• Authors:
    • Reicosky,Don C.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 5
  • Year: 2015
  • Authors:
    • Schmer,Marty R.
    • Jin,Virginia L.
    • Wienhold,Brian J.
  • Source: Biomass and Bioenergy
  • Volume: 81
  • Year: 2015
  • Summary: Changes in direct soil organic carbon (SOC) can have a major impact on overall greenhouse gas (GHG) emissions from biofuels when using life-cycle assessment (LCA). Estimated changes in SOC, when accounted for in an LCA, are typically derived from near-surface soil depths (30 cm) could have a large positive or negative impact on overall GHG emissions from biofuels that are not always accounted for. Here, we evaluate how sub-surface SOC changes impact biofuel GHG emissions for corn (Zea mays L.) grain, corn stover, and switchgrass (Panicum virgatum L.) using the (Greenhouse Gases, Regulated Emissions, and Energy Use in the Transportation) GREET model. Biofuel GHG emissions showed as much as a 154% difference between using near-surface SOC stocks changes only or when accounting for both near- and sub-surface SOC stock changes. Differences in GHG emissions highlight the importance of accounting for sub-surface SOC changes especially in bioenergy cropping systems with potential for soil C storage to deeper soil depths. Published by Elsevier Ltd.
  • Authors:
    • Blanco-Canqui,H.
    • Shaver,T. M.
    • Lindquist,J. L.
    • Shapiro,C. A.
    • Elmore,R. W.
    • Francis,C. A.
    • Hergert,G. W.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Cover crops (CCs) can provide multiple soil, agricultural production, and environmental benefits. However, a better understanding of such potential ecosystem services is needed. We summarized the current state of knowledge of CC effects on soil C stocks, soil erosion, physical properties, soil water, nutrients, microbial properties, weed control, crop yields, expanded uses, and economics and highlighted research needs. Our review indicates that CCs are multifunctional. Cover crops increase soil organic C stocks (0.1-1 Mg ha -1 yr -1) with the magnitude depending on biomass amount, years in CCs, and initial soil C level. Runoff loss can decrease by up to 80% and sediment loss from 40 to 96% with CCs. Wind erosion potential also decreases with CCs, but studies are few. Cover crops alleviate soil compaction, improve soil structural and hydraulic properties, moderate soil temperature, improve microbial properties, recycle nutrients, and suppress weeds. Cover crops increase or have no effect on crop yields but reduce yields in water-limited regions by reducing available water for the subsequent crops. The few available studies indicate that grazing and haying of CCs do not adversely affect soil and crop production, which suggests that CC biomass removal for livestock or biofuel production can be another benefit from CCs. Overall, CCs provide numerous ecosystem services (i.e., soil, crop-livestock systems, and environment), although the magnitude of benefits is highly site specific. More research data are needed on the (i) multi-functionality of CCs for different climates and management scenarios and (ii) short- and long-term economic return from CCs.
  • Authors:
    • Almagro, M.
    • Albaladejo, J.
    • Garcia-Franco, N.
    • Martínez-Mena, M.
  • Source: Research Article
  • Volume: 153
  • Issue: 153
  • Year: 2015
  • Summary: Semiarid Mediterranean agroecosystems need the implementation of sustainable land management (SLM) practices in order to maintain acceptable levels of soil organic matter (SOM). The application of SLM practices helps to maintain soil structure and physical-chemical protection of soil organic carbon (SOC), hence improving soil carbon sequestration and mitigating CO2 emissions to the atmosphere. In an organic, rain-fed almond (Prunus dulcis Mill., var. Ferragnes) orchard under reduced tillage (RT), as the habitual management practice during the 14 years immediately preceding the experiment, we studied the effect of two agricultural management practices on soil aggregate distribution and SOC stabilization after four years of implementation. The implemented practices were (1) reduced tillage with a mix of Vicia sativa L. and Avena sativa L. as green manure (RTG) and (2) no-tillage (NT). Four aggregate size classes were differentiated by wet sieving (large and small macroaggregates, microaggregates, and the silt plus clay fraction), and the microaggregates occluded within small macroaggregates (SMm) were isolated. In addition, three organic C fractions were separated within the small macroaggregates and microaggregates, using a density fractionation method: free light fraction (free LF-C), intra-aggregate particulate OM (iPOM-C), and organic C associated with the mineral fraction (mineral-C). The results show that the combination of reduced tillage plus green manure (RTG) was the most-efficient SLM practice for SOC sequestration. The total SOC increased by about 14% in the surface layer (0-5cm depth) when compared to RT. Furthermore, green manure counteracted the effect of tillage on soil aggregate rupture. The plant residue inputs from green manure and their incorporation into the soil by reduced tillage promoted the formation of new aggregates and activated the subsequent physical-chemical protection of OC. The latter mechanism occurred mainly in the fine iPOM-C occluded within microaggregates and mineral-C occluded within small macroaggregates fractions, which together contributed to an increase of up to 30% in the OC concentration in the bulk soil. No-tillage favored the OC accumulation in the mineral-C within the small macroaggregates and in the fine iPOM-C occluded within microaggregates in the surface layer, and in the mineral-C occluded within the small macroaggregates and microaggregates at 5-15cm depth, but four years of cessation of tillage were not enough to significantly increase the total OC in the bulk soil. © 2015 Elsevier B.V..
