• Authors:
    • Newnes, L.
    • Borrion, A. L.
    • Whittaker, C.
    • McManus, M.
  • Source: APPLIED ENERGY
  • Volume: 122
  • Year: 2014
  • Summary: The Renewable Energy Directive (RED) specifies that biomass feedstocks must be sustainable and are not directly implicated with conversion of areas of high carbon stock and biodiversity. There are concerns that first generation biofuels from food-based crops will lead to negative indirect impacts on food prices and place pressure on agricultural land. The RED incentivises the use of non-food and land biomass resources by awarding them with financial credits and assigning them a zero greenhouse gas (GHG) 'cost'. This paper questions whether there are any GHG implications with straw removal from soil that should be accounted for in the life cycle assessment (LCA) of straw-based bioethanol. Emission savings of 21-58% are calculated for straw-bioethanol compared to conventional fossil fuels. The direct GHG implications of straw removal from soil are highly dependent on assumptions on the changes in soil organic carbon (SOC) experienced during straw removal, as well as replacing nutrients removed in straw. The results show that these impacts have the potential to reduce the GHG emission savings to -133%. If straw was alternatively incorporated into the soil, this could sequester between 0.58 and 2.24 tonnes CO 2 eq./ha, whereas substitution of fossil fuels would avoid 0.46 and 1.16 tonnes CO 2 eq./ha, although the full accountable benefit of straw removal is questionable as it is easily reversible. Understanding the full implications of straw removal on GHG emissions relies on further research on residue removal limitations, the impact that losses of SOC has on soil quality, as well as determining whether straw will be acquired from increased removal from soil or displacement from existing markets.
  • Authors:
    • Lv, Y. Z.
    • Huang, F.
    • Zhao, N.
    • Yang, Z. C.
  • Source: SOIL & TILLAGE RESEARCH
  • Year: 2014
  • Summary: The aim of the study is to analyze the effects of different fertilization of organic and inorganic fertilizers on soil organic carbon (SOC) sequestration and crop yields after a 22 years long-term field experiment. The crop yields and SOC were investigated from 1981 to 2003 in Dry-Land Farming Research Institute of Hebei Academy of Agricultural and Forestry Sciences, Hebei Province, China. The dominant cropping systems are winter wheat-summer corn rotation. There were totally sixteen treatments applied to both wheat and corn seasons: inorganic fertilizers as main plots and corn stalks as subplots and the main plots and subplots all have four levels. The results revealed: after 22 years, mixed application of inorganic fertilizers and crop residuals, the SOC and crop yields substantially increased. Higher fertilizer application rates resulted in greater crop yields improvement. In 2002-2003, wheat and corn for the highest fertilizer inputs had the highest yield level, 6400 kg ha-1 and 8600 kg ha-1, respectively. However, the SOC decreased as the excessive inorganic fertilizer input and increased with the rising application of corn stalks. The treatment of the second-highest inorganic fertilizer and the highest corn stalks had the highest SOC concentration (8.64 g C kg-1). Pearson correlation analysis shows that corn and winter wheat yields and the mineralization amount of SOC have significant correlation with SOC at p < 0.05 level.
  • Authors:
    • Herridge, D.
    • Guppy, C.
    • Begum, N.
    • Schwenke, G.
  • Source: Biology and Fertility of Soils
  • Volume: 50
  • Issue: 3
  • Year: 2014
  • Summary: Few studies have compared emissions of nitrous oxide (N2O), the potent greenhouse gas associated with decomposition of both below-ground (root) and above-ground (shoot) residues. We report a laboratory incubation experiment to evaluate effects of root and shoot residues from wheat, canola, soybean, and sorghum, incorporated into a naturally fertile acidic Black Vertisol, on N2O and carbon dioxide (CO2) emissions. The residue-amended Vertisol samples were incubated at 25 A degrees C and 70 % water-filled pore space (WFPS) to facilitate denitrification activity for a total period of 56 days. The incubated soils were periodically sampled for N2O, CO2, mineral N, and dissolved organic carbon (DOC). In general, shoot residues emitted more CO2 than roots, while N2O emissions were 50-70 % higher in cereal root residues than those in shoots. Surprisingly, the highest N2O emissions were associated with soils amended with the more inert high C/N ratio residues (wheat and sorghum roots), and to some extent, lowest emissions were associated with low C/N ratio (more labile) residues, particularly during the early stages of incubation (0-22 days). During this stage, there was a significant (p < 0.01) and negative correlation between N2O emissions and microbial respiration (CO2 efflux) and a positive (p < 0.001) correlation between microbial respiration and DOC. These results suggest that residue decomposition linked to N immobilization reduced N2O emissions during this early stage. Only, later in the study (23-56 days), did the high %N, low C/N ratio residues of soybean shoot and canola roots release at least twice as much N2O as the majority of the other treatments. We concluded that the unexpected patterns of N2O emissions were a result of the initially high mineral N content of the incubated soils and that root residues are likely to contribute substantially to emissions from cropping soils.
