• Authors:
    • WCI
  • Volume: 2010
  • Year: 2010
  • Summary: Welcome to the Western Climate Initiative (WCI). The WCI is a collaboration of independent jurisdictions working together to identify, evaluate, and implement emissions trading policies to tackle climate change at a regional level. This is a comprehensive effort to reduce greenhouse gas pollution, spur investment in clean-energy technologies that create green jobs and reduce dependence on imported oil.
  • Authors:
    • Grace, P.
    • Kiese, R.
    • Butterbach-Bahl, K.
    • Rowlings, D.
    • Rochester, I.
  • Source: Soil Solutions for a Changing World: proceedings of the 19th World Congress of Soil Science
  • Year: 2010
  • Authors:
    • Walker, C.
    • Edis, R.
    • Li, H.
    • Chen, D.
    • Suter, H.
  • Source: Soil Solutions for a Changing World
  • Year: 2010
  • Authors:
    • Dalal, R. C.
    • Wang, W. J.
  • Source: Soil Solutions for a Changing World
  • Year: 2010
  • Summary: This study aimed to assess the feasibility of predicting ranges in N2O emission with a boundary line approach using a few key driving factors. Intact soil cores (9 cm dia. and ~20 cm in depth) were collected from pasture, cereal cropping and sugarcane lands and incubated at various temperature and moisture conditions after addition of different forms of mineral nitrogen (NH4+ and NO3⎯). The pasture and sugarcane soils showed greater N2O production capacity than the cropping soils with similar mineral N and organic C contents or under similar temperature and water filled pore space (WFPS%), and thus different model parameters need to be used. The N2O emission rates were classified into three ranges: low (< 16 g N2O/ha/day), medium (16 –160 g N2O/ha/day) and high (> 160 g N2O/ha/day). The results indicated that N2O emissions were in the low range when soil mineral N content was below 10 mg N/kg for the cropping soils and below 2 mg N/kg for the pasture and sugarcane soils. In soils with mineral N content exceeding the above thresholds, the emission rates were largely regulated by soil temperature and WFPS and the emission ranges could be estimated using linear boundary line models that incorporated both temperature and WFPS. Using these key driving factors (land use, temperature, WFPS and mineral N content), the boundary line models correctly estimated the emission ranges for 85% of the 247 data points for the cropping soils and 59% of the 271 data points for the pasture and sugarcane soils. In view of the fact that N2O emissions from soil are often very variable and difficult to predict and that the soil and environmental conditions applied in this study differed substantially, the above results suggested that, in terms of accuracy and feasibility, the boundary line approach provides a simple and practical alternative to the use of a single emission factor and more complex process-based models.
  • Authors:
    • Renouf, M. A.
    • Wegener, M. K.
    • Pagan, R. J.
  • Source: The International Journal of Life Cycle Assessment
  • Volume: 15
  • Issue: 9
  • Year: 2010
  • Authors:
    • Fernandes, M. F.
    • Chaer, G. M.
  • Source: Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world
  • Year: 2010
  • Summary: Soil biological and biochemical properties have been proposed as sensitive indicators of soil degradation. Nevertheless, their potential to predict the deterioration of major soil functions related to physical stability, and water and nutrient storage and fluxes has not been validated under experimental conditions. The sensitivity of 16 biological and biochemical variables was contrasted with other eight of chemical or physical nature in a gradient of soil degradation induced by cycles of one, two, three, or four tillage events, plus a no-till control. Twenty-four variables were analysed in soil samples (0-20 cm) collected 60 d after the last cycle. Out of these, 22 were significantly affected by soil disturbance. Six biological (microbial biomass-C, -N, and -C to N ratio; qMic; FDA and urease), two physical (water stable aggregates and aggregate mean diameter) and one chemical variable (org-P) were highly sensitive to soil disturbance. Soil bulk density, invertase activity, organic C and CEC were only slightly sensitive to tillage, whereas qCO 2 and xylanase were not significantly affected by tillage frequency. Although some biological and biochemical properties were highly responsive to soil degradation, there was no general trend of superiority of these variables over those of chemical and physical natures regarding the sensitivity to soil degradation.
  • Authors:
    • Piccolo, M. de C.
    • Feigl, B. J.
    • Cerri, C. C.
    • Cerri, C. E. P.
    • Frazao, L. A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 135
  • Issue: 3
  • Year: 2010
  • Summary: The Brazilian Cerrado soils were incorporated into the agricultural production process in the 1970s. The introduction of pastures and/or annual crops utilizing different management systems produced changes in the dynamics of soil organic matter. This study evaluated the microbial attributes of a Typic Quartzipsamment (Arenosols in FAO classification) in native vegetation, pastures, and soybean cultivation under conventional (CT) and no-till (NT) systems. The soil samples (0-5, 5-10 and 10-20 cm layers) were collected in July 2005 and February 2006 from different systems: native Cerrado (CE), CT for 4 years with soybean (CT4 S), CT for 4 years with soybean in rotation with millet (CT4 S/M), an area that has been under pasture for 22 years (PA22), and an area that remained under pasture for 13 years, followed by NT with soybean in rotation with millet for 5 years (NT5). Soil inorganic N (nitrate and ammonium), microbial C and N and basal respiration were determined. The soil metabolic quotient (qCO 2) and the C mic:C org ratios were calculated. The predominant form of inorganic N in the native Cerrado (CE) and in the pasture area (PA22) was ammonium, while the conventional system (CT4 S/M) and no-till system (NT5) areas presented higher nitrogen availability for crops in the form of nitrate. The microbial C and N concentrations increased in the wet season, and the highest values were found in the Cerrado (CE) and in pasture (PA22) areas, where the permanent soil cover and the lack of soil disturbance by agricultural practices allowed more favorable conditions for microbial development. The CT4 S area presented the highest qCO 2 index and the lowest C mic:C total ratio, indicating that the conversion of total carbon into microbial carbon is less efficient in this system. Since sandy soils are more susceptible to degradation, the use of more conservationist management systems promotes more favorable conditions to microbial development and maintenance.
