• Authors:
    • Asseng, S.
    • Zhu, Y.
    • Cao, W. X.
    • Tian, L. Y.
    • Liu, L. L.
    • Liu, B.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 2
  • Year: 2014
  • Summary: Wheat is sensitive to high temperatures, but the spatial and temporal variability of high temperature and its impact on yield are often not known. An analysis of historical climate and yield data was undertaken to characterize the spatial and temporal variability of heat stress between heading and maturity and its impact on wheat grain yield in China. Several heat stress indices were developed to quantify heat intensity, frequency, and duration between heading and maturity based on measured maximum temperature records of the last 50 years from 166 stations in the main wheat-growing region of China. Surprisingly, heat stress between heading and maturity was more severe in the generally cooler northern wheat-growing regions than the generally warmer southern regions of China, because of the delayed time of heading with low temperatures during the earlier growing season and the exposure of the post-heading phase into the warmer part of the year. Heat stress between heading and maturity has increased in the last decades in most of the main winter wheat production areas of China, but the rate was higher in the south than in the north. The correlation between measured grain yields and post-heading heat stress and average temperature were statistically significant in the entire wheat-producing region, and explained about 29% of the observed spatial and temporal yield variability. A heat stress index considering the duration and intensity of heat between heading and maturity was required to describe the correlation of heat stress and yield variability. Because heat stress is a major cause of yield loss and the number of heat events is projected to increase in the future, quantifying the future impact of heat stress on wheat production and developing appropriate adaptation and mitigation strategies are critical for developing food security policies in China and elsewhere.
  • Authors:
    • Cerri, C. C.
    • Bernoux, M.
    • Galdos, M. V.
    • Maia, Stoecio M. F.
    • Paustian, K.
    • Holbrook, N. M.
    • Davies, C. A.
    • Cerri, C. E. P.
    • Mello, F. F. C.
  • Source: Nature Climate Change
  • Volume: 4
  • Issue: 7
  • Year: 2014
  • Summary: Thee effects of land-use change (LUC) on soil carbon (C) balance has to be taken into account in calculating the CO2 savings attributed to bioenergy crops(1-3). There have been few direct fieldmeasurements that quantify thee effects of LUC on soil C for the most common land-use transitions into sugar cane in Brazil, the world's largest producer(1-3). We quantified the C balance for LUC as a net loss (carbon debt) or net gain (carbon credit) in soil C for sugar-cane expansion in Brazil. We sampled 135 field sites to 1 m depth, representing three major LUC scenarios. Our results demonstrate that soil C stocks decrease following LUC from native vegetation and pastures, and increase where cropland is converted to sugar cane. The payback time for the soil C debt was eight years for native vegetation and two to three years for pastures. With an increasing need for biofuels and the potential for Brazil to help meet global demand(4), our results will be invaluable for guiding expansion policies of sugar-cane production towards greater sustainability.
  • Authors:
    • Bui, E. N.
    • Webster, R.
    • Rossel, R. A. V.
    • Baldock, J. A.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 9
  • Year: 2014
  • Summary: We can effectively monitor soil condition - and develop sound policies to offset the emissions of greenhouse gases - only with accurate data from which to define baselines. Currently, estimates of soil organic C for countries or continents are either unavailable or largely uncertain because they are derived from sparse data, with large gaps over many areas of the Earth. Here, we derive spatially explicit estimates, and their uncertainty, of the distribution and stock of organic C in the soil of Australia. We assembled and harmonized data from several sources to produce the most comprehensive set of data on the current stock of organic C in soil of the continent. Using them, we have produced a fine spatial resolution baseline map of organic C at the continental scale. We describe how we made it by combining the bootstrap, a decision tree with piecewise regression on environmental variables and geostatistical modelling of residuals. Values of stock were predicted at the nodes of a 3-arc-sec (approximately 90 m) grid and mapped together with their uncertainties. We then calculated baselines of soil organic C storage over the whole of Australia, its states and territories, and regions that define bioclimatic zones, vegetation classes and land use. The average amount of organic C in Australian topsoil is estimated to be 29.7 t ha -1 with 95% confidence limits of 22.6 and 37.9 t ha -1. The total stock of organic C in the 0-30 cm layer of soil for the continent is 24.97 Gt with 95% confidence limits of 19.04 and 31.83 Gt. This represents approximately 3.5% of the total stock in the upper 30 cm of soil worldwide. Australia occupies 5.2% of the global land area, so the total organic C stock of Australian soil makes an important contribution to the global carbon cycle, and it provides a significant potential for sequestration. As the most reliable approximation of the stock of organic C in Australian soil in 2010, our estimates have important applications. They could support Australia's National Carbon Accounting System, help guide the formulation of policy around carbon offset schemes, improve Australia's carbon balances, serve to direct future sampling for inventory, guide the design of monitoring networks and provide a benchmark against which to assess the impact of changes in land cover, land management and climate on the stock of C in Australia. In this way, these estimates would help us to develop strategies to adapt and mitigate the effects of climate change.
