71. Nitrate leaching and residual effect in dairy crop rotations with grass-clover leys as influenced by sward age, grazing, cutting and fertilizer regimes.

• Authors:
  • Soegaard, K.
  • Rasmussen, J.
  • Askegaard, M.
  • Eriksen, J.
• Source: Agriculture, Ecosystems & Environment
• Volume: 212
• Year: 2015
• Summary: Intensive dairy farming, with grass-arable crop rotations is challenged by low N use efficiency that may have adverse environmental consequences. We investigated nitrate leaching and N fertility effects of grass-clover leys for five years in two organic crop rotations with different grassland proportions (33 and 67%) and five grassland managements in terms of cutting, grazing, fertilization and combinations thereof. In grass-clover, the combination of fertilization and grazing caused excessive leaching (average 60 kg N ha -1) but leaving out either fertilization or full-time grazing substantially reduced leaching losses to on average 23 kg N ha -1. There was no linear relationship between sward age and nitrate leaching. The annual N surplus of the grasslands was only weakly related to nitrate leaching ( R2=0.05, P50 kg N ha -1) with lupin and maize, where especially maize was consistently high in all five years (average 81 kg N ha -1). Great care should be taken during all phases of the dairy crop rotation where grasslands cause considerable build-up of fertility. With due care and the best management practice, nitrate leaching losses may be reduced to low levels.

72. The value of adapting to climate change in Australian wheat farm systems: farm to cross-regional scale.

• Authors:
  • Howden, M.
  • Chapman, S.
  • Zheng, B.
  • Moore, A.
  • Kokic, P.
  • Ghahramani, A.
  • Crimp, S.
• Source: Agriculture, Ecosystems & Environment
• Volume: 211
• Issue: December 2015
• Year: 2015
• Summary: Wheat is one of the main grains produced across the globe and wheat yields are sensitive to changes in climate. Australia is a major exporter of wheat, and variations in its national production influence trade supplies and global markets. We evaluated the effect of climate change in 2030 compared to a baseline period (1980-1999) by upscaling from farm to the national level. Wheat yields and gross margins under current and projected climates were assessed using current technology and management practices and then compared with 'best adapted' yield achieved by adjustments to planting date, nitrogen fertilizer, and available cultivars for each region. For the baseline climate (1980-1999), there was a potential yield gap modelled as optimized adaptation gave potential up scaled yields (tonne/ha) and gross margins (AUD$/ha) of 17% and 33% above the baseline, respectively. In 2030 and at Australian wheatbelt level, climate change impact projected to decline wheat yield by 1%. For 2030, national wheat yields were simulated to decrease yields by 1% when using existing technology and practices but increase them by 18% assuming optimal adaptation. Hence, nationally at 2030 for a fully-adapted wheat system, yield increased by 1% and gross margin by 0.3% compared to the fully adapted current climate baseline. However, there was substantial regional variation with median yields and gross margins decreasing in 55% of sites. Full adaptation of farm systems under current climate is not expected, and so this will remain an on-going challenge. However, by 2030 there will be a greater opportunity to increase the overall water use and nitrogen efficiencies of the Australian wheat belt, mostly resulting from elevated atmospheric CO 2 concentrations.

73. Assessing the combined use of reduced tillage and cover crops for mitigating greenhouse gas emissions from arable ecosystem

• Authors:
  • Williams, M.
  • Maratha, P.
  • Killi, D.
  • Forristal, D.
  • Lanigan, G.
  • Osborne, B.
  • Prescher, A.
  • Helmy, M.
  • Hastings, A.
  • Abdalla, M.
  • Rueangritsarakul, K.
  • Smith, P.
  • Nolan, P.
  • Jones, M. B.
• Source: Geoderma
• Volume: 223-225
• Year: 2014
• Summary: Field management activities have significant impacts on greenhouse gas (GHG) emissions from cropland soils. In this study, the effectiveness of combining reduced tillage with a mustard cover crop (RT-CC) to mitigate present and future GHG emissions from a fertilized spring barley field in the southeast of Ireland was assessed. The field site which had a free-draining sandy loam soil with low soil moisture holding capacity, had been managed for three years prior to measurements under two different tillage systems; conventional (CT) and RT-CC. Field measurements of soil CO2, N2O and CH4 emissions, crop biomass, water filled pore space (WFPS), soil temperature and soil nitrate were made to capture both steady state conditions as well as the management events. Field data were used to validate the DNDC (DeNitrification-DeComposition) model and future GHG emissions under two sets of climate projections were predicted. Although fertilizer use was the same for both treatments the RT-CC treatment had significantly (p < 0.05) higher N2O emissions for both present and future climate. However, the inclusion of a cover crop with the RT treatment increased predicted soil organic carbon (SOC), which more than compensated for the higher N2O flux resulting in a lower total GHG balance (TGGB) compared with the CT treatment. Results show that the effectiveness of RT-CC in mitigating GHG emissions will depend crucially on the magnitude of compensatory increases in carbon dioxide uptake by the cover crop that will contribute to a reduction in the total GHG balance.