  • Authors:
    • Saggar, S.
    • de Klein, C. A. M.
    • Ledgard, S. F.
    • Luo, J.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 136
  • Issue: 3-4
  • Year: 2010
  • Summary: Nitrous oxide (N2O) emissions from grazed pastures represent a significant source of atmospheric N2O. With an improved understanding and quantification of N sources, transformation processes, and soil and climatic conditions controlling N2O emissions, a number of management options can be identified to reduce N2O emissions from grazed pasture systems. The mitigation options discussed in this paper are: optimum soil management, limiting the amount of N fertiliser or effluent applied when soil is wet; lowering the amount of N excreted in animal urine by using low-N feed supplements as an alternative to fertiliser N-boosted grass; plant and animal selection for increased N use efficiency, using N process inhibitors that inhibit the conversion of urea to ammonium and ammonium to nitrate in soil; use of stand-off/feed pads or housing systems during high risk periods of N loss. The use of single or multiple mitigation options always needs to be evaluated in a whole farm system context and account for total greenhouse gas emissions including methane and carbon dioxide. They should focus on ensuring overall efficiency gains through decreasing N losses per unit of animal production and achieving a tighter N cycle. Whole-system life-cycle-based environmental analysis should also be conducted to assess overall environmental emissions associated the N2O mitigation options. (C) 2009 Elsevier B.V. All rights reserved.
  • Authors:
    • Sun, O. J.
    • Wang, E. L.
    • Luo, Z. K.
  • Source: Geoderma
  • Volume: 155
  • Issue: 3-4
  • Year: 2010
  • Summary: Soil is the largest reservoir of carbon (C) in the terrestrial biosphere and a slight variation in this pool could lead to Substantial changes in the atmospheric CO2 concentration, thus impact significantly on the global climate. Cultivation of natural ecosystems has led to marked decline in soil C storage, such that conservation agricultural practices (CAPs) are widely recommended as options to increase soil C storage, thereby mitigating climate change. In this review, we summarise soil C change as a result of cultivation worldwide and in Australia. We then combine the available data to examine the effects of adopting CAPs on soil C dynamics in Australian agro-ecosystems. Finally, we discuss the future research priorities related to soil C dynamics. The available data show that in Australian agro-ecosystems, cultivation has led to C loss for more than 40 years, with a total C loss of approximately 51% in the surface 0.1 m of soil. Adoption of CAPs generally increased soil C. Introducing perennial plants into rotation had the greatest potential to increase soil C by 18% compared with other CAPs. However, the same CAPS Could result in different outcomes on soil C under different climate and soil combinations. No consistent trend of increase in soil C was found with the duration of CAP applications, implying that questions remain regarding long-term impact of CAPs. Most of the available data in Australia are limited to the surface 0.1 to 0.3 m of soil. Efforts are needed to investigate soil C change in deeper soil layers in Order to understand the impact of crop root growth and various agricultural practices on C distribution in soil profile. Elevated atmospheric CO2 concentration, global warming and rainfall change Could all alter the C balance of agricultural soils. Because of the complexity of soil C response to management and environmental factors, a system modelling approach Supported by sound experimental data would provide the most effective means to analyse the impact of different management practices and future climate change on soil C dynamics. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
  • Authors:
    • Batlle-Bayer, L.
    • Batjes, N. H.
    • Bindraban, P. S.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 137
  • Issue: 1-2
  • Year: 2010
  • Summary: This paper reviews current knowledge on changes in carbon stocks upon land use conversion in the Brazilian Cerrado. First, we briefly characterize the savanna ecosystem and summarize the main published data on C stocks under natural conditions. The effects of increased land use pressure in the Cerrado and current uncertainties of estimations of changes in land cover and land use are reviewed next. Thereafter, we focus on soil organic carbon (SOC) dynamics due to changes in land use, particularly conversion to pastures and soybean-based cropping systems, and effects of management practices such as soil fertilization, crop rotations and tillage practices. Most studies considered here suggest that more intensive agriculture, which include no-till practices and the implementation of best or recommended management practices (RMP), reduces SOC losses after land use conversion from conventional tillage-based, monocropping systems; however, these studies focussed on the first 0.3 m of soil, or less, and seldom considered full carbon accounting. To better estimate possible global warming mitigation with agriculture in the Cerrado more comprehensive studies are needed that analyse fluxes of the biogenic greenhouse gases (GHG; CO 2, N 2O and CH 4) to determine the net global warming potential (GWP). Follow up studies should include the application of an integrated modelling system, comprised of a Geographic Information System (GIS) linked to dynamic modelling tools, to analyse SOC dynamics and make projections for possible changes in net C flows in the Cerrado region upon defined changes in soil use and management.