• Authors:
    • Peter,C.
    • Fiore,A.
    • Nendel,C.
    • Xiloyannis,C.
  • Year: 2014
  • Summary: In this paper, we discuss different methods to calculate greenhouse gas field emissions from fertilization and soil carbon changes to be integrated into Carbon Footprint (CFP) of food and biomass products. At regional level, the simple Tier 1 approach proposed in the IPCC (2006a) AFOLU guidelines is often insufficient to account for emission variability which depends on soil type, climate or crop management. However, the extensive data collection required by Tier 2 and 3 approaches is usually considered too complex and time consuming to be practicable in Life Cycle Assessment. We present four case studies to compare Tier 1 with medium-effort Tier 2 and 3 methodologies. Relevant differences were found: for annual crops, a higher Tier approach seems more appropriate to calculate fertilizer-induced field emissions, while for perennial crops the impact on CFP was negligible. To calculate emissions related to soil carbon change higher Tiers are always more appropriate.
  • Authors:
    • Alvaro-Fuentes,J.
    • Plaza-Bonilla,D.
    • Arrue,J. L.
    • Lampurlanes,J.
    • Cantero-Martinez,C.
  • Source: Plant and Soil
  • Volume: 376
  • Issue: 1-2
  • Year: 2014
  • Summary: The duration of soil organic carbon (SOC) sequestration in agricultural soils varies according to soil management, land-use history and soil and climate conditions. Despite several experiments have reported SOC sequestration with the adoption of no-tillage (NT) in Mediterranean dryland agroecosystems scarce information exists about the duration and magnitude of the sequestration process. For this reason, 20 years ago we established in northeast Spain a NT chronosequence experiment to evaluate SOC sequestration duration under Mediterranean dryland conditions. In July 2010 we sampled five chronosequence phases with different years under NT (i.e., 1, 4, 11, and 20 years) and a continuous conventional tillage (CT) field, in which management prevailed unchanged during decades. Soil samples were taken at four depths: 0-5, 5-10, 10-20 and 20-30 cm. The SOC stocks were calculated from the SOC concentration and soil bulk density. Furthermore, we applied the Century ecosystem model to the different stages of the chronosequence to better understand the factors controlling SOC sequestration with NT adoption. Differences in SOC stocks were only found in the upper 5 cm soil layer in which 4, 11 and 20 years under NT showed greater SOC stocks compared with 1 year under NT and the CT phase. Despite no significant differences were found in the total SOC stock (0-30 cm soil layer) there was a noteworthy difference of 5.7 Mg ha(-1) between the phase with the longest NT duration and the phase under conventional tillage. The maximum annual SOC sequestration occurred after 5 years of NT adoption with almost 50% change in the annual rate of SOC sequestration. NT sequestered SOC over the 20 years following the change in management. However, more than 75% of the total SOC sequestered was gained during the first 11 years after NT adoption. The Century model predicted reasonably well SOC stocks over the NT chronosequence. In Mediterranean agroecosystems, despite the continuous use of NT has limited capacity for SOC sequestration, other environmental and agronomic benefits associated to this technique may justify the maintenance of NT over the long-term.
  • Authors:
    • Zhang, W.
    • Huang, Y.
    • Yu, Y. Q.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 178
  • Year: 2013
  • Summary: The timing, magnitude, and regional distribution of soil organic carbon (SOC) changes are uncertain when factoring in climate change and agricultural management practices. The goal of this study is to analyze the implications of changes in climate and agricultural management for Chinese soil carbon sequestration over the next 40 years. We used the Agro-C model to simulate climate and agricultural management scenarios to investigate the combined impacts of climate change and management on future SOC stocks in China's croplands. The model was run for croplands on mineral soils in China, which make up a total of 130 M ha of cropland. The model used climate data (years 2011-2050) from the FGOALS and PRECIS climate models based on four Intergovernmental Panel on Climate Change (IPCC) emissions scenarios. Three equidistant agricultural management scenarios were used. S0 was a current scenario, and S2 was an optimal scenario. Under the S2 scenario, crop yields increased annually by 1%, the proportion of crop residue retained in the field reached 90% by 2050, and the area of no-tillage increased to 50% of the cultivated area by 2050. The S1 scenario applied half of the increased rates in crop yields, residue retention and no-tillage area values that were used in the S2 scenario. Across all croplands in China, the results suggest that SOC will increase under all combinations of climate and management and that the effect of climate change is much smaller than the effect of changes in agricultural management. Most croplands in China show a significant increase in SOC stocks, while very few zones (mainly in northeastern China) show a decrease. Rice paddy soils under the intensive farming management scenario show higher rates of carbon sequestration than dry-land soils. The maximum carbon sequestration potential of the croplands of China is estimated to be 2.39 Pg C under S2. Annual increases in SOC stocks could offset a maximum of 2.9% of the CO 2 emissions from fossil-fuel combustion in 2009. These results suggest that China's croplands, especially rice paddies, may play an important role in C sequestration and future climate change mitigation.
