• Authors:
    • Gan, Y. T.
    • Cui, H. Y.
    • Yin, W.
    • Yu, A. Z.
    • Chai, Q.
    • Hu, F. L.
  • Source: AGRONOMY FOR SUSTAINABLE DEVELOPMENT
  • Volume: 35
  • Issue: 2
  • Year: 2015
  • Summary: Intercropping is used to increase grain production in many areas of the world. However, this increasing crop yield costs large amounts of water used by intercropped plants. In addition, intercropping usually requires higher inputs that induce greenhouse gas emissions. Actually, it is unknown whether intercropping can be effective in water-limited arid areas. Here, we measured crop yield, water consumption, soil respiration, and carbon emissions of wheat-maize intercropping under different tillage and crop residue management options. A field experiment was conducted at Wuwei in northwest China in 2011 and 2012. Our results show that wheat-maize intercropping increased grain yield by 61 % in 2011 and 63 % in 2012 compared with the average yield of monoculture crops. The intercropping under reduced tillage with stubble mulching yielded 15.9 t ha(-1) in 2011 and 15.5 t ha(-1) in 2012, an increase of 7.8 % in 2011 and 8.1 % in 2012, compared to conventional tillage. Wheat-maize intercropping had carbon emission of 2,400 kg C ha(-1) during the growing season, about 7 % less than monoculture maize, of 2,580 kg C ha(-1). Reduced tillage decreased C emission over conventional tillage by 6.7 % for the intercropping, 5.9 % for monoculture maize, and 7.1 % for monoculture wheat. Compared to monoculture maize, wheat-maize intercropping used more water but emitted 3.4 kg C per hectare per millimeter of water used, which was 23 % lower than monoculture maize. Overall, our findings show that maize-wheat intercropping with reduced tillage coupled with stubble mulching can be used to increase grain production while effectively lower carbon emissions in arid areas.
  • Authors:
    • Lemke, R. L.
    • Drury, C. F.
    • Smith, W. N.
    • Yang, J. Y.
    • Li, Z. T.
    • Grant, B.
    • He, W. T.
    • Li, X. G.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 3
  • Year: 2015
  • Summary: The overall performance of the Decision Support System for Agrotechnology Transfer-Cropping System Model (DSSAT-CSM) was evaluated for simulating wheat (Triticum aestivum L.) yield, grain N uptake, soil organic C (SOC) and N (SON), soil water and nitrate-N (NO3-N) dynamics. The data used was from a long-term (1967-2005) spring wheat experiment conducted at Swift Current, Saskatchewan in the semi-arid Canadian prairies. Four treatments were selected: (1) continuous wheat receiving N and P fertilizer, Cont-W(NP); (2) continuous wheat receiving P only, Cont-W(P); and each phase of a fallow wheat rotation receiving N and P fertilizer, (3) W-F(NP) and (4) F-W(NP). The simulated grain yields matched the measurements well, with high d (0.74-0.83) and EF (0.16-0.33). The grain N uptake was also simulated satisfactorily with RMSE of 14-17 kg N ha(-1) and d of 0.66-0.81. DSSAT simulated topsoil (0-0.15 m) SOC and SON well in the drier period (1967-1991), whereas it underestimated SOC in the more humid period (1991-2003). The DSSAT successfully simulated soil water and NO3-N dynamics in 0-0.15 m depth, whereas it overestimated soil water and NO3-N in the deep layers and consequently underestimated NO3-N leaching, suggesting that further improvements in soil water module should be made for the semi-arid climatic conditions in Canadian prairies. Sensitivity results showed that soil water content was sensitive to both lower soil water and upper drainage limits in this study. The performances of DSSAT model to yield and soil dynamics were comparable with other models.
  • Authors:
    • Gao XiaoPeng
    • Asgedom,H.
    • Tenuta,M.