  • Authors:
    • Silva, E. de O.
    • de Carvalho, C. A. C.
    • Bezerra, M. A.
  • Source: Revista Caatinga
  • Volume: 27
  • Issue: 1
  • Year: 2014
  • Summary: Over the past few years, the increased use of fossil fuels as well as the unsustainable use of land, through the reduction of native forests has increased the greenhouse gas emissions, contributing definitively to the rise in temperature on earth. In this scenario, two environmental factors, directly related to the physiology of crop production, are constantly being changed. The first change is the increase in the partial pressure of carbon dioxide (CO 2), which directly affects photosynthetic efficiency and the associated metabolic processes. The other change is the temperature increase which affects all the physiological and metabolic processes mediated by enzymes, especially photosynthesis and respiration. Therefore, this review aims to discuss the main effects caused by increased CO 2 pressure and the temperature rise in the physiology, productivity and post-harvest quality of plants with photosynthetic metabolism C3, C4 and CAM. Based on physiological evidence, the increased atmospheric CO 2 concentration will benefit net photosynthesis, stomatal conductance and the transpiration of C3 plants, however in hot, dry and saline environments, the C4 and CAM species present an advantage by having low photorespiration. Studies show controversial conclusions about the productivity of C3 and C4 plants, and the quality of their fruits or grains under different CO 2 concentrations or high temperatures. Thus, there is a need for more testing with C3 and C4 plants, besides of more research with CAM plants, in view of the low number of experiments carried out in this type of plants.
  • Authors:
    • Deng, J.
    • Zhou, Z.
    • Wang, K.
    • Liu, C.
    • Zheng, X.
    • Cui, F.
  • Source: Biogeosciences Discussions
  • Volume: 10
  • Year: 2014
  • Summary: Contemporary agriculture is shifting from a single-goal to a multi-goal strategy, which in turn requires choosing best management practice (BMP) based on an assessment of the biogeochemical effects of management alternatives. The bottleneck is the capacity of predicting the simultaneous effects of different management practice scenarios on multiple goals and choosing BMP among scenarios. The denitrification-decomposition (DNDC) model may provide an opportunity to solve this problem. We validated the DNDC model (version 95) using the observations of soil moisture and temperature, crop yields, aboveground biomass and fluxes of net ecosystem exchange of carbon dioxide, methane, nitrous oxide (N2O), nitric oxide (NO) and ammonia (NH3) from a wheat-maize cropping site in northern China. The model performed well for these variables. Then we used this model to simulate the effects of management practices on the goal variables of crop yields, NO emission, nitrate leaching, NH3 volatilization and net emission of greenhouse gases in the ecosystem (NEGE). Results showed that no-till and straw-incorporated practices had beneficial effects on crop yields and NEGE. Use of nitrification inhibitors decreased nitrate leaching and N2O and NO emissions, but they significantly increased NH3 volatilization. Irrigation based on crop demand significantly increased crop yield and decreased nitrate leaching and NH3 volatilization. Crop yields were hardly decreased if nitrogen dose was reduced by 15% or irrigation water amount was reduced by 25 %. Two methods were used to identify BMP and resulted in the same BMP, which adopted the current crop cultivar, field operation schedules and full straw incorporation and applied nitrogen and irrigation water at 15 and 25% lower rates, respectively, than the current use. Our study indicates that the DNDC model can be used as a tool to assess biogeochemical effects of management alternatives and identify BMP.
