Increase Soil Organic Carbon Levels Research Articles

Chinese Grain for Green Program led to highly increased soil organic carbon levels: A meta-analysis

The Grain for Green Program (GGP), initiated in 1999, is the largest ecological restoration project in central and western China. Here, for the first time, we performed a meta-analysis and found that the GGP largely increased the soil organic carbon (SOC). The SOC was increased by 48.1%, 25.4%, and 25.5% at soil depths of 0–20 cm, 20–40 cm, and 40–60 cm, respectively. Moreover, this carbon accumulation has significantly increased over time since GGP implementation. The carbon accumulation showed a significantly more active response to the GGP in the top 20 cm of soil than in the deeper soil layers. Conversion of cropland to forest could lead to significantly greater SOC accumulation than would the conversion of cropland to grassland. Conversion from cropland to woodland could lead to greater SOC accumulation than would the conversion to either shrubland or orchard. Our results suggest that the GGP implementation caused SOC to accumulate and that there remains a large potential for further accumulation of carbon in the soil, which will help to mitigate climate change in the near future.

Uncertainty in soil carbon accounting due to unrecognized soil erosion

The movement of soil organic carbon (SOC) during erosion and deposition events represents a major perturbation to the terrestrial carbon cycle. Despite the recognized impact soil redistribution can have on the carbon cycle, few major carbon accounting models currently allow for soil mass flux. Here, we modified a commonly used SOC model to include a soil redistribution term and then applied it to scenarios which explore the implications of unrecognized erosion and deposition for SOC accounting. We show that models that assume a static landscape may be calibrated incorrectly as erosion of SOC is hidden within the decay constants. This implicit inclusion of erosion then limits the predictive capacity of these models when applied to sites with different soil redistribution histories. Decay constants were found to be 15-50% slower when an erosion rate of 15tsoilha(-1) yr(-1) was explicitly included in the SOC model calibration. Static models cannot account for SOC change resulting from agricultural management practices focused on reducing erosion rates. Without accounting for soil redistribution, a soil sampling scheme which uses a fixed depth to support model development can create large errors in actual and relative changes in SOC stocks. When modest levels of erosion were ignored, the combined uncertainty in carbon sequestration rates was 0.3-1.0t CO2 ha(-1) yr(-1) . This range is similar to expected sequestration rates for many management options aimed at increasing SOC levels. It is evident from these analyses that explicit recognition of soil redistribution is critical to the success of a carbon monitoring or trading scheme which seeks to credit agricultural activities.

The impact of agricultural land use changes on soil organic carbon dynamics in the Danjiangkou Reservoir area of China

Over recent decades, a large uncultivated area has been converted to woodland and shrubland plantations to protect and restore riparian ecosystems in the Danjiangkou Reservoir area, a water source area of China’s Middle Route of the South-to-North Water Transfer Project. Besides water quality, afforestation may alter soil organic carbon (SOC) dynamics and stock in terrestrial ecosystems, but its effects remain poorly quantified and understood. We investigated soil organic C and nitrogen (N) content, and δ 13C and δ 15N values of organic soil in plant root-spheres and open areas in an afforested, shrubland and adjacent cropped soil. Soil C and N recalcitrance indexes (RIC and RIN) were calculated as the ratio of unhydrolyzable C and N to total C and N. Afforestation significantly increased SOC levels in plant root-spheres with the largest accumulation of C in the afforested soil. Afforestation also increased belowground biomass. The C:N ratios in organic soil changed from low to high in the order the cropped, the shrubland and the afforested soil. The RIC in the afforested and shrubland were higher than that in cropped soil, but the RIN increased from the afforested to shrubland to cropped soil. The δ15N values of the organic soil was enriched from the afforested to shrubland to cropped soil, indicating an increased N loss from the cropped soil compared to afforested or shrubland soil. Changes in the δ13C ratio further revealed that the decay rate of C in the three land use types was the highest in the cropped soil. Afforestation increased the SOC stocks resulted from a combination of large C input from belowground and low C losses because of decreasing soil C decomposition. Shifts in vegetation due to land use change could alter both the quantity and quality of the soil C and thus, have potential effects on ecosystem function and recovery.