    • Flaten,D. N.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: The effects of band placement of enhanced efficiency fertilizers (EEF) on nitrous oxide (N 2O) emissions are uncertain. Placement and EEF on N 2O emissions from spring wheat ( Triticum aestivum L.) at two locations in Manitoba, in 2011 and 2012 were examined. Treatments were a no N control and 80 kg N ha -1 at planting of five combinations of placement and granular N source: broadcast-incorporated urea (Urea I) and, subsurface side-banded urea (Urea S; each row side-banded), midrow-banded urea (Urea M; placement between every other set of rows), midrow-banded environmentally smart nitrogen (ESN, Agrium, Inc.) (ESN M), and midrow-banded SuperU (Koch Industries Inc.) (SuperU M). Planting in 2011 was delayed 40 d compared to 2012. Planting coincided with higher soil temperature and moisture resulting in three- to sevenfold more growing season N 2O emissions (SigmaN 2O) in 2011 than 2012. In 2011, SuperU M and ESN M reduced SigmaN 2O, emission factor (EF) scaled by N-applied EF, and yield-scaled N 2O emission intensity (EI) by 47, 67, and 55%, respectively, compared with Urea I. In 2011, increasing placement concentration of N in order broadcast-incorporation, side-banding, and midrow-banding tended to decrease SigmaN 2O, EF, and EI of granular urea, but not statistically significant. The SigmaN 2O and nitrate exposure (NE), were significantly correlated over the site-years, indicating N availability from treatments in part determined emissions. Grain yield and crop N uptake were unaffected by sources and placement. These results suggest for early season wet and warm conditions, EEF N sources can reduce emissions compared with granular urea. Further studies are required to clarify placement effects on N 2O emissions.
  • Authors:
    • Gizaw, Mesgana
    • Gan, Thian Yew
    • Kuo, Chun-Chao
  • Source: Article
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: Under the effect of climate change, warming likely means that there will be more water vapour in the atmosphere and extreme storms are expected to occur more frequently and with greater severity, resulting in municipal Intensity-Duration-Frequency (IDF) curves with higher intensities and shorter return periods. A regional climate model, MM5 (the Pennsylvania State University / National Center for Atmospheric Research numerical model), was set up in a one-way, three-domain nested framework to simulate future summer (May to August) precipitation of central Alberta. MM5 is forced with climate data of four Global Climate Models, CGCM3, ECHAM5, CCSM3, and MIROC3.2, for the baseline 1971-2000 and 2011-2100 based on the Special Report on Emissions Scenarios A2, A1B, and B1 of Intergovernmental Panel on Climate Change. Due to the bias of MM5's simulations, a quantile-quantile bias correction method and a regional frequency analysis is applied to derive projected grid-based IDF curves for central Alberta. In addition, future trends of air temperature and precipitable water, which affect storm pattern and intensity, are investigated. Future IDF curves show a wide range of increased intensities especially for storms of short durations (a parts per thousand currency sign1-h). Conversely, future IDF curves are expected to shift upward because of increased air temperature and precipitable water which are projected to be about 2.9 A degrees C and 29 % in average by 2071-2100, respectively. Our results imply that the impact of climate change could increase the future risk of flooding in central Alberta.
  • Authors:
    • Shirtliffe, S. J.
    • Banniza, S.
    • Syrovy, L. D.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Field pea ( Pisum sativum L.) is an important organic crop due to its contribution to soil fertility and other rotational benefits. Leafed (wild-type) pea cultivars tend to be more weed suppressive, but their poor standing ability limits yield compared with semi-leafless cultivars. Growing mixtures of leafed and semi-leafless cultivars may improve weed suppression and yield compared with monocultures of the same cultivars by altering canopy morphology. To test this hypothesis, replicated field experiments were conducted under weedy, organic conditions in Saskatchewan, Canada, in 2011 and 2012. Mixtures of a leafed and semi-leafless cultivar, CDC Sonata and CDC Dakota, were sown in ratios of 0:100, 25:75, 50:50, 75:25, and 100:0 leafed to semi-leafless pea, at target seeding rates of 88 and 132 plants m -2. Mixtures that included 50% or more semi-leafless pea had similar lodging resistance and weed biomass suppression to the agronomically superior semi-leafless cultivar grown alone. The strong competitive ability of the semi-leafless cultivar was unexpected based on previous accounts. The combined yield of the two cultivars grown in a 75% semi-leafless mixture exceeded the seed and biomass yield of either single cultivar by at least 18 and 12%, respectively. Yield enhancement was attributed to the leafed cultivar, whose seed yield increased by more than two and a half times in this mixture relative to its monoculture. Results suggest that breeding of leafed cultivars specifically for mixture with semi-leafless pea may be a future source of yield gains in organic and low-input systems.