  • Authors:
    • Zhang, F. S.
    • Chen, X. P.
    • Ma, W. Q.
    • Ye, Y. L.
    • Wu, L.
    • Cui, Z. L.
  • Source: Biogeosciences
  • Volume: 11
  • Issue: 8
  • Year: 2014
  • Summary: Although the concept of producing higher yields with reduced greenhouse gas (GHG) emissions is a goal that attracts increasing public and scientific attention, the tradeoff between high yields and GHG emissions in intensive agricultural production is not well understood. Here, we hypothesize that there exists a mechanistic relationship between wheat grain yield and GHG emission, and that could be transformed into better agronomic management. A total 33 sites of on-farm experiments were investigated to evaluate the relationship between grain yield and GHG emissions using two systems (conventional practice, CP; high-yielding systems, HY) of intensive winter wheat (Triticum aestivum L.) in China. Furthermore, we discussed the potential to produce higher yields with lower GHG emissions based on a survey of 2938 farmers. Compared to the CP system, grain yield was 39% (2352 kg ha(-1)) higher in the HY system, while GHG emissions increased by only 10%, and GHG emission intensity was reduced by 21%. The current intensive winter wheat system with farmers' practice had a median yield and maximum GHG emission rate of 6050 kg ha(-1) and 4783 kg CO2 eq ha(-1), respectively; however, this system can be transformed to maintain yields while reducing GHG emissions by 26% (6077 kg ha(-1), and 3555 kg CO2 eq ha(-1)). Further, the HY system was found to increase grain yield by 39% with a simultaneous reduction in GHG emissions by 18% (8429 kg ha(-1), and 3905 kg CO2 eq ha(-1), respectively). In the future, we suggest moving the trade-off relationships and calculations from grain yield and GHG emissions to new measures of productivity and environmental protection using innovative management technologies.
  • Authors:
    • Olalde-Portugal, V.
    • Luna-Guido, M.
    • Hernandez-Valdez, E.
    • Manuel Ruiz-Valdiviezo, V.
    • del Rosario Cardenas-Aquino, M.
    • Aguilar-Chavez, A.
    • Diaz-Rojas, M.
    • Dendooven, L.
  • Source: Applied Soil Ecology
  • Volume: 73
  • Year: 2014
  • Summary: Agriculture is an important source of greenhouse gases (GHG), mostly carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). Application of charcoal to agricultural soils is known to reduce GHG emissions while application of fertilizer or wastewater sludge increases them. Therefore, the objective of this work was to study the effect of charcoal application on GHG emissions from soil planted with wheat (Triticum aestivum L.) and amended with wastewater sludge or urea, or left unamended. Wheat fertilized with urea or wastewater sludge, at a rate of 150 kg N ha(-1), was cultivated in soil amended with or without 2% (w/w) charcoal, a biochar used mostly for heating, in a greenhouse. Emission of CO2, CH4 and N2O, soil characteristics and plant development were monitored. Charcoal had no significant effect on the emission of CO2, CH4 and N2O in wastewater sludge or urea-amended soil. The wheat development and yields, and soil pH and electrolytic conductivity were also not affected by charcoal application. It was found that charcoal did not affect the emissions of the monitored GHG, wheat or soil characteristics. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Khan, N.
    • Samad, G.
    • Janjua, P.
  • Source: Njas-Wageningen Journal of Life Sciences
  • Volume: 68
  • Year: 2014
  • Summary: Climate change and its impact on agricultural production is being debated in economic literature in context of different regions. The geographical location of Pakistan is assumed to be vulnerable to climate change. Concentration of greenhouse gases (GHGs) like carbon dioxide, methane and nitrous oxide through human activities has altered the composition of climate. These gases have increased temperature on earth by trapping sun light. This higher temperature in tropical regions may negatively affect the growth process and productivity of wheat. This study aims to look at the impact of climate change on wheat production in Pakistan. The study uses Autoregressive Distributed Lag (ARDL) model to evaluate the impact of global climate change on the production of wheat in Pakistan. The study considers annual data from 1960 to 2009. On the basis of this historical data the study tries to capture the impact of climate change on wheat production up to now. The results of estimation reveal that global climate change doesn't influence the wheat production in Pakistan. However, on the basis of the results some appropriate adaptative measures are proposed to confront any adverse shock to wheat production in Pakistan. (C) 2013 Royal Netherlands Society for Agricultural Sciences. Published by Elsevier B.V. All rights reserved,
  • Authors:
    • Rebetzke, G. J.