Spatially explicit simulations of soil C dynamics in Southern Brazil: Integrating century and GIS with i_Century

Soil organic carbon (SOC) sequestration in agricultural soils requires appropriate cropping systems and conservation practices that increase crop biomass production. No tillage agriculture provides several advantages to establish “carbon friendly” production systems. Conservation agriculture has greatly expanded over the past three decades in the North Central region of Rio Grande de Sul, the southernmost state of Brazil, with about 6 million ha of land under dryland grain crop agriculture. A shift from intensive conventional tillage to mulch tillage and then no tillage has resulted in increased SOC levels across much of the region as verified in field measurements. In this study a modeling system was constructed by coupling the interactive Century (i_Century) software running Century 4.0 and ArcGIS data layers to simulate the long-term SOC trends in the Ibirubá region, which occupies a land area of 83,500 ha. This system was capable of accounting for cropping system and management practices trends from 1900 to the present times, as well as simulating projections out to the year 2050, capturing periods of decreasing or increasing SOC trends. Simulations performed with the modeling system show that SOC stocks in Ibirubá, estimated at 5.05 Tg C before human activity, decreased to 3.71 Tg C (31%) by 1985. An estimated recovery to 3.97 Tg C by 2005 in response to adoption of SOC-enhancing practices such as conservation tillage and no tillage was observed. Simulations to 2050 with maintenance of these cropping systems and soil management showed that total C stocks could reach 4.21 Tg C, which would still be 21% less than originally present in those soils. The integration of Century with GIS was greatly expedited with the use of the i_Century interface and its readily-accessible database format. Data transfer between the modeling and geoprocessing environment was facilitated for quick visualization and further processing. This approach can be applied for carbon monitoring and accounting schemes at several scales, from the field to the national level.

Life cycle assessment of corn grain and corn stover in the United States

The goal of this study is to estimate the county-level environmental performance for continuous corn cultivation of corn grain and corn stover grown under the current tillage practices for various corn-growing locations in the US Corn Belt. The environmental performance of corn grain varies with its farming location because of climate, soil properties, cropping management, etc. Corn stover, all of the above ground parts of the corn plant except the grain, would be used as a feedstock for cellulosic ethanol. Two cropping systems are under investigation: corn produced for grain only without collecting corn stover (referred to as CRN) and corn produced for grain and stover harvest (referred to as CSR). The functional unit in this study is defined as dry biomass, and the reference flow is 1 kg of dry biomass. The system boundary includes processes from cradle to farm gate. The default allocation procedure between corn grain and stover in the CSR system is the system expansion approach. County-level soil organic carbon dynamics, nitrate losses due to leaching, and nitrogen oxide and nitrous oxide emissions are simulated by the DAYCENT model. Life cycle environmental impact categories considered in this study are total fossil energy use, climate change (referred to as greenhouse gas emissions), acidification, and eutrophication. Sensitivities on farming practices and allocation are included. Simulations from the DAYCENT model predict that removing corn stover from soil could decrease nitrogen-related emissions from soil (i.e., N2O, NO x , and NO3 − leaching). DAYCENT also predicts a reduction in the annual accumulation rates of soil organic carbon (SOC) with corn stover removal. Corn stover has a better environmental performance than corn grain according to all life cycle environmental impacts considered. This is due to lower consumption of agrochemicals and fuel used in the field operations and lower nitrogen-related emissions from the soil. The primary source of total fossil energy associated with biomass production is nitrogen fertilizer, accounting for over 30% of the total fossil energy. Nitrogen-related emissions from soil (i.e., N2O, NO x , and NO3 − leaching) are the primary contributors to all other life cycle environmental impacts considered in this study. The environmental performance of corn grain and corn stover varies with the farming location due to crop management, soil properties, and climate conditions. Several general trends were identified from this study. Corn stover has a lower impact than corn grain in terms of total fossil energy, greenhouse gas emissions, acidification, and eutrophication. Harvesting corn stover reduces nitrogen-related emissions from the soil (i.e., N2O, NO x , NO3 −). The accumulation rate of soil organic carbon is reduced when corn stover is removed, and in some cases, the soil organic carbon level decreases. Harvesting only the cob portion of the stover would reduce the negative impact of stover removal on soil organic carbon sequestration rate while still bringing the benefit of lower nitrogen-related emissions from the soil. No-tillage practices offer higher accumulation rates of soil organic carbon, lower fuel consumption, and lower nitrogen emissions from the soil than the current or conventional tillage practices. Planting winter cover crops could be a way to reduce nitrogen losses from soil and to increase soil organic carbon levels. County-level modeling is more accurate in estimating the local environmental burdens associated with biomass production than national- or regional-level modeling. When possible, site-specific experimental information on soil carbon and nitrogen dynamics should be obtained to reflect the system more accurately. The allocation approach between corn grain and stover significantly affects the environmental performance of each. The preferred allocation method is the system expansion approach where incremental fuel usage, additional nutrients in the subsequent growing season, and changes in soil carbon and nitrogen dynamics due to removing corn stover are assigned to only the collected corn stover.