74. Can biochar reduce soil greenhouse gas emissions from a Miscanthus bioenergy crop?

• Authors:
  • Whitaker, J.
  • Reay, D. S.
  • McNamara, N. P.
  • Case, S. D. C.
• Source: GCB Bioenergy
• Volume: 6
• Issue: 1
• Year: 2014
• Summary: Energy production from bioenergy crops may significantly reduce greenhouse gas (GHG) emissions through substitution of fossil fuels. Biochar amendment to soil may further decrease the net climate forcing of bioenergy crop production, however, this has not yet been assessed under field conditions. Significant suppression of soil nitrous oxide (N2O) and carbon dioxide (CO2) emissions following biochar amendment has been demonstrated in short-term laboratory incubations by a number of authors, yet evidence from long-term field trials has been contradictory. This study investigated whether biochar amendment could suppress soil GHG emissions under field and controlled conditions in a MiscanthusxGiganteus crop and whether suppression would be sustained during the first 2years following amendment. In the field, biochar amendment suppressed soil CO2 emissions by 33% and annual net soil CO2 equivalent (eq.) emissions (CO2, N2O and methane, CH4) by 37% over 2years. In the laboratory, under controlled temperature and equalised gravimetric water content, biochar amendment suppressed soil CO2 emissions by 53% and net soil CO2 eq. emissions by 55%. Soil N2O emissions were not significantly suppressed with biochar amendment, although they were generally low. Soil CH4 fluxes were below minimum detectable limits in both experiments. These findings demonstrate that biochar amendment has the potential to suppress net soil CO2 eq. emissions in bioenergy crop systems for up to 2years after addition, primarily through reduced CO2 emissions. Suppression of soil CO2 emissions may be due to a combined effect of reduced enzymatic activity, the increased carbon-use efficiency from the co-location of soil microbes, soil organic matter and nutrients and the precipitation of CO2 onto the biochar surface. We conclude that hardwood biochar has the potential to improve the GHG balance of bioenergy crops through reductions in net soil CO2 eq. emissions.

75. Greenhouse gas intensity of palm oil produced in Colombia addressing alternative land use change and fertilization scenarios

• Authors:
  • Acevedo, H.
  • Castanheira, E. G.
  • Freire, F.
• Source: Applied Energy
• Volume: 114
• Year: 2014
• Summary: The main goal of this article is to assess the life-cycle greenhouse gas (GHG) intensity of palm oil produced in a specific plantation and mill in Colombia. A comprehensive evaluation of the implications of alternative land use change (LUC) scenarios (forest, shrubland, savanna and cropland conversion) and fertilization schemes (four synthetic and one organic nitrogen-fertilizer) was performed. A sensitivity analysis to field nitrous oxide emission calculation, biogas management options at mill, time horizon considered for global warming and multifunctionality approach were also performed. The results showed that the GHG intensity of palm oil greatly depends on the LUC scenario. Significant differences were observed between the LUC scenarios (-3.0 to 5.3 kg CO(2)eq kg(-1) palm oil). The highest result is obtained if tropical rainforest is converted and the lowest if palm is planted on previous cropland, savanna and shrubland, in which almost all LUC from Colombian oil palm area expansion occurred between 1990 and 2009. Concerning plantation and oil extraction, it was shown that field nitrous oxide emissions and biogas management options have a high influence on GHG emissions.

76. Effects of wastewater sludge, urea and charcoal on greenhouse gas emissions in pots planted with wheat

• 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.