  • Authors:
    • Rochette, P.
    • Morel, C.
    • Lalande, R.
    • Gagnon, B.
    • Angers, D. A.
    • Ziadi, N.
    • Chantigny, M. H.
  • Source: Canadian Journal of Soil Science
  • Volume: 94
  • Issue: 3
  • Year: 2014
  • Summary: Adoption of conservation practices can induce beneficial changes to soil properties and related crop yields in which magnitude varies according to soil and climatic conditions but usually increases with time. A long-term field experiment was initiated in 1992 at L'Acadie in southern Quebec on a clay loam soil to evaluate the effect of tillage [mouldboard plow (MP) vs. conservation (CT)], synthetic N fertilization (0, 80, and 160 kg N ha -1) and synthetic P fertilization (0, 17.5, and 35 kg P ha -1) on soil functioning and grain yields of a corn-soybean rotation. Soil tillage was performed every year while synthetic fertilizers were applied only to the corn. Results obtained 12 to 20 yr after initiation of the study indicated that CT enhanced organic C accumulation, NO 3-N, P and K availability, microbial biomass and activity, and microbial community structure in the upper soil layer, likely due to leaving crop residues at the soil surface. The MP practice resulted in greater organic C content deeper, near the bottom of the plow layer, which promoted soil microbial activity at that depth. However, soil N 2O emissions were not affected by tillage. The N and P fertilization increased the availability of these nutrients, but had no significant effect on the soil microbial biomass, activity, and structure. Linear relationships were established between soil available P and cumulative P budgets obtained under MP or 0 kg P ha -1 under CT. Crop yields varied by year in this study but on average, MP yielded 10% more corn and 13% more soybeans than CT. Corn yield increased linearly with added synthetic N each year, whereas soybean yield was little affected by residual N, and both crops did not respond to fertilizer P. Response to N fertilization did not differ due to tillage or P. Despite higher costs associated with plowing, the profitability of MP was greater than CT on this clay loam soil due to greater yields. Specialized management practices (e.g., delayed planting, better herbicide selection, fall cover crop, in-row tillage) might help to improve CT performance on these cool, humid fine-textured soils.
  • Authors:
    • Basanta, M.
    • Costantini, A.
    • Alvarez, C. R.
    • Alvarez, C.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 142
  • Year: 2014
  • Summary: Soil management affects distribution and the stocks of soil organic carbon and total nitrogen. The aim of this study was to evaluate the effect of different crop sequences and tillage systems on the vertical distribution and stocks of soil carbon and nitrogen. We hypothesized that no-tillage promotes surface organic carbon and total nitrogen accumulation, but does not affect the C and N stocks, when compared with reduced tillage. In addition, the incorporation of maize in the crop sequence increases total organic carbon and total nitrogen stocks. Observations were carried out in 2010 in an experiment located in the semiarid Argentine Pampa, on an Entic Haplustoll. A combination of three tillage systems (no tillage, no tillage with cover crop in winter and reduced tillage) and two crop sequences (soybean-maize and soybean monoculture) were assessed. After 15 years of management treatments, soil samples to a depth of 100. cm at seven intervals, were taken and analyzed for bulk density, organic carbon and total nitrogen. Total organic carbon stock up to a depth of 100. cm showed significant differences between soils under different tillage systems (reduced tillage. <. no tillage = no tillage with cover crop), the last ones having 8% more than the reduced tillage treatment. Soybean-maize had 3% more organic C up to 100. cm depth than the soybean monoculture. Total nitrogen stock was higher under no-till treatments than under reduced tillage, both at 0-50 and 0-100. cm depths. Total organic carbon stratification ratios (0-5. cm/5-10. cm) were around 1.6 under no-till and lower under reduced tillage. The stratification ratio explains less than 40% of soil carbon stock. Tillage system had a greater impact on soil carbon stock than crop sequence. © 2014 Elsevier B.V.
