their use. Field-based long-term studies are needed to confirm the longevity of benefits of using these amendments.
  • Authors:
    • Amiro, B. D.
    • Fraser, T. J.
  • Source: Canadian Journal of Soil Science
  • Volume: 93
  • Issue: 3
  • Year: 2013
  • Summary: Sequestering atmospheric carbon in agricultural soil is an attractive option for mitigation of rising atmospheric carbon dioxide concentrations. Perennial crops are more likely to gain carbon whereas annual crops are more likely to lose carbon. A pair of eddy covariance towers were set up near Winnipeg Manitoba, Canada, to measure the carbon dioxide flux over adjacent paired perennial grass hay fields with high soil organic carbon. A Treatment field was converted to annual cropping by spraying with herbicide, cutting and tilling. A Control field was cut, but allowed to re-grow. Differences in net ecosystem productivity between the fields were mainly caused by a loss of gross primary productivity in the Treatment field; ecosystem respiration was similar for both fields. When biomass removals and manure applications are included in the carbon budget, the Treatment field lost 149 g C M-2 whereas the Control field sequestered 96 g C m(-2), for a net difference of 245 g C M-2 over the June to December period (210 d). This suggests that perennial grass converted for annual cropping can lose more carbon than perennial grassland can sequester in a season.
  • Authors:
    • Lafond, G. P.
    • Schoenau, J. J.
    • Hangs, R. D.
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 176
  • Issue: 2
  • Year: 2013
  • Summary: With a world population now > 7 billion, it is imperative to conserve the arable land base, which is increasingly being leveraged by global demands for producing food, feed, fiber, fuel, and facilities (i.e., infra-structure needs). The objective of this study was to determine the effect of varying fertilizer-N rates on soil N availability, mineralization, and CO2 and N2O emissions of soils collected at adjacent locations with contrasting management histories: native prairie, short-term (10 y), and long-term (32 y) no-till continuous-cropping systems receiving five fertilizer-N rates (0, 30, 60, 90, and 120kg N ha1) for the previous 9 y on the same plots. Intact soil cores were collected from each site after snowmelt, maintained at field capacity, and incubated at 20 degrees C for 6 weeks. Weekly assessments of soil nutrient availability along with CO2 and N2O emissions were completed. There was no difference in cumulative soil N supply between the unfertilized long-term no-till and native prairie soils, while annual fertilizer-N additions of 120kg N ha1 were required to restore the N-supplying power of the short-term no-till soil to that of the undisturbed native prairie soil. The estimated cumulative CO2-C and N2O-N emissions among soils ranged from 231.8474.7 g m2 to 183.9862.5 mg m2, respectively. Highest CO2 fluxes from the native prairie soil are consistent with its high organic matter content, elevated microbial activity, and contributions from root respiration. Repeated applications of 60kg N ha1 resulted in greater residual inorganic-N levels in the long-term no-till soil, which supported larger N2O fluxes compared to the unfertilized control. The native prairie soil N2O emissions were equal to those from both short- and long-term no-till soils receiving repeated fertilizer-N applications at typical agronomic rates (e.g., 90kg N ha1). Eighty-eight percent of the native soil N2O flux was emitted during the first 2 weeks and is probably characteristic of rapid denitrification rates during the dormant vegetative period after snowmelt within temperate native grasslands. There was a strong correlation (R-2 0.64; p < 0.03) between measured soil Fe-supply rate and N2O flux, presumably due to anoxic microsites within soil aggregates resulting from increased microbial activity. The use of modern no-till continuous diversified cropping systems, along with application of fertilizer N, enhances the soil N-supplying power over the long-term through the build-up of mineralizable N and appears to be an effective management strategy for improving degraded soils, thus enhancing the productive capacity of agricultural ecosystems. However, accounting for N2O emissions concomitant with repeated fertilizer-N applications is imperative for properly assessing the net global warming potential of any land-management system.
  • Authors:
    • Stevenson, F. C.
    • Vanasse, A.