  • Authors:
    • Sainju, U. M.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 4
  • Year: 2014
  • Summary: To determine farm C credit and reduce global warming potential, information is needed on the effect of management practices on soil C storage. The effects of tillage, cropping sequence, and N fertilization were evaluated on dryland crop biomass, surface residue C, and soil organic carbon (SOC) at the 0- to 120-cm depth in a Williams loam (fine-loamy, mixed, superactive, frigid, Typic Argiustolls) and their relationships with grain yields from 2006 to 2011 in eastern Montana. Treatments were no-till continuous malt barley ( Hordeum vulgare L.) (NTCB), no-till malt barley-pea ( Pisum sativum L.) (NTB-P), no-till malt barley-fallow (NTB-F), and conventional till malt barley-fallow (CTB-F), each with 0, 40, 80, and 120 kg N ha -1. Annualized crop grain and biomass yields, surface residue amount, and C contents were greater in NTB-P and NTCB than CTB-F and NTB-F and increased with increased N rates. At 0 to 5 and 5 to 10 cm, SOC was greater in NTB-P than CTB-F or NTCB with 40 kg N ha -1 and at 10 to 30 and 0 to 120 cm was greater in NTB-P than NTCB with 120 kg N ha -1. Surface residue C and SOC were related with grain yield and C content ( R2=0.21-0.55, P≤0.10, n=16). Greater amount of crop residue returned to the soil and turnover rate probably increased surface residue C, soil C storage, and crop yields in NTB-P with 40 and 120 kg N ha -1 than the other treatments. Soil organic matter and crop yields can be enhanced by using NTB-P with 40 kg N ha -1.
  • Authors:
    • Nalley, L. L.
    • Barkley, A.
    • Tack, J.
  • Source: Climatic Change
  • Volume: 125
  • Issue: 3-4
  • Year: 2014
  • Authors:
    • López-Solanilla, E.
    • Navas, M.
    • García-Marco, S.
    • Tellez-Rio, A.
    • Rees, R. M.
    • Tenorio, J. L.
    • Vallejo, A.
  • Source: Biology and Fertility of Soils
  • Volume: 51
  • Year: 2014
  • Summary: Lower greenhouse gas (GHG) emissions from legume-based cropping systems have encouraged their use to deliver mitigation in agricultural systems. Considerable uncertainties remain about the interaction of legumes with long-term tillage systems on GHG emissions under rainfed agroecosystems. In this context, a field experiment was undertaken under a rainfed vetch crop to evaluate the effect of three long-term tillage systems (i.e. no tillage (NT), minimum tillage (MT) and conventional tillage (CT)) on nitrous oxide (N2O) and methane (CH4) emissions for 1 year. Different N2O flux patterns were observed among tillage systems during the growth period of vetch, which depended on the soil conditions favouring nitrification and denitrification. The NT system maintained a higher sink for N2O than MT and CT from January to mid-April, which significantly reduced N2O emissions at this stage. In this period, denitrification capacity and nirK gene numbers were higher for MT than NT and CT. Additionally, an increase in soil NO 3 - content and more favourable denitrification conditions in MT and NT than in CT for the last crop period increased N2O emissions in conservation tillage systems. Total annual N2O losses were significantly higher in MT (124.2 g N2O-N ha-1) than NT (51.1 g N2O-N ha-1) and CT (54 g N2O-N ha-1) in a vetch crop. Low net uptake of CH4 was observed for all tillage systems. These results suggested that long-term NT may be a better option than MT to mitigate GHG emissions in rainfed legume-cereal rotation. © 2014 Springer-Verlag Berlin Heidelberg.