  • Authors:
    • VandenBygaart, A. J.
    • Smith, W. N.
    • Campbell, C. A.
    • Grant, B. B.
    • Congreves, K. A.
    • Krobel, R.
    • Lemke, R. L.
    • Desjardins, R. L.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: Agricultural management practices which promote soil organic carbon (SOC) sequestration can contribute to the long-term productivity of soils, thus research must quantify and predict SOC dynamics in response to crop management. Using long-term (1967-2009) data from 10 cropping systems on a Brown Chernozem (Aridic Haploboroll) in the Canadian semiarid prairies at Swift Current, Saskatchewan, we assessed the effect of fertilizer, cropping frequency, and crop type on SOC dynamics in the 0- to 15-cm depth. Three models: Campbell, introductory carbon balance model (ICBM), and DayCent were evaluated, all of which produced fairly accurate predictions of SOC content and sequestration rates ( R2 of 0.64-0.82); however, DayCent had the highest correlation and lowest errors of prediction and was deemed superior. Residue inputs of 0.87 to 1.13 Mg C ha -1 yr -1 maintained the SOC level, and SOC content was directly related to factors which increased C inputs. The SOC content and sequestration rates were lowest for wheat ( Triticum aestivum L.)-based rotations which were frequently fallowed and included flax ( Linum usitatissimum L.), but highest for systems which were frequently cropped, well-fertilized, and included rye ( Secale cereale L.) or pulse crops in rotation. For systems with high C input, DayCent projected SOC gains of 12 Mg C ha -1 from 2009 to 2100, indicating that the soil at Swift Current had not reached maximum C capacity. This study was the first to rigorously test and demonstrate the strength of the DayCent for simulating SOC under different cropping systems on the Canadian prairies.
  • Authors:
    • Messerli,J.
    • Bertrand,A.
    • Bourassa,J.
    • Belanger,G.
    • Castonguay,Y.
    • Tremblay,G.
    • Baron,V.
    • Seguin,P.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: The increase in atmospheric carbon dioxide concentration ([CO 2]) and consequent increase in air temperature is expected to have significant effects on plant growth and nutritive value. Studies examining the effects of elevated [CO 2] on plants under field conditions have been limited by the inherent difficulty to modify air composition in open air. Here we describe an efficient and inexpensive open-top chamber (OTC) system designed to study the effects of elevated atmospheric [CO 2] and temperature on perennial alfalfa-timothy ( Medicago sativa L.)-( Phleum pratense L.) mixture. The design and construction of these OTCs are described in detail, along with cost estimation for each component. Eight OTCs, each with 1.2 m 2 of ground area (four with elevated [CO 2] and four with ambient [CO 2]) were fabricated and four control plots of the same dimension were established to assess the chamber effects on plant responses to CO 2. The [CO 2] in elevated-CO 2 chambers fell 93% of the time within 20% of the targeted 600 mol mol -1 CO 2, based on 10 min averages. The CO 2 consumption in elevated-CO 2 chambers averaged 3.0 kg CO 2 m -2 d -1. To ensure that the environment within OTCs was similar to the surrounding field, growing conditions were determined in all chambers and control plots. Adequate light transmission was observed compared to control plots (93%) and the temperature increase was 0.7°C on average. After two growing seasons of continued use, this system has proven its effectiveness for studying the effects of CO 2 and climate change in the field at low cost.
  • Authors:
    • Smith,E. G.
    • Janzen,H. H.
    • Larney,F. J.
