• Authors:
    • Groffman, Peter M.
    • Gold, A. J.
    • Nowicki, B. L.
    • Kellogg, D. Q.
    • Addy, K.
    • Clough, T. J.
  • Source: Global Change Biology
  • Volume: 13
  • Issue: 7
  • Year: 2007
  • Summary: Few data are available to validate the Intergovernmental Panel on Climate Change's (IPCC) emission factors for indirect emissions of nitrous oxide (N2O). In particular the N2O emissions resulting from nitrogen leaching and the associated groundwater and surface drainage (EF5-g) are particularly poorly characterized. In situ push-pull methods have been used to identify the fate of NO3 in the groundwater. In this study, we adapted a previously published in situ denitrification push-pull method to examine the fate of 15N2O introduced into the subsoil-groundwater matrix. Enriched 15 N2O was manufactured, added to groundwater via a closed system in the laboratory, and then introduced into the groundwater-subsoil matrix in an upland-marsh transition zone of a salt marsh and a forested alluvial riparian zone. Conservative tracers (SF6 and Br ) and 15N2O were injected into the groundwater and left for 1-4 h after which the groundwater was sampled. Added 15N2O behaved in a conservative manner at one site while the other site showed variability with some injections showing significant consumption (38 [micro]g N2O-15 Nkg-1 soil day-1) of 15N2O. Our results show that the fate and dynamics of N2O in groundwater are complex and variable and that these dynamics should be considered in the development of improved IPCC inventory calculations.
  • Authors:
    • Alberta Agriculture and Food
  • Year: 2007
  • Authors:
    • Saarnio, S.
    • Penttilä, T.
    • Lohila, A.
    • Laurila, T.
    • Mäkiranta, P.
    • Hytönen, J.
    • Laine, J.
    • Silvan, N.
    • Aro, L.
    • Tuttila, E. -S.
    • Minkkinen, K.
    • Martikainen, P. J.
    • Maljanen, M.
    • Shurpali, N. J.
    • Alm, J.
  • Source: Boreal Environment Research
  • Volume: 12
  • Issue: 2
  • Year: 2007
  • Summary: This paper summarises the results of several research groups participating in the research programme "Greenhouse Impacts of the use of Peat and Peatlands in Finland", and presents emission factors for peat-atmosphere fluxes of CO2, CH4, and N2O, filling gaps in knowledge concerning the afforestation of organic croplands and cutaways, and improves the emission assessment of peatlands drained for forestry. Forest drainage may result in net binding of soil carbon or net release, depending on site characteristics and the tree stand. Use of peatlands for agriculture (48-4821 g CO2-eq. m(-2) a(-1)), even after the cultivation has ceased, or for milled peat harvesting (1948-2478 g CO2-eq. m(-2) a(-1)) can cause the highest overall emissions. Extremely high CO2 emissions are possible from peat harvesting areas during wet and warm summers. Afforestation of those peatlands abandoned from cultivation or peat harvesting can reduce the warming impact at least during the first tree generation. Heterotrophic soil respiration may have a systematic south-north difference in temperature response. More data must be collected before the information on peatland forest soil CO2 emissions can be adapted for different climatic regions in Finland. A test of the model DNDC against measured data showed that DNDC has to be developed further before it can be used in estimating N2O emissions from boreal peatlands.
  • Authors:
    • Ali, M. K.
    • Paustian, K.
    • Capalbo, S. M.
    • Antle, J. M.
  • Source: Climatic Change
  • Volume: 80
  • Issue: 1-2
  • Year: 2007
  • Summary: The purpose of this paper is to develop and apply a new method to assess economic potential for agricultural greenhouse gas mitigation. This method uses secondary economic data and conventional econometric production models, combined with estimates of soil carbon stocks derived from biophysical simulation models such as Century, to construct economic simulation models that estimate economic potential for carbon sequestration. Using this method, simulations for the central United States show that reduction in fallow and conservation tillage adoption in the wheat-pasture system could generate up to about 1.7 million MgC/yr, whereas increased adoption of conservation tillage in the corn-soy-feed system could generate up to about 6.2 million MgC/yr at a price of $200/MgC. About half of this potential could be achieved at relatively low carbon prices (in the range of $50 per ton). The model used in this analysis produced estimates of economic potential for soil carbon sequestration potential similar to results produced by much more data-intensive, field-scale models, suggesting that this simpler, aggregate modeling approach can produce credible estimates of soil carbon sequestration potential. Carbon rates were found to vary substantially over the region. Using average carbon rates for the region, the model produced carbon sequestration estimates within about 10% of those based on county-specific carbon rates, suggesting that effects of spatial heterogeneity in carbon rates may average out over a large region such as the central United States. However, the average carbon rates produced large prediction errors for individual counties, showing that estimates of carbon rates do need to be matched to the spatial scale of analysis. Transaction costs were found to have a potentially important impact on soil carbon supply at low carbon prices, particularly when carbon rates are low, but this effect diminishes as carbon prices increase.