77. Sense and nonsense in conservation agriculture: Principles, pragmatism and productivity in Australian mixed farming systems

• 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.

78. Carbon footprints of crops from organic and conventional arable crop rotations - using a life cycle assessment approach

• 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.

79. Modeling cumulative effects in life cycle assessment: The case of fertilizer in wheat production contributing to the global warming potential

• Authors:
  • Kim, J.
  • Guillaume, B.
  • Laratte, B.
  • Birregah, B.
• Source: Science of the Total Environment
• Volume: 481
• Year: 2014
• Summary: This paper aims at presenting a dynamic indicator for life cycle assessment (LCA) measuring cumulative impacts over time of greenhouse gas (GHG) emissions from fertilizers used for wheat cultivation and production. Our approach offers a dynamic indicator of global warming potential (GWP), one of the most used indicator of environmental impacts (e.g. in the Kyoto Protocol). For a case study, the wheat production in France was selected and considered by using data from official sources about fertilizer consumption and production of wheat We propose to assess GWP environmental impact based on LCA method. The system boundary is limited to the fertilizer production for 1 ton of wheat produced (functional unit) from 1910 to 2010. As applied to wheat production in France, traditional LCA shows a maximum GWP impact of 500 kg CO2-eg for 1 ton of wheat production, whereas the GWP impact of wheat production over time with our approach to dynamic LCA and its cumulative effects increases to 18,000 kg CO2-eg for 1 ton of wheat production. In this paper, only one substance and one impact assessment indicator are presented. However, the methodology can be generalized and improved by using different substances and indicators. (C) 2014 Elsevier B.V. All rights reserved.

80. Soil ecosystem services and land use in the rapidly changing Orinoco River Basin of Colombia

• Authors:
  • Sanabria, C.
  • Rodriguez, E.
  • Xiomara Pullido, S.
  • Loaiza, S.
  • del Pilar Hurtado, M.
  • Gutierrez, A.
  • Gomez, Y.
  • Chaparro, P.
  • Botero, C.
  • Bernal, J.
  • Arguello, O.
  • Rodriguez, N.
  • Lavelle, P.
  • Velasquez, E.
  • Fonte, S.
• Source: Agriculture, Ecosystems & Environment
• Volume: 185
• Year: 2014
• Summary: In the Orinoco River Basin of eastern Colombia large scale and rapid conversion of natural savannas into commercial agriculture exists as a critical threat for the ecological integrity of this fragile region. The highly acidic and compacted soils inherent to this region require thorough physical and chemical conditioning in order for intensive cropping systems to be established. Assessing the impact of this dramatic soil perturbation on biodiversity, ecosystem services and other elements of the natural capital is an urgent task for designing sustainable management options in the region. To address this need, we evaluated soil macro invertebrate communities and soil-based ecosystem services (climate regulation, hydrologic functions, soil stability provided by macro aggregation and nutrient provision potential) in four major production systems: improved pastures, annual crops (rice, corn and soy bean), oil palm and rubber plantations, and compared them to the original savanna. Fifteen plots of each system were sampled along a 200 km natural gradient of soil and climatic conditions. In each plot, we assessed climate regulation by measuring green house gas emissions (N2O, CH4 and CO2) and C storage in aboveground plant biomass and soil (0-20 cm). Soil biodiversity (macro invertebrate communities) and three other soil-based ecosystem services, were assessed using sets of 12-20 relevant variables associated with each service and synthesized via multivariate analyses into a single indicator for each ecosystem function, adjusted in a range of 0.1-1.0. Savannas yielded intermediate values for most indicators, while each production system appeared to improve at least one ecosystem service. For example, nutrient provision (chemical fertility) was highest in annual cropping systems (0.78 +/- 0.03) due to relatively high concentrations of Ca, Mg, N, K, and available P and low Al saturation. Hydrological functions and climate regulation (C storage and GHG emissions) were generally improved by perennial crops (oil palm and rubber), while indicators for macro invertebrate biodiversity and activity (0.73 +/- 0.05) and soil macro aggregation (0.76 +/- 0.02) were highest within improved pastures. High variability within each system indicates the potential to make improvements in fields with lowest indicator values, while differences among systems suggest the potential to mitigate negative impacts by combining plots with contrasted functions in a strategically designed landscape mosaic. (C) 2014 Elsevier B.V. All rights reserved.