:The carbon sink capacity of the world’s agricultural and degraded soils is 50 to 66% of the historic carbon loss of 42 to 78 gigatons of carbon. The rate of soil organic carbon sequestration with adoption of recommended technologies depends on soil texture and structure, rainfall, temperature, farming system, and soil management. Strategies to increase the soil carbon pool include soil restoration and woodland regeneration, no-till farming, cover crops, nutrient management, manuring and sludge application, improved grazing, water conservation and harvesting, efficient irrigation, agroforestry practices, and growing energy crops on spare lands. An increase of 1 ton of soil carbon pool of degraded cropland soils may increase crop yield by 20 to 40 kilograms per hectare (kg/ha) for wheat, 10 to 20 kg/ha for maize, and 0.5 to 1 kg/ha for cowpeas. As well as enhancing food security, carbon sequestration has the potential to offset fossilfuel emissions by 0.4 to 1.2 gigatons of carbon per year, or 5 to 15% of the global fossil-fuel emissions.

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Soil carbon sequestration impacts on global climate change and food security.

Climate Change 2007 Synthesis report

Common understanding of the causes of land-use and land-cover change is dominated by simplifications which, in turn, underlie many environment-development policies. This article tracks some of the major myths on driving forces of land-cover change and proposes alternative pathways of change that are better supported by case study evidence. Cases reviewed support the conclusion that neither population nor poverty alone constitute the sole and major underlying causes of land-cover change worldwide. Rather, peoples’ responses to economic opportunities, as mediated by institutional factors, drive land-cover changes. Opportunities and

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The causes of land-use and land-cover change: moving beyond the myths

The relationship between soil structure and the ability of soil to stabilize soil organic matter (SOM) is a key element in soil C dynamics that has either been overlooked or treated in a cursory fashion when developing SOM models. The purpose of this paper is to review current knowledge of SOM dynamics within the framework of a newly proposed soil C saturation concept. Initially, we distinguish SOM that is protected against decomposition by various mechanisms from that which is not protected from decomposition. Methods of quantification and characteristics of three SOM pools defined as protected are discussed. Soil organic matter can be: (1) physically stabilized, or protected from decomposition, through microaggregation, or (2) intimate association with silt and clay particles, and (3) can be biochemically stabilized through the formation of recalcitrant SOM compounds. In addition to behavior of each SOM pool, we discuss implications of changes in land management on processes by which SOM compounds undergo protection and release. The characteristics and responses to changes in land use or land management are described for the light fraction (LF) and particulate organic matter (POM). We defined the LF and POM not occluded within microaggregates (53–250 μm sized aggregates as unprotected. Our conclusions are illustrated in a new conceptual SOM model that differs from most SOM models in that the model state variables are measurable SOM pools. We suggest that physicochemical characteristics inherent to soils define the maximum protective capacity of these pools, which limits increases in SOM (i.e. C sequestration) with increased organic residue inputs.

Stabilization mechanisms of soil organic matter: Implications for C-saturation of soils

The Intergovernmental Panel on Climate Change (IPCC) Technical Paper Climate Change and Water draws together and evaluates the information in IPCC Assessment and Special Reports concerning the impacts of climate change on hydrological processes and regimes, and on freshwater resources – their availability, quality, use and management. It takes into account current and projected regional key vulnerabilities, prospects for adaptation, and the relationships between climate change mitigation and water. Its objectives are:

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Climate change and water.

Wind erosion is a major soil degradation phenomenon on the Canadian prairies but its effects on soil productivity are not well quantified. In the spring of 1990, incremental depths of soil (0, 5, 10, 15 and 20 em) were removed with an excavator, to simulate wind erosion at four sites (three dryland and one irrigated) in southern Alberta. Highly significant non-linear relationships were found between the dep~h of desurfacing and subsequent spring wheat grain yields showing that simulated erosion drastically reduced soil productivity. Treatment effects at the irrigated site followed the same trend as the dryland site illustrating that topsoil loss cannot be compensated by adequate soil moisture. The 0-1 em increment of topsoil was worth more (in terms of magnitude of yield loss when it was removed) on the irrigated site followed by the Black, Dark Brown and Brown dryland ·soils.

The influence of simulated erosion on crop growth and the value of topsoil in soil productivity

Greenhouse gas mitigation in agriculture

The core soil bacterial genera and enzyme activities in incubated soils from century-old wheat rotations

We planted continuous wheat, with and without nitrogen fertilizer, onto a preceding long-term (44 yr) experiment with contrasting cropping systems, and measured soil organic carbon (SOC) after 6 yr. Changes in SOC were driven mostly by cumulative plant C inputs, as influenced by yield response to added nitrogen.

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Soil organic carbon changes as influenced by carbon inputs and previous cropping system

We assessed the extent to which summer fallow in the Dark Brown soil zone is likely to return as a response to net return (NR) risk. An economic model was used to identify, delineate, and quantify ...

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H. Henry Janzen

Papers

The influence of simulated erosion on crop growth and the value of topsoil in soil productivity

Greenhouse gas mitigation in agriculture

The core soil bacterial genera and enzyme activities in incubated soils from century-old wheat rotations

Soil organic carbon changes as influenced by carbon inputs and previous cropping system

Will summer fallow re-emerge in the Dark Brown soil zone of the Canadian Prairie as a response to net return risk?