  • Authors:
    • Lemke, R.
    • Malhi, S.
  • Source: Soil & Tillage Research
  • Volume: 96
  • Issue: 1/2
  • Year: 2007
  • Summary: An 8-yr (1998-2005) field experiment was conducted on a Gray Luvisol (Boralf) soil near Star City, Saskatchewan, Canada, to determine the effects of tillage (no-tillage - NT and conventional tillage - CT), straw management (straw retained - R and straw not retained - NR) and N fertilizer (0, 40, 80 and 120 kg N ha -1, except no N to pea ( Pisum sativum L.) phase of the rotation) on seed and straw yield, mass of N and C in crop, organic C and N, inorganic N and aggregation in soil, and nitrous oxide (N 2O) emissions for a second 4-yr rotation cycle (2002-2005). The plots were seeded to barley ( Hordeum vulgare L.) in 2002, pea in 2003, wheat ( Triticum aestivum L.) in 2004 and canola ( Brassica napus L.) in 2005. Seed, straw and chaff yield, root mass, and mass of N and C in crop increased with increasing N rate for barley in 2002, wheat in 2004 and canola in 2005. No-till produced greater seed (by 51%), straw (23%) and chaff (13%) yield of barley than CT in 2002, but seed yield for wheat in 2004, and seed and straw yield for canola in 2005 were greater under CT than NT. Straw retention increased seed (by 62%), straw (by 43%) and chaff (by 12%) yield, and root mass (by 11%) compared to straw removal for barley in 2002, wheat in 2004, and seed and straw yield for pea in 2003. No-till resulted in greater mass of N in seed, and mass of C in seed, straw, chaff and root than CT for barley in 2002, but mass of N and C were greater under CT than NT for wheat in 2004 and for canola in 2005 in many cases. Straw retention had greater mass of N and C in seed, straw, chaff and root in most cases compared to straw removal for barley in 2002, pea in 2003 and wheat in 2004. Soil moisture content in spring was higher under NT than CT and with R than NR in the 0-15 cm depth, with the highest moisture content in the NT + R treatment in many cases. After eight crop seasons, tillage and straw management had no effect on total organic C (TOC) and N (TON) in the 0-15 cm soil, but light fraction organic C (LFOC) and N (LFON), respectively, were greater by 1.275 Mg C ha -1 and 0.031 Mg N ha -1 with R than NR, and also greater by 0.563 Mg C ha -1 and 0.044 Mg N ha -1 under NT than CT. There was no effect of tillage, straw and N fertilization on the NH 4-N in soil in most cases, but R treatment had higher NO 3-N concentration in the 0-15 cm soil than NR. The NO 3-N concentration in the 0-15, 15-30 and 30-60 cm soil layers increased (though small) with increasing N rate. The R treatment had 6.7% lower proportion of fine (38.0 mm) dry aggregates, and 4.5 mm larger mean weight diameter (MWD) compared to NR treatment. This suggests a lower potential for soil erosion when crop residues are retained. There was no beneficial effect of elimination of tillage on soil aggregation. The amount of N lost as N 2O was higher from N-fertilized (580 g N ha -1) than from zero-N (155 g N ha -1) plots, and also higher in CT (398 g N ha -1) than NT (340 g N ha -1) in some cases. In conclusion, retaining crop residues along with no-tillage improved some soil properties and may also be better for the environment and the sustainability of high crop production. Nitrogen fertilization improved crop production and some soil quality attributes, but also increased the potential for NO 3-N leaching and N 2O-N emissions, especially when applied in excess of crop requirements.
  • Authors:
    • Salagean, D.
    • Oprea, G.
    • Pacurar, I.