  • Authors:
    • Saxton, A. M.
    • Wight, J. P.
    • Allen, F. L.
    • Ashworth, A. J.
    • Tyler, D. D.
    • Sams, C. E.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 5
  • Year: 2014
  • Summary: Climate change may be mitigated through soil organic C (SOC) storage under no-tillage; however, crop management influences on SOC are not well defined in all systems. Our objective was to compare long-term C fluxes under two no-tillage sites at Research and Education Centers in Milan (RECM) on Oxyaquic Fragiudalfs and at Middle Tennessee (MTREC) on a Typic Paleudalf in a split-block design with four replications. The whole-block was cropping sequences of corn (Zea mays L.), soybeans [Glycine max (L.) Merr.], and cotton (Gossypium hirsutum L.) with split-block bio-cover treatments of winter wheat (Triticum aestivum L.), hairy vetch [Vicia villosa Roth subsp. villosa], poultry litter, and a fallow control. The same sequences were performed at MTREC without cotton. Soil C flux was calculated at surfaces (0-5 cm) and subsurfaces (5-15 cm) during Year 0, 2, 4, and 8. During the first 2 yr, C losses occurred in all treatments and locations (1.40 and 1.20 Mg ha-1at RECM and MTREC, respectively), with stabilization initiating by Year 4. By Year 8, sequences with high frequencies of soybean and greater temporal complexity gained more surface SOC. Poultry litter bio-covers gained more surface SOC compared to wheat, vetch, and fallow bio-covers (P < 0.05). After 8 yr, surface SOC surpassed initial levels (9.20 and 8.79 Mg ha-1), with mean gains of 1.33 and 1.16 Mg C ha-1at RECM and MTREC, respectively. Losses occurred in subsoils at MTREC and RECM, but by Year 8 several treatments had recovered to near baseline levels. Results suggest surface C storage may be enhanced by crop sequence diversity combined with poultry litter bio-covers in no-till systems, whereas subsurface levels may require more time.
  • Authors:
    • Sauer, T. J.
    • Daigh, A. L.
    • Xiao, X.
    • Horton, R.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 4
  • Year: 2014
  • Summary: The interest in bioenergy crops has raised questions as to the potential of management strategies to preserve soil C pools and soil quality. Since soilsurface CO2 effluxes are a major fate of soil C, knowledge of CO2 efflux's spatial and temporal trends among bioenergy crops will facilitate advances in research on improving terrestrial C-cycle models as well as decision support tools for policy and land-Management. Our objective was to evaluate spatial and temporal dynamics of soil-Surface CO2 effluxes in bioenergy-Based corn (Zea mays L.) and reconstructed prairie systems. Systems evaluated included continuous corn (harvested for grain and 50% of the corn stover) with and without a cover crop, mixed prairies (harvested for aboveground biomass) with and without N fertilization, and corn-soybean [Glycine max (L.) Merr.] rotations harvested for grain. Soil-Surface CO2 effluxes, soil temperature, and soil water contents were monitored weekly from July 2008 to September 2011 and hourly during portions of 2010 and 2011. Annual soil-Surface CO2 effluxes were greater in prairies than row crops and are attributed to greater plant root respiration. Soil-Surface CO2 effluxes spatially varied among intra-crop management zones only for continuous corn with stover removal. However, the cover crop reduced CO2 efflux spatial variability 70% of the time as compared to stover removal without a cover crop. Spatial variability of effluxes was not explained by soil physical properties or conditions. Temperature-induced diurnal fluctuations of CO 2 effluxes were not evident during apparent soil-water redistribution. Further research on the mechanisms behind this process is needed followed by incorporation of mechanisms into CO2 efflux models. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA.
  • Authors:
    • Hartman, D. C.
    • Briedis, C.
    • Lal, R.
    • Tivet, F.
    • De Moraes Sá, J. C.