  • Authors:
    • McMahon, T. A.
    • Peel, M. C.
  • Source: Research Article
  • Volume: 38
  • Issue: 2
  • Year: 2014
  • Summary: Estimating evaporation from standard meteorological data continues to be an active area of research and practical application. Here we report on recent progress in using standard meteorology data to estimate potential, reference and actual evaporation from terrestrial landscapes as well as evaporation from lakes and reservoirs. We also address recent enhancements to standard methodologies through use of remote sensing and data-driven procedures. From our report we observe that remote sensing offers significant potential for mapping spatial variations in evaporation. There has been limited progress in estimating actual evaporation via the complementary relationship, whereas applications of the Penman-Monteith and related equations incorporating actual surface resistance term(s) have dominated the recent literature.
  • Authors:
    • Simmons, A.
    • Muir, S.
    • Brock, P.
  • Source: Conference Paper
  • Volume: 3
  • Year: 2014
  • Summary: Australian agricultural industries contribute approximately 14.6% of net annual national greenhouse gas (GHG) emissions, with N 2O emissions from agricultural soils the second greatest source of these emissions. Given that 25 M ha of land in Australia is cropped, the technical potential for GHG emissions reduction in Australian grain production systems is substantial. The New South Wales Department of Primary Industries (NSW DPI) has developed research capacity in Life Cycle Assessment (LCA) to assess this mitigation potential. In this paper we provide insights into the regionally-specific approach that we are taking, not only to provide credible management options at a grain grower level and ensure that detailed data are available for analysis by participants in the downstream supply chain, but also to provide data which, in an aggregated form, will underpin market access and inform national policy development. We report on initial NSW DPI studies and discuss a new project, funded by the Grains Research and Development Corporation (GRDC), to determine emissions reduction opportunities for each of Australia's agro-ecological zones. Initial studies show total emissions from wheat production in the order of 200 kg CO 2-e per tonne, with values ranging down to 140 kg CO 2-e per tonne. In one study, replacing synthetic nitrogenous fertiliser with biologically fixed N reduced emissions to 33% of prior values. The new project is particularly concerned with developing accurate foreground data by triangulating several sources of published literature (including official statistics) and conducting 'groundtruthing' through panels of regionally-based advisors to increase data specificity. The LCAs and associated mitigation strategies will be underpinned by a median and relevant distribution of values for inputs, practices and yields, with system assumptions clearly documented.
  • Authors:
    • Fisher,S.
    • Karunanithi,A.
  • Source: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector
  • Year: 2014
  • Summary: Local policy makers typically do not have useful, quantitative metrics to compare environmental costs and benefits of urban vegetable production versus the large-scale commercial production in the typical grocery store supply chain. While urban agriculture has been championed as a way to address social issues such as food access and nutrition, we know relatively little about net environmental benefits, if any. The study combines a comparative life cycle assessment of vegetables with effects of direct and indirect land use change resulting from the urban vegetable production. This paper presents a methodology and selected results of scenarios of land use change due to urban vegetable production address resource use, greenhouse gas emissions, employment, and soil organic carbon. Surprisingly, urban vegetable production is not categorically favorable for each metric; several key parameters can shift the balance in favor or out of favor for either growing format, and these parameters are distinctly bottom-up.
  • Authors:
    • Bathke, D. J
    • Oglesby, R. J.
    • Rowe, C. M.
    • Wilhite, D. A.
  • Year: 2014
  • Summary: The goal of this report is to inform policy makers, natural resource managers, and the public about the state of the science on climate change, current projections for ongoing changes over the twenty-first century, current and potential future impacts, and the management and policy implications of these changes. Hopefully, this report will lead to a higher degree of awareness and the initiation of timely and appropriate strategic actions that will enable Nebraskans to prepare for and adapt to future changes to our climate.