Estimated soil organic carbon change due to agricultural land management modifications in a semiarid cereal-growing region in Central Spain

Maintaining or increasing soil organic carbon (SOC) in agricultural lands is important for soil productivity, restoration and could potentially be a factor in reducing carbon emissions. In order to implement best practices for maintaining productivity and increasing SOC, there is a need for understanding how management changes may alter SOC levels. This applied study presents a methodology to assess and predict SOC levels to better understand effects modification to land management can have in semiarid central Spain. Results show extensification using longer-term pasture rotations (e.g. 5-year) could increase SOC levels and have an impact on soil restoration important in maintaining productivity. SOC increases brought about by new management may also have a role in contribution to national carbon emission reduction plans.

Impact of Using Paper Mill Sludge for Surface‐Mine Reclamation on Runoff Water Quality and Plant Growth

Paper mills generate large amounts of solid waste consisting of fibrous cellulose, clay, and lime. Paper mill sludge (PMS) can improve reclamation of surface-coal mines where low pH and organic-carbon levels in the spoil cover material can inhibit revegetation. When applied at high rates, however, PMS may adversely impact the quality of surface runoff. Therefore, we applied PMS at 0, 224, and 672 dry Mg ha(-)(1) to 22.1 x 4.6-m plots at a recently mined site and monitored runoff for a total of 13 mo. The zero-rate plots served as controls and received standard reclamation consisting of mulching with hay and fertilization at planting. Compared to the control plots, PMS reduced runoff fourfold to sixfold and decreased erosion from 47 Mg ha(-1) to <1 Mg ha(-1). Most of the reduction occurred in the 2.5 mo before the plots were planted. Flow-weighted average dissolved oxygen concentrations in runoff from plots at the 224 and 672 Mg ha(-1) rates, however, were much lower (</=0.4 vs. 8.2 mg L(-1)) and chemical oxygen demand (COD) was much higher for the 672 Mg ha(-1) rate plots than the control plots during the pre-plant period (7229 vs. 880 mg L(-1)). There were few noteworthy differences in water quality among treatments post-planting, but plant dry-matter yields were greater for the PMS plots than for the controls. The 672 Mg ha(-1) rate did not increase COD or nutrient loads compared to the 224 Mg ha(-1) rate and may have more persistent beneficial effects by increasing soil organic carbon levels and pH to a greater extent.

Life cycle assessment of fuel ethanol derived from corn grain via dry milling

Life cycle analysis enables to investigate environmental performance of fuel ethanol used in an E10 fueled compact passenger vehicle. Ethanol is derived from corn grain via dry milling. This type of analysis is an important component for identifying practices that will help to ensure that a renewable fuel, such as ethanol, may be produced in a sustainable manner. Based on data from eight counties in seven Corn Belt states as corn farming sites, we show ethanol derived from corn grain as E10 fuel would reduce nonrenewable energy and greenhouse gas emissions, but would increase acidification, eutrophication and photochemical smog, compared to using gasoline as liquid fuel. The ethanol fuel systems considered in this study offer economic benefits, namely more money returned to society than the investment for producing ethanol. The environmental performance of ethanol fuel system varies significantly with corn farming sites because of different crop management practices, soil properties, and climatic conditions. The dominant factor determining most environmental impacts considered here (i.e., greenhouse gas emissions, acidification, eutrophication, and photochemical smog formation) is soil related nitrogen losses (e.g., N 2O, NO x , and NO 3 −). The sources of soil nitrogen include nitrogen fertilizer, crop residues, and air deposition. Nitrogen fertilizer is probably the primary source. Simulations using an agro-ecosystem model predict that planting winter cover crops would reduce soil nitrogen losses and increase soil organic carbon levels, thereby greatly improving the environmental performance of the ethanol fuel system.

Melhoria da agregação do solo através do sistema plantio direto

The effects of no-tillage with and without crop rotation previously planned, conventional system including ploughing and disc harrowing on soil particles aggregation were evaluated and compared with native forest on an Red distroferric Oxisol with high clay content from western Parana State. Soils were sampled from all treatments, adequately stored and soil aggregation indices determined were: the mean weight diameter (MWD), the geometric mean diameter (GMD) and the aggregate stability index (AS %). Soil organic carbon was also determined for the different treatments. The results showed highest soil organic carbon and also higher AS %, MWD and GMD for native forest area compared to all other treatments. The no-tillage system, cover crops use and crop rotation contributed to increase soil organic carbon levels, and also AS %, MWD and GMD in both localities and in both soil depths (0,0 – 0,10m and 0,10 – 0,20m). The conventional system, where soil are periodically disturbed provoking soil particles dispersion and soil aggregates collapse, promoted decreasing soil organic carbon levels compared to all other treatments, and also presented lower values for AS %, MWD and GMD, as well lowest aggregates > 2,00mm.