19602015
  • Authors:
    • Nyachiro, J. M.
    • Salmon, D. F.
    • Beres, B. L.
    • Collier, G. R. S.
    • Bork, E. W.
    • Spaner, D. M.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 2
  • Year: 2013
  • Summary: Triticale (* Triticosecale Wittmack) is a minor cereal crop in Alberta which has recently garnered interest as a biofuel feedstock. Basic agronomic information is lacking for triticale cultivars released since 1990. Field experiments were initiated in 2010 and conducted for 2 yr at four sites in central and southern Alberta to compare the impact of cultivar selection, seeding date, and seeding rate on grain yield, grain quality, and other agronomic traits. Six triticale cultivars released between 1996 and 2011, and one Soft White Spring wheat cultivar ( Triticum aestivum L.) were evaluated over two seeding dates; one before and one after 15% of the total seasonal growing degree days (GDD; base=0°C) had elapsed. The cultivars were evaluated at seeding rates of 250, 375, and 500 seeds m -2. Older triticale cultivars had higher grain yields but lower grain quality than cultivars released after 2000. The triticale cultivars produced more grain than Soft White Spring wheat in five of seven environments; however, Soft White Spring wheat exhibited better grain quality than the triticales. Yield generally increased linearly with seeding rate but the highest return on investment was observed at 375 seeds m -2. Provided there was not an early frost, triticale seeded after 15% of the seasonal GDD had elapsed could produce grain yield similar to the earlier-seeded triticale. A sustainable management system for triticale includes modern cultivars, a seeding date that can accumulate 1750 GDD's before frost, and a sowing density of at least 375 seeds m -2.
  • Authors:
    • Ruane, A. C.
    • Oppenheimer, M.
    • Debats, S. R.
    • Bradley, B. A.
    • Beukes, H.
    • Estes, L. D.
    • Schulze, R.
    • Tadross, M.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 12
  • Year: 2013
  • Summary: Crop model-specific biases are a key uncertainty affecting our understanding of climate change impacts to agriculture. There is increasing research focus on intermodel variation, but comparisons between mechanistic (MMs) and empirical models (EMs) are rare despite both being used widely in this field. We combined MMs and EMs to project future (2055) changes in the potential distribution (suitability) and productivity of maize and spring wheat in South Africa under 18 downscaled climate scenarios (9 models run under 2 emissions scenarios). EMs projected larger yield losses or smaller gains than MMs. The EMs' median-projected maize and wheat yield changes were -3.6% and 6.2%, respectively, compared to 6.5% and 15.2% for the MM. The EM projected a 10% reduction in the potential maize growing area, where the MM projected a 9% gain. Both models showed increases in the potential spring wheat production region (EM=48%, MM=20%), but these results were more equivocal because both models (particularly the EM) substantially overestimated the extent of current suitability. The substantial water-use efficiency gains simulated by the MMs under elevated CO 2 accounted for much of the EM-MM difference, but EMs may have more accurately represented crop temperature sensitivities. Our results align with earlier studies showing that EMs may show larger climate change losses than MMs. Crop forecasting efforts should expand to include EM-MM comparisons to provide a fuller picture of crop-climate response uncertainties.
  • Authors:
    • Zechmeister-Boltenstern, S.
    • Stahr, K.
    • Zehetner, F.
    • Wimmer, B.
    • Kitzler, B.
    • Rempt, F.
    • Watzinger, A.
    • Anders, E.
    • Soja, G.
