Surface albedo and soil carbon sequestration are influenced by agricultural management practices which impact the Earth's radiation budget and climate change. In this study we investigate the impact of reduced summer fallowing and reduced tillage in the Canadian Prairies on climate change by estimating the change in radiative forcing due to albedo and soil carbon sequestration. Seasonal variations of albedo, which are dependent on agricultural management practices and soil colour in three soil zones, were derived from 10-day composite 250-m Moderate Resolution Imaging Spectroradiometer (MODIS) data. Using this information, we found an overall increase of surface albedo due to the conversion from summer fallowing to continuous cropping and from conventional tillage (CT) to either no-tillage (NT) or reduced tillage (RT). The increase was dependent on soil brightness, type of vegetation and snow cover. Using data from the Census of Agriculture and taking into consideration both albedo and soil carbon changes, we estimated that from 1981 to 2016, the total radiative forcing for the cropland area in the Canadian Prairies was -405 mu W m(-2) due to the conversion of CT to either NT or RT and about 70% was due to the change in albedo. During the same period, the total radiative forcing was -410 mu W m(-2) due to a reduction in the area under summer fallow and about 62% was due to the change in albedo. The equivalent atmospheric CO2 drawdown from these two management changes from albedo change was about 7.8 and 8.7 Tg CO2 yr(-1), respectively. These results demonstrate that it is important to consider both the changes of soil carbon and surface albedo in evaluating climate change impacts due to agricultural management practices. (C) 2020 Elsevier B.V. All rights reserved.

World soils and terrestrial ecosystems have been a source of atmospheric abundance of CO2 ever since settled agriculture began about 10-13 millennia ago. The amount of CO2-C emitted into the atmosphere is estimated at 136 +/- 55 Pg from terrestrial ecosystems, of which emission from world soils is estimated at 78 +/- 12 Pg. Conversion of natural to agricultural ecosystems decreases soil organic carbon (SOC) pool by 30-50% over 50-100 years in temperate regions, and 50-75% over 20-50 years in tropical climates. The projected global warming, with estimated increase in mean annual temperature of 4-6 degrees C by 2100, may have a profound impact on the total soil C pool and its dynamics. The SOC pool may increase due to increase in biomass production and accretion into the soil due to the so-called CO2 fertilization effect, which may also enhance production of the root biomass. Increase in weathering of silicates due to increase in temperature, and that of the formation of secondary carbonates due to increase in partial pressure of CO2 in soil air may also increase the total C pool. In contrast, however, SOC pool may decrease because of: (i) increase in rate of respiration and mineralization, (ii) increase in losses by soil erosion, and (iii) decrease in protective effects of stable aggregates which encapsulate organic matter. Furthermore, the relative increase in temperature projected to be more in arctic and boreal regions, will render Cryosols under permafrost from a net sink to a net source of CO2 if and when permafrost thaws. Thus, SOC pool of world soils may decrease with increase in mean global temperature. In contrast, the biotic pool may increase primarily because of the CO2 fertilization effect. The magnitude of CO2 fertilization effect may be constrained by lack of essential nutrients (e.g., N, P) and water. The potential of SOC sequestration in agricultural soils of Europe is 70-190 Tg C yr(-1). This potential is realizable through adoption of recommended land use and management, and restoration of degraded soils and ecosystems including wetlands.