  • Source: Analele Institutului National de Cercetare-Dezvoltare Agricola Fundulea
  • Volume: 75
  • Year: 2007
  • Summary: During 50 years (1957-2007), as part of NARDI Fundulea, Romania, studies and research on producing high quality seed, in small grains were performed. These investigations had as aim to improve the methodology and technology used in winter wheat and barley seed multiplication. Research regarding the variability of some traits in winter wheat and barley varieties during different periods, allowed their morphological and physiological characterization useful to maintain initial biological value of varieties during seed multiplication. Based on these studies, the seed multiplication schedule in small grains was established. Study regarding the influence of different seed biological categories on yielding capacity emphasized the fact that, during their multiplication, there is a slightly descendant tendency of this ability, but the yield diminutions became significant starting with the fourth multiplication of basic seed. The wheat crop fertilization under dryland and irrigation, with different nitrogen and phosphorus fertilizers demonstrated that, under both conditions, the application of some optimum rates favourably influenced the obtainment of seeds which lead to the yield increasing in the first year vs. fertilization with reduced rates. Harvesting of wheat and barley seed trials in three different stages (wax ripeness, full maturity and overmaturation) emphasized the fact that, the harvesting in optimum time (about 15% seed moisture) ensures the highest seed yields with superior quality indices. Study regarding the increasing of seed multiplication coefficient of new wheat and barley varieties to rapidly extend them into production emphasized the fact that, by using some reduced seed rates at sowing (about 25% of optimum seed rate), in the first two years after their registration, the seed multiplication coefficient increases from 1:20 to 1:80, four times respectively. Thus, the time for their extension into production could be reduced with two years minimum, with favourable economical effects.
  • Authors:
    • Lupwayi, N.
    • Haq, A.
    • Arshad, M.
    • Soon, Y.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1/2
  • Year: 2007
  • Summary: Information on which management practices can enhance soil organic matter (SOM) content and quality can be useful for developing sustainable crop production systems. We tested the influence of 12 years of no-till (NT) versus conventional tillage (CT), and four crop sequences on the organic C pools of a Grey Luvisolic sandy loam soil in northwestern Alberta, Canada. The crop sequences were: continuous wheat ( Triticum aestivum L.), field pea ( Pisum sativum L.)-wheat-canola ( Brassica rapa L.)-wheat, red clover ( Trifolium pratense L.) green manure-wheat-canola-wheat/red clover and fallow-wheat-canola-wheat. Soil samples from 1992, when the study was initiated, and 1996, 2000 and 2004 were analysed for total organic C (TOC), the light fraction (LF) and its C content, and water-soluble and mineralizable C. Total organic C in the top 15 cm of soil was higher in the red clover rotation than either the pea or fallow rotation by 1996. The tillage effect became significant only in 2004 with NT having a higher TOC than CT. The LF dry matter (DM) increased from 6.9 g kg -1 soil in 1992 to a range of 10-13 g kg -1 in 2000 and 2004. It was higher under NT than CT in 2 of 3 years and in the red clover rotation than the pea or fallow rotation in 1 of 3 years. The LF C content exhibited a similar trend as LF DM. The water-soluble and mineralizable C pools were not affected by tillage but decreased with time. Among crop rotations, the red clover rotation tended to result in higher levels of hot water-soluble and mineralizable C. It is concluded that tillage had a greater influence than crop rotation on the LF DM and LF C (as indicators of C storage), whereas the converse effect applied to mineralizable C and, to a lesser degree, hot water-soluble C (as indicators of SOM quality).
  • Authors:
    • Griffin, T. S.
    • Larkin, R. P.
  • Source: Crop Protection
  • Volume: 26
  • Issue: 7
  • Year: 2007
  • Summary: Brassica crops used in crop rotations and as green manures have been associated with reductions in soilborne pests and pathogens. These reductions have been attributed to the production of volatile sulfur compounds through a process known as biofumigation, and to changes in soil microbial community structure. In this study, selected Brassica crops, including canola, rapeseed, radish, turnip, yellow mustard, and Indian mustard, were evaluated for control of various soilborne potato pathogens and diseases in culture, in greenhouse trials, and in field trials on commercial potato farms. In in vitro assays, volatiles released from chopped leaf material of Brassica crops and barley inhibited growth of a variety of soilborne pathogens of potato, including Rhizoctonia solani, Phytophthora erythroseptica, Pythium ultimum, Sclerotinia sclerotiorum, and Fusarium sambucinam, with Indian mustard resulting in nearly complete inhibition (80-100%). All Brassica crops and barley reduced inoculum levels of R. solani (20-56% reduction) in greenhouse tests, and radish, rapeseed, and Indian mustard reduced subsequent potato seedling disease by 40-83%. In an on-farm field trial at a site with a substantial powdery scab problem, Indian mustard, rapeseed, canola, and ryegrass grown as green manure rotation crops reduced powdery scab in the subsequent potato crop by 15-40%, and canola and rapeseed reduced black scurf by 70-80% relative to a standard oats rotation. At another field site where common scab was the primary disease problem, an Indian mustard green manure reduced common scab by 25%, and rapeseed, yellow mustard, and 'Lemtal' ryegrass also reduced black scurf relative to a standard ryegrass rotation. Disease reductions were not always associated with higher glucosinolate-producing crops, and were also observed with non- Brassica crops (barley and ryegrass), indicating other mechanisms and interactions are important, particularly for control of R. solani. Overall, Indian mustard was most effective for reducing powdery scab and common scab diseases, whereas rapeseed and canola were most effective in reducing Rhizoctonia diseases. These results indicate that Brassica crops have potential for use as green manures for the control of multiple soilborne disease problems.