  • Source: Agricultural and Food Science
  • Volume: 22
  • Issue: 4
  • Year: 2013
  • Summary: Biochar application is a promising strategy for sequestering carbon in agricultural soils and for improving degraded soils. Nonetheless, contradictory and unsettled issues remain. This study investigates whether biochar influences the soil microbial biomass and community structure using phospholipid fatty acid (PLFA) analysis. We monitored the effects of four different types of biochar on the soil microbial communities in three temperate soils of Austria over several months. A greenhouse experiment and two field experiments were conducted. The biochar application did not significantly increase or decrease the microbial biomass. Only the addition of vineyard pruning biochar pyrolysed at 400 degrees C caused microbial biomass to increase in the greenhouse experiment. The biochar treatments however caused shifts in microbial communities (visualized by principal component analysis). We concluded that the shifts in the microbial community structure are an indirect rather than a direct effect and depend on soil conditions and nutrient status.
  • Authors:
    • Sanchez-Diaz, M.
    • Araus, J. L.
    • Irigoyen, J. J.
    • Jauregui, I.
    • Sanz-Saez, A.
    • Aranjuelo, I.
    • Erice, G.
  • Source: Journal of Experimental Botany
  • Volume: 64
  • Issue: 7
  • Year: 2013
  • Summary: The expansion of the worlds population requires the development of high production agriculture. For this purpose, it is essential to identify target points conditioning crop responsiveness to predicted [CO2]. The aim of this study was to determine the relevance of ear sink strength in leaf protein and metabolomic profiles and its implications in photosynthetic activity and yield of durum wheat plants exposed to elevated [CO2]. For this purpose, a genotype with high harvest index (HI) (Triticum durum var. Sula) and another with low HI (Triticum durum var. Blanqueta) were exposed to elevated [CO2] (700 mol mol(1) versus 400 mol mol(1) CO2) in CO2 greenhouses. The obtained data highlighted that elevated [CO2] only increased plant growth in the genotype with the largest HI; Sula. Gas exchange analyses revealed that although exposure to 700 mol mol(1) depleted Rubisco content, Sula was capable of increasing the light-saturated rate of CO2 assimilation (A(sat)) whereas, in Blanqueta, the carbohydrate imbalance induced the down-regulation of A(sat). The specific depletion of Rubisco in both genotypes under elevated [CO2], together with the enhancement of other proteins in the Calvin cycle, revealed that there was a redistribution of N from Rubisco towards RuBP regeneration. Moreover, the down-regulation of N, NO3, amino acid, and organic acid content, together with the depletion of proteins involved in amino acid synthesis that was detected in Blanqueta grown at 700 mol mol(1) CO2, revealed that inhibition of N assimilation was involved in the carbohydrate imbalance and consequently with the down-regulation of photosynthesis and growth in these plants.
  • Authors:
    • Priesack, E.
    • Palosuo, T.
    • Osborne, T. M.
    • Olesen, J. E.
    • O'Leary, G.
    • Nendel, C.
    • Kumar, S. Naresh
    • Mueller, C.
    • Kersebaum, K. C.
    • Izaurralde, R. C.
    • Ingwersen, J.
    • Hunt, L. A.
    • Hooker, J.
    • Heng, L.
    • Grant, R.
    • Goldberg, R.
    • Gayler, S.
    • Doltra, J.
    • Challinor, A. J.
    • Biernath, C.
    • Bertuzzi, P.
    • Angulo, C.
    • Aggarwal, P. K.
    • Martre, P.
    • Basso, B.
    • Brisson, N.
    • Cammarano, D.
    • Rotter, R. P.
    • Thorburn, P. J.
    • Boote, K. J.
    • Ruane, A. C.
    • Hatfield, J. L.
    • Jones, J. W.
    • Rosenzweig, C.
    • Ewert, F.
    • Asseng, S.
    • Ripoche, D.
    • Semenov, M. A.
    • Shcherbak, I.
    • Steduto, P.
    • Stoeckle, C.
    • Stratonovitch, P.
    • Streck, T.
    • Supit, I.
    • Tao, F.
    • Travasso, M.
    • Waha, K.
    • Wallach, D.
    • White, J. W.
    • Williams, J. R.
    • Wolf, J.