  • Authors:
    • Tatarko, J.
    • Schlegel, A. J.
    • Holman, J. D.
    • Blanco-Canqui, H.
    • Shaver, T. M.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Replacement of fallow in crop-fallow systems with cover crops (CCs) may improve soil properties. We assessed whether replacing fallow in no-till winter wheat (Triticum aestivum L.)-fallow with winter and spring CCs for 5 yr reduced wind and water erosion, increased soil organic carbon (SOC), and improved soil physical properties on a Ulysses silt loam (fine-silty, mixed, superactive, mesic Aridic Haplustolls) in the semiarid central Great Plains. Winter triticale (×Triticosecale Wittm.), winter lentil (Lens culinaris Medik.), spring lentil, spring pea (Pisum sativum L. ssp.), and spring triticale CCs were compared with wheat-fallow and continuous wheat under no-till management. We also studied the effect of triticale haying on soil properties. Results indicate that spring triticale and spring lentil increased soil aggregate size distribution, while spring lentil reduced the wind erodible fraction by 1.6 times, indicating that CCs reduced the soil's susceptibility to wind erosion. Cover crops also increased wet aggregate stability and reduced runoff loss of sediment, total P, and NO3-N. After 5 yr, winter and spring triticale increased SOC pool by 2.8 Mg ha-1 and spring lentil increased SOC pool by 2.4 Mg ha-1 in the 0- to 7.5-cm depth compared with fallow. Triticale haying compared with no haying for 5 yr did not affect soil properties. Nine months after termination, CCs had, however, no effects on soil properties, suggesting that CC benefits are short lived in this climate. Overall, CCs, grown in each fallow phase in no-till, can reduce soil erosion and improve soil aggregation in this semiarid climate. © Soil Science Society of America.
  • Authors:
    • Bartlett, P.
    • Voroney, P.
    • Warland, J.
    • Chang, K. -H
    • Wagner-Riddle, C.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: The DayCENT model was employed to simulate the effects of conventional tillage (CT) and no-till (NT) practices on the dynamics of soil organic carbon (SOC) over 9 yr in a rotational cropping system in Southern Ontario, Canada. Observations of site properties and eddy covariance measurements were used to assess crop productivity, net ecosystem productivity (NEP), and SOC changes. The validated model captured the dynamics of grain yield and net primary production, which indicated that DayCENT can be used to simulate crop productivity for evaluating the effects of tillage on crop residues and heterotrophic respiration (Rh) dynamics. The simulation suggested that CT enhanced the annual Rh relative to NT by 38.4, 93.7 and 64.2 g C m-2 yr-1 for corn (Zea mays L.), soybean [Glycine max (L.) Merr], and winter wheat (Triticum aestivum L.), respectively. The combined effect of incorporating crop residues and increased cultivation factors enhanced Rh in CT by 35% relative to NT after disk cultivation in the spring. The simulated NEP varied with crop species, tillage practices, and timing/length of the growing season. The seasonal variation of the total SOC pool was greater in CT than NT because of tillage effects on C transfer from the active surface SOC pool to the active soil SOC pool at a rate of 50 to 100 g C m-2 yr-1. The NT method practiced during the study period accounted for a 10.7 g C m-2 yr-1 increase in the slow SOC pool. The validated DayCENT model may be applied for longer-term simulations in similar ecosystems for a variety of climate change experiment. © Soil Science Society of America.
  • Authors:
    • De Oliveira Ferreira, A.
    • Briedis, C.
    • Machado Sá, M. F.