    • Legere, A.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 3
  • Year: 2013
  • Summary: Combining low-input systems with conservation tillage may be feasible for field crops under northeastern conditions. This study compared the effects of herbicide-free (HF), organic (ORG), conventional (CONV), and herbicide-tolerant (GM) cropping systems applied to three 20 yr-old tillage treatments (MP, moldboard plow; CP, chisel plow; NT, no-till) on weed biomass and crop productivity in a 4-yr barley ( Hordeum vulgare L.)-red clover ( Trifolium pratense L.)-corn ( Zea mays L.)-soybean [ Glycine max (L.) Merr.] rotation. Barley yield (4.5 Mg ha -1), and red clover forage yield (two cuts: 5.3 Mg ha -1) were similar across treatments. With MP and CP tillage, silage corn yield for CONV and GM systems (15 Mg ha -1) was 25% greater than for HF and ORG (11 Mg ha -1), whereas HF-NT and ORG-NT systems produced no harvestable yield. Soybean yield for HF-MP and ORG-MP systems was similar to that for CONV and GM (2.4 Mg ha -1), whereas yield in for the HF and ORG systems with CP and NT was half or less than for other treatments. Some form of primary tillage (CP or MP) was needed in corn and soybean to achieve adequate weed control and yield in the ORG and HF systems. Midseason weed proportion of total biomass was greater in the HF and ORG systems with CP and NT, and provided good yield prediction in corn ( R2=0.74) and soybean ( R2=0.84). Nutrient availability appeared adequate in corn following N 2-fixing red clover but limiting in NT and CP for soybean following corn. Improving crop sequence, fertilization, and weed management will be key to the adoption of low-input systems using conservation tillage practices in cool, humid climates.
  • Authors:
    • Chow, T. L.
    • Damboise, J.
    • Lantz, V. A.
    • Olale, E.
    • Ochuodho, T. O.
    • Meng, F.
    • Daigle, J. L.
    • Li, S.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 68
  • Issue: 5
  • Year: 2013
  • Summary: We investigated the effects of soil and water conservation practices on mean and variance of potato (Solanum tuberosum L.) yield across 267 fields in northwestern New Brunswick, Canada, from 1988 to 2010. A stochastic production function method was used to account for seven soil and water conservation practices in addition to farm inputs, potato varieties, technological change, site characteristics, and seasonal climate effects. Overall, soil and water conservation structures had mixed effects on potato yield.While spring tillage and terracing increased mean potato yield, grassed waterways, drainage, chisel plowing, and other practices had the opposite effect. Rock management did not impact mean potato yield. Most practices did not impact yield variance. While soil and water conservation practices can be effective farm management tools for maintaining soil fertility and enhancing potato yields, there are no one-size-fits-all prescriptions to enhance yield.
  • Authors:
    • Wang, H.
    • Desjardins, R.
    • Neilsen, D.
    • Huffman, T.
    • Gameda, S.
    • Jong, R. de
    • Qian, B. D.
    • McConkey, B.
  • Source: Canadian Journal of Soil Science
  • Volume: 93
  • Issue: 2
  • Year: 2013
  • Summary: The Canadian agricultural sector is facing the impacts of climate change. Future scenarios of agroclimatic change provide information for assessing climate change impacts and developing adaptation strategies. The goal of this study was to derive and compare agroclimatic indices based on current and projected future climate scenarios and to discuss the potential implications of climate change impacts on agricultural production and adaptation strategies in Canada. Downscaled daily climate scenarios, including maximum and minimum temperatures and precipitation for a future time period, 2040-2069, were generated using the stochastic weather generator AAFC-WG for Canadian agricultural regions on a 0.5° * 0.5° grid. Multiple climate scenarios were developed, based on the results of climate change simulations conducted using two global climate models - CGCM3 and HadGEM1 - forced by IPCC SRES greenhouse gas (GHG) emission scenarios A2, A1B and B1, as well as two regional climate models forced by the A2 emission scenario. The agroclimatic indices that estimate growing season start, end and length, as well as heat accumulations and moisture conditions during the growing season for three types of field crops, cool season, warm season and over-wintering crops, were used to represent agroclimatic conditions. Compared with the baseline period 1961-1990, growing seasons were projected to start earlier, on average 13 d earlier for cool season and over-wintering crops and 11 d earlier for warm season crops. The end of the growing season was projected on average to be 10 and 13 d later for over-wintering and warm season crops, respectively, but 11 d earlier for cool season crops because of the projected high summer temperatures. Two indices quantifying the heat accumulation during the growing season, effective growing degree days (EGDD) and crop heat units (CHU) indicated a notable increase in heat accumulation: on average, EGDD increased by 15, 55 and 34% for cool season, warm season and over-wintering crops, respectively. The magnitudes of the projected changes were highly dependent on the climate models, as well as on the GHG emission scenarios. Some contradictory projections were observed for moisture conditions based on precipitation deficit accumulated over the growing season. This confirmed that the uncertainties in climate projections were large, especially those related to precipitation, and such uncertainties should be taken into account in decision making when adaptation strategies are developed. Nevertheless, the projected changes in indices related to temperature were fairly consistent.