  • Source: Nature Climate Change
  • Volume: 3
  • Issue: 9
  • Year: 2013
  • Summary: Projections of climate change impacts on crop yields are inherently uncertain(1). Uncertainty is often quantified when projecting future greenhouse gas emissions and their influence on climate(2). However, multi-model uncertainty analysis of crop responses to climate change is rare because systematic and objective comparisons among process-based crop simulation models(1,3) are difficult(4). Here we present the largest standardized model intercomparison for climate change impacts so far. We found that individual crop models are able to simulate measured wheat grain yields accurately under a range of environments, particularly if the input information is sufficient. However, simulated climate change impacts vary across models owing to differences in model structures and parameter values. A greater proportion of the uncertainty in climate change impact projections was due to variations among crop models than to variations among downscaled general circulation models. Uncertainties in simulated impacts increased with CO2 concentrations and associated warming. These impact uncertainties can be reduced by improving temperature and CO2 relationships in models and better quantified through use of multi-model ensembles. Less uncertainty in describing how climate change may affect agricultural productivity will aid adaptation strategy development and policy making.
  • 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:
    • Blanco-Canqui, H.
  • Source: BioEnergy Research
  • Volume: 6
  • Issue: 1
  • Year: 2013
  • Summary: Crop residue removal for bioenergy can deplete soil organic carbon (SOC) pools. Management strategies to counteract the adverse effects of residue removal on SOC pools have not been, however, widely discussed. This paper reviews potential practices that can be used to offset the SOC lost with residue removal. Literature indicates that practices including no-till cover crops, manure and compost application, and return of biofuel co-products increase SOC pools and may thus be used to offset some SOC loss. No-till rotations that include semi-perennial grasses or legumes also offer a promise to promote soil-profile C sequestration and improve soil resilience after residue removal. No-till cover crops can sequester between 0.10 and 1 Mg ha(-1) per year of SOC relative to no-till without cover crops, depending on cover crop species, soil type, and precipitation input. Animal manure and compost contain about 15 % of C and thus their addition to soil can enhance SOC pools and boost soil biological activity. Similarly, application of biofuel co-products such as biochar, which contain between 45 % and 85 % of C depending on the feedstock source and processing method, can enhance long-term C sequestration. These mitigation strategies may maintain SOC pools under partial residue removal in no-till soils but are unlikely to replace all the SOC lost if residue is removed at excessive rates. More field research and modeling efforts are needed to assess the magnitude at which the different mitigation strategies can overcome SOC loss with crop residue removal.
  • Authors:
    • Chapman, S. C.
    • James, A. T.
    • Dreccer, M. F.
    • Bourgault, M.
  • Source: Functional Plant Biology
  • Volume: 40
  • Issue: 2
  • Year: 2013
  • Summary: Atmospheric CO2 levels have increased from similar to 280 ppm in the pre-industrial era to 391 ppm in 2012. High CO2 concentrations stimulate photosynthesis in C-3 plants such as wheat, but large variations have been reported in the literature in the response of yield and other traits to elevated CO2 (eCO(2)). Few studies have investigated genotypic variation within a species to address issues related to breeding for specific adaptation to eCO(2). The objective of this study was to determine the response to eCO(2) of 20 wheat lines which were chosen for their contrasting expression in tillering propensity, water soluble carbohydrate (WSC) accumulation in the stem, early vigour and transpiration efficiency. Experiments were performed in control environment chambers and in a glasshouse with CO2 levels controlled at either 420 ppm (local ambient) or 700 ppm (elevated). The results showed no indication of a differential response to eCO(2) for any of these lines and adaptive traits were expressed in a consistent manner in ambient and elevated CO2 environments. This implies that for these traits, breeders could expect consistent rankings in the future, assuming these results are validated under field conditions. Additional climate change impacts related to drought and high temperature are also expected to interact with these traits such that genotype rankings may differ from the unstressed condition.
  • Authors:
    • Wu, J.
    • Luo, Z. Z.