    • Tivet, F.
    • De Moraes, A.
    • Lal, R.
    • Dos Santos, J. B.
    • De Moraes Sá, J. C.
    • Eurich, G.
    • Farias, A.
    • Friedrich, T.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 6
  • Year: 2013
  • Summary: Inventories of C and N footprints on a landscape scale are essential tools for estimating C offsets from agricultural emissions. Therefore, the aims of this study conducted in the subtropical humid ecosystem in southern Brazil were to: (i) conduct a soil-specific inventory of landscape soil C and N stocks with reference to soil order, soil texture, and land use/management type; (ii) estimate accretion rates for soil organic C (SOC) and total N (TN) for areas managed under no-till (NT) practices management with reference to native vegetation (NV) based on this inventory; (iii) generate a map of C stocks for each land use system; and (iv) calculate estimated C offset for the region through the use of NT compared to conventional tillage (CT). Soil samples were collected at 324 points to a 1-m depth from the entire region. Soil texture and duration of NT had a strong influence on C and N stocks. The average soil C stock across all types of soils for depths of 0-40 and 40-100 cm was 57.0 and 43.0%, respectively. The extrapolation of C stored in the 0- to 40-cm depth based on the NT management for 11 and 20 yr for 1.52 million hectare (Mha) was 9.08 ± 0.62 Tg (1 Tg = 1012 g) representing 11.9% of the C stored in all soil orders. The long-term of C sink capacity by conversion of arable land from CT to NT in this region is 33.2 Tg of CO2, with the C offset of 22.5% of all anthropogenic emissions.
  • Authors:
    • Guo, X.
    • Drury, C. F.
    • Yang, X.
    • Fan, R.
    • Zhang, X.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 5
  • Year: 2013
  • Summary: Soil aggregates may protect organic matter from mineralization; however, there is a lack of knowledge about the stability and structural features of soil organic carbon (SOC) in aggregate external layers and the internal layers. The amount and characteristics of SOC in external and internal layers of soil dry-sieved aggregates from three land use systems (woodlot, grassland, and arable land) were studied using an aerobic incubation. Structural features of SOC and hot water-extractable C, prior- and post-incubations, were investigated using Fourier transform mid-infrared spectroscopy. Soil organic C concentrations were 11.1 and 6.8% greater in the internal layers than in external layers of soil aggregates in woodlot and grassland systems, respectively, while there was no difference between the aggregate layers in arable soil. The CO2-C evolved during the aerobic incubation was significantly greater from aggregate external layers than from internal layers under all three land use systems. The content of aliphatic-C was significantly greater in aggregate external layers than in internal layers under all three land use systems, while the content of aromatic-C was greater in aggregate internal layers than in external layers for the woodlot and grassland systems only. The SOC in aggregate internal layers had a longer half-life, a greater slow-C pool and a smaller active-C pool than the SOC in aggregate external layers. The SOC is characterized with higher aromatization and stability in aggregate internal layers than in aggregate external layers. The aggregates are better developed and provide strong protection for SOC in the native woodlot and grassland systems but this protection was not evolved in arable land. © Soil Science Society of America, All rights reserved.
  • Authors:
    • Rosolem, C. A.
    • Li, Y.
    • Garcia, R. A.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 5
  • Year: 2013
  • Summary: Growing cover crops in systems under no tillage affects different pools of soil organic matter, and eventually soil physical attributes are modified. The objective of this study was to evaluate changes in soil organic matter and their relationship with soil physical attributes as affected by plant species grown in rotation with soybean [Glycine max (L.) Merr.] under no-till for 3 yr. Crop rotations included grain sorghum [Sorghum bicolor (L.) Moench], ruzigrass [Urochloa ruziziensis (R. Germ, and CM. Evard) Crins] and sorghum mixed with ruzigrass, all grown in fall/winter, followed by pearl millet [Pennisetum americanum (L.) Leeke], sunn hemp (Crotalaria juncea L.) and sorghum-sudangrass [S. bicolor × S. sudanense (Piper) Stapf] grown during the spring, plus a fallow check plot. Soybean was grown as the summer crop. Millet and sorghum-sudangrass cropped in spring showed higher root and shoot production as spring cropping. In fall/winter, sorghum mixed with ruzigrass yielded higher phytomass compared with sole cropping. Soil physical attributes and organic matter fractioning were positively affected by cropping millet and sorghum-sudangrass whereas intermediate effects were observed after sunn hemp. Maintaining fallow in spring had negative effects on soil organic matter and physical properties. Ruzigrass and sorghum mixed with ruzigrass cropped in fall/winter resulted in better soil quality. Spring cover crops were more efficient in changing soil bulk density, porosity, and aggregates down to 0 to 10 cm; on the other hand, fall/winter cropping showed significant effects on bulk density in the uppermost soil layer. Total C levels in soil were increased after a 3-yr rotation period due to poor initial physical conditions. Fractions of particulate organic C, microbial C, and C in macroaggregates were the most affected by crop rotations, and showed high relation with improved soil physical attributes (porosity, density, and aggregates larger than 2 mm). © Soil Science Society of America, All rights reserved.