  • Authors:
    • Dosdall, L. M.
    • Moyer, J. R.
    • Clayton, G. W.
    • Harker, K. N.
    • Blackshaw, R. E.
    • O'Donovan, J. T.
    • Maurice, D. C.
    • Turkington, T. K.
  • Source: Crop Protection
  • Volume: 26
  • Issue: 3
  • Year: 2007
  • Summary: In western Canada, the move to integrated weed management (IWM) with reduced dependence on herbicides is being driven by low crop prices, weed resistance to herbicides, and environmental concerns. A rational step when implementing IWM is to determine if herbicide application is required in the first place. Crop yield loss models have been developed to assist with this decision. However, the weed economic threshold will be influenced considerably by management practices. Field studies showed that enhancing crop competitiveness through planting competitive varieties at relatively high seeding rates and through strategic fertilizer placement including sub-surface banded or point-injected nitrogen can reduce the impact of weeds on crop yield and the amount of weed seed entering the soil seed bank. Enhancing crop competitiveness also improved herbicide performance, especially when herbicides were applied at reduced doses. The inclusion of an early-cut silage crop in a rotation dramatically reduced wild oat ( Avena fatua L.) populations in barley ( Hordeum vulgare L.) while growing sweet clover ( Melilotus officinalis (L.) Lam) as a green manure in rotation with cereal and oilseed crops showed tremendous potential to suppress weeds. Other studies demonstrated that weed management should not be considered in isolation since it can influence the severity of alternative pests, for example, damage due to Delia spp. in canola ( Brassica napus L.). Further studies are required to examine the cumulative long-term effects of integrating the various weed management practices on all components of the crop ecosystem including weeds, diseases and insects.
  • Authors:
    • Holm, F. A.
    • Sapsford, K. L.
    • Cathcart, J.
    • Hall, L. M.
    • Clayton, G. W.
    • Harker, K. N.
    • O'Donovan, J. T.
    • Hacault, K.
  • Source: Weed Science
  • Volume: 55
  • Issue: 1
  • Year: 2007
  • Summary: There is no published information on the impact of volunteer barley on wheat yield loss or on the economics of controlling barley with a herbicide. With the registration of imazamox-resistant wheat, it is now possible to control volunteer barley in wheat. Thus, the likelihood of growing wheat in rotation with barley may increase. Field experiments were conducted in 2003 and 2004 at Beaverlodge, Lacombe, and Edmonton, AB, Canada, and Saskatoon, SK, Canada, to determine the impact of volunteer barley on yield of imazamox-resistant spring wheat seeded at relatively low (100 kg ha(-1)) and high (175 kg ha(-1)) rates. Barley was seeded at different densities to simulate volunteer barley infestations. Regression analysis indicated that wheat-plant density influenced the effects of volunteer barley interference on wheat yield loss, economic threshold values, and volunteer barley fecundity among locations and years. Econornic thresholds varied from as few volunteer barley plants as 3 m(-2) at Beaverlodge in 2003 and 2004 to 48 m(-2) at Lacombe in 2003. In most cases, wheat yield loss and volunteer barley fecundity were lower and economic thresholds were higher when wheat was seeded at the higher rate. For example, averaged over both years at Beaverlodge initial slope values (percentage of wheat yield loss at low barley density) were 4.5 and 1.7%, and economic threshold values of volunteer barley plants were 3 m(-2) and 8 m(-2) at low and high wheat seeding rates, respectively. Results indicate that volunteer barley can be highly competitive in wheat, but yield losses and wheat seed contamination due to volunteer barley can be alleviated by seeding wheat at a relatively high rate.