  • Authors:
    • Sheppard, S. C.
    • Bittman, S.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 171
  • Year: 2013
  • Summary: Manure nitrogen (N) includes what can be generalized as organic N, which includes undigested N from the feeds; ammoniacal and easily hydrolysable N, which includes urea and uric acid; and nitrate/nitrite species, which are the least abundant. From excretion to landspreading, the largest change in N concentration occurs because of volatilization of ammonia (NH 3) from the ammoniacal and easily hydrolysable fraction. This process can be highly dependent on manure management, and some management strategies such as manure injection are largely designed to decrease NH 3 loss. This paper utilizes recent models of NH 3 emission from beef, dairy, swine and poultry production to estimate the net organic and ammoniacal N content of manure in Canadian Ecoregions before and after land spreading. Confinement versus grazing for beef is a major factor for overall net manure N application, and slurry versus solid manure is next most important. There are distinct differences among Ecoregions in the proportions of organic and ammoniacal N, so that generic assumptions are not appropriate. The estimates are mapped for all of Canada based on 2006 animal census. Several best management practices (BMPs) are evaluated using recent costing information (dollars per kg of NH 3-N saved from emission). Relatively low-cost BMPs related to slurry manure applied nation-wide could save 16 Gg NH 3-N year -1 for an estimated cost of $13 M. Other low-cost BMPs could increase this to a saving of 79 Gg NH 3-N year -1 or 26% of present emissions.
  • Authors:
    • Campbell, C. A.
    • Desjardins, R. L.
    • Smith, W. N.
    • McConkey, B. G.
    • Shrestha, B. M.
    • Grant, B. B.
    • Miller, P. R.
  • Source: Canadian Journal of Soil Science
  • Volume: 93
  • Issue: 1
  • Year: 2013
  • Summary: There is uncertainty about how crop rotation and tillage affect soil organic C (SOC) on the Canadian prairies. We compared SOC amount and change (SOC) for one continuous crop and four 3-yr fallow-containing crop rotations under no-tillage (NT), and two fallow-containing crop rotations under minimum-tillage (MT), from 1995 to 2005 in semiarid southwestern Saskatchewan. After 11 yr, SOC (0- to 15-cm depth) was 0.2 Mg C ha -1 higher under continuous crop compared with fallow-containing systems. There were no significant differences in SOC and SOC among fallow-containing rotations or between MT and NT. Total C inputs were weakly ( R2=0.18) but significantly ( P<0.05) correlated to SOC, which changed by0.33 Mg C ha -1 for each Mg ha -1 C input above or below 2.4 Mg C ha -1 yr -1. Carbon inputs were typically less than this amount and SOC generally decreased over the experiment. Simulations of SOC with the Century model were consistent with our observations regarding SOC per unit of C input. There was slight loss of SOC for the above-average precipitation regime during the study. Simulations also supported our finding that SOC differences between crop mix and tillage systems may require several decades to become distinguishable in this semiarid climate with small and variable C inputs.