  • Authors:
    • Young, F. L.
    • Samuel, M. K.
    • Fortuna, A. M.
    • Gollany, H. T.
    • Pan, W. L.
    • Pecharko, M.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 2
  • Year: 2013
  • Summary: Accurate estimates of soil organic C (SOC) stocks are required to determine changes in SOC resulting from agricultural management practices. Our objectives were to: (i) determine total SOC; (ii) estimate the contribution of light fraction C (LF-C) to total SOC; and (iii) simulate SOC dynamics using CQESTR to examine the effect of climate change for three cropping systems in the Pacific Northwest. The LF-C masked small gains or losses in measured SOC for all cropping systems. Simulated data indicated no significant changes in SOC in the top 30 cm of the sweep-tillage winter wheat (Triticum aestivum L.)-tillage fallow rotation (WW-TF) and no-till (NT) spring wheat-chemical fallow rotation (SW-CF/NT), whereas SOC increased in the NT spring barley (Hordeum vulgare L.)-spring wheat rotation (SB-SW/NT). The apparent increase in measured SOC with continuous NT spring cropping was the result of accumulated undecomposed crop residues that contributed to the labile C pool and was confirmed via LF-C analysis. The contributions of the LF-C to total SOC across cropping systems ranged from 13.4 to 18.4% (fall soil samples) and 14.4 to 18.9% (spring soil samples). Modeling predicted no significant change in SOC stocks for the WW-TF and SW-CF/NT rotations, even with a 30% crop biomass increase based on potential climate change scenarios. Differences between the observed and predicted SOC were due to artifacts associated with protocols used to determine SOC that did not completely remove accrued crop residue and could be explained by LF-C, which provided a first approximation of organic C accretion. Copyright © 2013 by the Soil Science Society of America, Inc.
  • Authors:
    • Arkebauer, T. J.
    • Brassil, C. E.
    • Knops, J. M. H.
    • Kochsiek, A. E.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 1
  • Year: 2013
  • Summary: After harvest, the litter-C pool contributes 20 to 23% of the total C present in maize (Zea mays L.)-based agricultural ecosystems. Therefore, understanding litter-C pool dynamics is important in determining the overall C dynamics of the system and its potential to sequester C. We examined litter-C production and in situ decomposition of maize and soybean [Glycine max (L.) Merr.] litter using four annual litter cohorts (2001-2004) in three no-till management regimes: irrigated continuous maize, irrigated maize-soybean rotation, and rainfed maize-soybean rotation. Litter inputs, i.e., litter-C production, was 20 to 30% higher in irrigated fields than the rainfed field, and maize produced approximately twice as much litter C as soybean. Litter losses, i.e., decomposition, were highly variable, but overall, after 3 yr of decomposition, only 20% litter C remained on average. We fit decomposition models to our data to predict litter-C accretion after 10 yr of management. While management and annual variation were important in fitting the model, tissue type increased model fit most, suggesting a strong role of litter physical structure in decomposition. The predicted 10-yr standing litter pool was 15 and 35% higher in the irrigated maize field than the irrigated or rainfed maize-soybean rotations, respectively. Our data clearly show that the litter-C pool is highly dynamic, with as much as a 60% increase within 1 yr. Thus, short-term C sequestration estimates in agricultural ecosystems largely reflect litter-C pool changes, which are primarily driven by litter inputs and not decomposition differences. © Soil Science Society of America.