    • Watt, M.
    • Kirkby, C. A.
    • Hunt, J. R.
    • Conyers, M. K.
    • Kirkegaard, J. A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 187
  • Issue: April
  • Year: 2014
  • Summary: Adoption of conservation agriculture (CA) principles in Australia increased rapidly during the 1990s and it now boasts the highest adoption rates worldwide. These principles of (1) diverse rotations (2) reduced (or no-) till systems and (3) the maintenance of surface cover make good sense in extensive, mechanised, rain-fed cropping systems on erosion-prone, structurally-unstable soils. Indeed reduced fuel and labour costs, soil conservation and moisture retention are the most commonly stated reasons for adoption of CA principles by farmers in Australia. Yet even in Australia, while broadly applicable, the adaptation and application of CA principles within specific farming systems remains pragmatic due to the diverse biophysical and socio-economic factors encountered. Most "no-till" adopters continue some strategic tillage (similar to 30% cropped area) for a range of sound agronomic reasons, intensive cereal systems dominate, and partial removal of crop residues as hay or by grazing livestock is commonplace within the largely mixed-farming systems. Although this challenges the notion of "ideal" CA principles (zero-till with no soil disturbance, full stubble retention and >3 species in rotations) this high degree of flexibility in CA principles as practiced in southern Australian mixed farming systems makes sense to optimize both economic and environmental outcomes. In addition, some proposed ecosystem service benefits of CA such as soil carbon sequestration and energy efficiency have been recently questioned. Though the socio-economic factors of small-holder farming systems in Africa and south Asia are more diverse and clearly different to Australian farms, some of the biophysical challenges and economic realities are shared (infertile soils, variable and extreme climates, relatively low input levels, integrated crop-livestock systems, small profit margins, highly variable income). It is therefore useful to consider from a biophysical standpoint why a pragmatic approach to CA principles has been necessary, even in a relatively high-adopting country like Australia, and why we should expect similarly 'imperfect' adoption of CA (if at all) in the diverse smallholder systems of Sub-Saharan Africa and South Asia. We review aspects of CA adoption in Australia in an effort to draw out important lessons as CA principles are adapted elsewhere, including the smallholder farming systems of Sub-Saharan Africa and South Asia. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Hermansen, J. E.
    • Chirinda, N.
    • Olesen, J. E.
    • Meyer-Aurich, A.
    • Knudsen, M. T.
  • Source: Journal of Cleaner Production
  • Volume: 64
  • Issue: February
  • Year: 2014
  • Summary: Many current organic arable agriculture systems are challenged by a dependency on imported livestock manure from conventional agriculture. At the same time organic agriculture aims at being climate friendly. A life cycle assessment is used in this paper to compare the carbon footprints of different organic arable crop rotations with different sources of N supply. Data from long-term field experiments at three different locations in Denmark were used to analyse three different organic cropping systems ('Slurry', 'Biogas' and 'Mulching'), one conventional cropping system ('Conventional') and a "No input" system as reference systems. The 'Slurry' and 'Conventional' rotations received slurry and mineral fertilizer, respectively, whereas the 'No input' was unfertilized. The 'Mulching' and 'Biogas' rotations had one year of grass-clover instead of a faba bean crop. The grass-clover biomass was incorporated in the soil in the 'Mulching' rotation and removed and used for biogas production in the 'Biogas' rotation (and residues from biogas production were simulated to be returned to the field). A method was suggested for allocating effects of fertility building crops in life cycle assessments. The results showed significantly lower carbon footprint of the crops from the 'Biogas' rotation (assuming that biogas replaces fossil gas) whereas the remaining crop rotations had comparable carbon footprints per kg cash crop. The study showed considerable contributions caused by the green manure crop (grass-clover) and highlights the importance of analysing the whole crop rotation and including soil carbon changes when estimating carbon footprints of organic crops especially where green manure crops are included. (C) 2013 Elsevier Ltd. All rights reserved.