  • Authors:
    • Giltrap, D.
    • Hernandez-Ramirez, G.
    • Kim, D.-G.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 168
  • Issue: March
  • Year: 2013
  • Summary: Rising atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and associated climate change. It is often assumed that there is a linear relationship between nitrogen (N) input and direct N2O emission in managed ecosystems and, therefore, direct N2O emission for national greenhouse gas inventories use constant emission factors (EF). However, a growing body of studies shows that increases in direct N2O emission are related by a nonlinear relationship to increasing N input. We examined the dependency of direct N2O emission on N input using 26 published datasets where at least four different levels of N input had been applied. In 18 of these datasets the relationship of direct N2O emission to N input was nonlinear (exponential or hyperbolic) while the relationship was linear in four datasets. We also found that direct N2O EF remains constant or increases or decreases nonlinearly with changing N input. Studies show that direct N2O emissions increase abruptly at N input rates above plant uptake capacity. The remaining surplus N could serve as source of additional N2O production, and also indirectly promote N2O production by inhibiting biochemical N2O reduction. Accordingly, we propose a hypothetical relationship to conceptually describe in three steps the response of direct N2O emissions to increasing N input rates: (1) linear (N limited soil condition), (2) exponential, and (3) steady-state (carbon (C) limited soil condition). In this study, due to the limited availability of data, it was not possible to assess these hypothetical explanations fully. We recommend further comprehensive experimental examination and simulation using process-based models be conducted to address the issues reported in this review. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Marfo, J.
    • Man, R.
    • Dang, Q.-L.
    • Li, J.
  • Source: Forest Ecology and Management
  • Volume: 298
  • Issue: June
  • Year: 2013
  • Summary: CO2 elevation stimulates plant growth, which in turn demands more nutrients to sustain. Since the increase of demand for nitrogen (N), phosphorus (P) and potassium (K) may be in different proportions, the optimal N-P-K ratios at elevated [CO2] are likely different from those at the ambient [CO2]. This study investigated the effects of various N supply levels with constant and variable (constant P and K concentrations) N-P-K ratios under ambient and elevated [CO2] on black spruce (Picea mariana Mill. BSP) seedlings. One-year-old seedlings were exposed to two [CO2] (370 vs. 720 mu mol mol(-1)), two nutrient ratio regimes (constant vs. variable N/P/K ratios) and six N concentrations (10, 80, 150, 220, 290 and 360 mu mol mol(-1)) in four environmentally controlled greenhouses for 3.5 months. Growth response to N varied with [CO2] and N/P/K ratios: under the elevated [CO2], height growth increased with increasing N supply when P and K concentrations were kept constant across different N levels, but it only increased when increasing N from 10 to 150 mu mol mol(-1), and started to decline with further increase in N supply when N/P/K ratios were kept constant at different N levels; at the ambient [CO2], height growth was greatest at 150 mu mol mol(-1) N and was generally greater at 220-360 than at 10 and 80 mu mol mol(-1) N in both nutrient ratio treatments. The foliage to root ratio, shoot mass ratio and total biomass generally increased with increasing N supply but root mass ratio decreased. The smallest specific leaf area occurred at the lowest N supply when N/P/K ratios were kept constant but at 220 mu mol mol(-1) N when P and K concentrations were kept constant across different N supplies. The results of leaf nutrient concentrations suggest that the elevated [CO2] increased demand for N, P and K and the increase for N was greater than P and K, altering the relationship between growth and nitrogen supply. Under the elevated [CO2], high N supplies resulted in growth suppression by critical toxicity content only in the constant N/P/K ratios treatment but low N supplies led to growth suppression by critical deficiency content in both nutrient ratio treatments. At the ambient [CO2], in contrast, N/P/K ratio treatments did not affect growth suppression by critical deficiency or critical toxicity content. Because elevated CO2 causes unequal increases in N, P and K demands, N-P-K ratios should be considered when modeling plant growth responses to elevated CO2. (C) 2013 Elsevier B.V. All rights reserved.