  • Source: Canadian Journal of Soil Science
  • Volume: 95
  • Issue: 2
  • Year: 2015
  • Summary: Long-term cropping system studies offer insights into soil management effects on agricultural sustainability. In 1995, a 6-yr bioassay study was superimposed on a long-term crop rotation study established in 1951 at Lethbridge, Alberta, to determine the impact of past cropping systems on soil quality, crop productivity, grain quality, and the relationship of yield productivity to soil quality. All plots from 13 long-term crop rotations were seeded to wheat ( Triticum aestivum L.) in a strip plot design [control, nitrogen (N) fertilizer]. Prior to seeding, soils were sampled to determine soil chemical properties. Total wheat production for the last 4 yr of the study was used as the measure of productivity. The 1995 soil analysis indicated crop rotations with less frequent fallow and with N input had higher soil quality, as indicated by soil organic carbon (SOC) and light fraction carbon (LF-C) and N (LF-N). SOC had a positive relationship to total wheat yield, but was largely masked by the application of N in this bioassay study. Frequent fallow in the previous crop rotation lowered productivity. The concentration of LF-C had a negative relationship, whereas LF-N had a positive relationship to total wheat yield, with and without N fertilization in this bioassay study. Grain N concentration was higher with applied N and when the long-term rotation included the addition of N by fertilizer, livestock manure, annual legume green manure or legume hay. This study determined that long-term imposition of management practices have lasting effects on soil quality and crop productivity.
  • Authors:
    • Huffman,T.
    • Liu JianGui
    • McGovern,M.
    • McConkey,B.
    • Martin,T.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 205
  • Year: 2015
  • Summary: Accurate estimation of greenhouse gas emissions and detailed monitoring of the carbon cycle are important for mitigation of and adaptation to climate change. On agricultural land, annual herbaceous vegetation is not considered a carbon sink, whereas perennial woody vegetation accumulates biomass over multiple years and does represent a carbon sink. This paper presents a study to estimate aboveground woody carbon stock in 1990 and its annual change from 1990 to 2000 on Canada's cropland. The cropland was stratified into zones according to soils, climate and cropping systems, within which sample plots were randomly selected and paired aerial photographs corresponding to circa 1990 and 2000 were interpreted to detect changes in perennial woody vegetation such as trees, shrubs, orchards and vineyards. Woody biomass volumes lost as a result of land use change and gained as a result of planting and growth were estimated using species composition and growth rates typical of each zone, as obtained from published literature, forest reports and charts and forestry expert knowledge. Census of agriculture data was used to scale up the sample level results to zone and national levels. Results showed that on Canada's cropland, the aboveground woody carbon stock in 1990 was 33.78.8 Tg. Between 1990 and 2000, the area covered by woody vegetation was affected negatively by removals and positively through planting and natural regeneration, leading to a net reduction in area. There was an annual increase of about 78.3 Gg over all cropland in Canada, with a net decrease in some ecozones. Although this is a comparatively small increase with a large uncertainty, it indicates that changes in woody carbon on cropland in Canada over the 1990-2000 period were relatively insignificant. Further studies may be needed to refine the carbon estimates and reduce uncertainties.
  • Authors:
    • Vary,Z.
    • Mullins,E.
    • McElwain,J. C.
    • Doohan,F. M.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: Wheat diseases present a constant and evolving threat to food security. We have little understanding as to how increased atmospheric carbon dioxide levels will affect wheat diseases and thus the security of grain supply. Atmospheric CO 2 exceeded the 400 ppmv benchmark in 2013 and is predicted to double or even treble by the end of the century. This study investigated the impact of both pathogen and wheat acclimation to elevated CO 2 on the development of Fusarium head blight (FHB) and Septoria tritici blotch (STB) disease of wheat. Here, plants and pathogens were cultivated under either 390 or 780 ppmv CO 2 for a period (two wheat generations, multiple pathogen subcultures) prior to standard disease trials. Acclimation of pathogens and the wheat cultivar Remus to elevated CO 2 increased the severity of both STB and FHB diseases, relative to ambient conditions. The effect of CO 2 on disease development was greater for FHB than for STB. The highest FHB disease levels and associated yield losses were recorded for elevated CO 2-acclimated pathogen on elevated CO 2-acclimated wheat. When similar FHB experiments were conducted using the disease-resistant cultivar CM82036, pathogen acclimation significantly enhanced disease levels and yield loss under elevated CO 2 conditions, thereby indicating a reduction in the effectiveness of the defence pathways innate to this wheat cultivar. We conclude that acclimation to elevated CO 2 over the coming decades will have a significant influence on the outcome of plant-pathogen interactions and the durability of disease resistance.