    • Wang, J.
    • Cai, L. Q.
    • Zhang, R. Z.
  • Source: Zhongguo Shengtai Nongye Xuebao / Chinese Journal of Eco-Agriculture
  • Volume: 21
  • Issue: 8
  • Year: 2013
  • Summary: This study analyzed the effects of different tillage conditions on greenhouse gas emissions of double sequence pea-wheat rotation fields during 2011. Three greenhouse gases (CO 2, N 2O and CH 4) emission were investigated under four tillage types [conventional tillage without straw mulching (T), no-tillage without straw mulching (NT), conventional tillage with straw mulching (TS) and no-tillage with straw mulching (NTS)]. The carbon dioxide analyzer and static chamber-gas chromatographic techniques were used to continuously measure and analyze the greenhouse gases fluxes. The results showed that double sequence pea-wheat rotation fields served not only as source of atmospheric CO 2, N 2O, but also as sink of atmospheric CH 4. Compared with T, NT retarded CO 2 emission. The three conservation tillage methods of NTS, NT and TS reduced N 2O emission but significantly increased CH 4 absorption. CO 2 and N 2O fluxes were significantly correlated with topsoil temperature ( R2=0.92** and 0.89**), soil temperature at the 5 cm soil depth ( R2=0.95** and 0.91**) and soil temperature at the 10 cm soil depth ( R2=0.77* and 0.62*). CH 4 fluxes were uncorrected with soil temperature at different soil depths. The correlation coefficients between CO 2 and soil water content, and CH 4 and soil water content at 0-5 cm soil layer were 0.69* and 0.72*, respectively. The correlation coefficient between CO 2 and soil water content at the 5-10 cm soil layer was 0.77* and that between CH 4, and soil water content at the 5-10 cm soil layer was 0.64*. CO 2, CH 4, fluxes were positively correlated with soil water content at the 10-30 cm soil layer. N 2O fluxes showed negative correlations with soil water content at different soil layers. The calculated global warming potential of the three greenhouse gases under the different tillage conditions showed that NT limited greenhouse gas flux, thereby reducing greenhouse effect.
  • Authors:
    • Zhang, Y.
    • Wu, L.
    • Wang, H.
    • Liu, L.
    • Huang, L.
    • Niu, Y.
    • Chai, R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 96
  • Issue: 1
  • Year: 2013
  • Summary: Proper management of synthetic nitrogen (N) fertilizer can reduce direct N2O emission from soil and indirect CO2 emission from production and transportation of synthetic N. In the late 1990s, the average application rates of synthetic N were 212, 207 and 207 kg ha(-1), respectively, for rice, wheat, and maize in China's croplands. But research suggests that the optimal synthetic N application rates for the main grain crops in China should be in the range of 110-150 kg ha(-1). Excessive application of synthetic N has undoubtedly resulted in massive emission of greenhouse gases. Therefore, optimizing N application rates for grain crops in China has a great potential for mitigating the emission of greenhouse gases. Nevertheless, this mitigation potential (MP) has not yet been well quantified. This study aimed at estimating the MP of N2O and CO2 emissions associated with synthetic N production and transportation in China based on the provincial level statistical data. Our research indicates that the total consumption of synthetic N on grain crops in China can be reduced by 5.0-8.4 Tg yr(-1) (28-47 % of the total consumption) if the synthetic N application rate is controlled at 110-150 kg ha(-1). The estimated total MP of greenhouse gases, including direct N2O emission from croplands and indirect CO2 emission from production and transportation of synthetic N, ranges from 41.7 to 70.1 Tg CO2_eq. yr(-1). It was concluded that reducing synthetic N application rate for grain crops in China to a reasonable level of 110-150 kg ha(-1) can greatly reduce the emission of greenhouse gases, especially in the major grain-crop production provinces such as Shandong, Henan, Jiangsu, Hebei, Anhui and Liaoning.