    • dos Santos, J. Z.
    • dos Santos, J. B.
  • Source: Soil & Tillage Research
  • Volume: 136
  • Year: 2014
  • Summary: No-till (NT) cropping systems have been widely promoted in many regions as an important tool to enhance soil quality and improve agronomic productivity. However, knowledge of their long-term effects on soil organic carbon (SOC) stocks and functional SOC fractions linking soil resilience capacity and crop yield is still limited. The aims of this study were to: (i) assess the long-term (16 years) effects of tillage systems (i.e., conventional - CT, minimum - MT, no-till with chisel - NTch, and continuous no-till cropping systems - CNT) on SOC in bulk soil and functional C fractions isolated by chemical (hot water extractable organic C - HWEOC, permanganate oxidizable C - POXC) and physical methods (light organic C - LOC, particulate organic C - POC, mineral-associated organic C - MAOC) of a subtropical Oxisol to 40cm depth; (ii) evaluate the soil resilience restoration effectiveness of tillage systems, and (iii) assess the relationship between the SOC stock enhancement and crop yield. The crop rotation comprised a 3-year cropping sequence involving two crops per year with soybean (Glycine max, L. Merril) and maize (Zea mays L.) in the summer alternating with winter crops. In 2005, the soil under CNT contained 25.8, 20.9, and 5.3Mgha-1 more SOC (P<0.006) than those under CT, MT, and NTch in 0-40cm layer, representing recovery rates of 1.61, 1.31, and 0.33Mg Cha-1yr-1, respectively. The relative C conversion ratio of 0.398 at CNT was more efficient in converting biomass-C input into sequestered soil C than NTch (0.349), MT (0.136), and CT (0.069). The soil under CNT in 0-10cm depth contained ~1.9 times more HWEOC and POXC than those under CT (P<0.05), and concentrations of LOC and POC physical fractions of SOC were significantly higher throughout the year under CNT. Considering CT as the disturbance baseline, the resilience index (RI) increased in the order of MT (0.10)<NTch (0.43)<CNT (0.54). Grain yield was positively affected by increase in SOC stock, and an increase of 1Mg Cha-1 in 0-20cm depth resulted in an increase in yield equal to ~11 and 26kg grainha-1 of soybean (R2=0.97, P=0.03) and wheat (R2=0.96, P=0.03), respectively. The data presented emphasizes the role of labile fractions in the overall SOC accumulation processes in soils managed under CNT and their positive impacts on the soil resilience restoration and on agronomic productivity. © 2013 Elsevier B.V.
  • Authors:
    • Zhang, Q.
    • Hu, C.
    • Ren, T.
    • Du, Z.
  • Source: Soil and Tillage Research
  • Year: 2014
  • Summary: Physical protection by soil aggregates is critical for building soil organic carbon (SOC) stock. The objective of this study was to identify SOC sequestrated in the microaggregate holding within macroaggregte (mM) fraction after shifting tillage systems in the North China Plain. Soil samples from 0-5 cm layer of a 6-yr field experiment (MP - R, moldboard plow without residue; MP + R, moldboard plow with residue; RT, rotary tillage with residue; NT, no-till with residue) were collected and separated into different water-stable aggregates. The macroaggregate (250-2000 μm) was further isolated into intra-aggregate particulate organic matter (iPOM) fractions by density flotation, dispersion and sieving. The results showed that the SOC concentration of fine iPOM (250f, 53-250 μm) was increased by 23% in RT and 39% in NT compared with MP + R, whereas the difference in the coarse iPOM (250c, >250 μm) was not observed. The ratio of 250f-250c (i.e., 250f/250c) followed the order of NT (2.12) ≈ RT (1.94) > MP + R (1.50) ≈ MP - R (1.47), indicating the alternative tillage systems decreased the turnover rates of macroaggregates. Adoption of NT and RT improved the mM formation by 36% and 23% and mM associated C concentration by 38% and 31% as relative to MP + R system. Additionally, the soil C concentration and storage of the iPOM and silt plus clay fractions located within the microaggregate were higher under NT and RT than that of MP + R and MP - R systems. Thus applying NT and RT improved mM formation and soil C sequestered inside this fraction. We concluded that adoption of NT and RT enhanced SOC sequestration in the microaggregates of surface soil of the intensive agroecosystem of North China. © 2014 Elsevier B.V. All rights reserved.