• Authors:
    • Cassman, K. G.
    • Sanchez, P. A.
    • Palm, C. A.
    • Gerard, B. G.
    • Jat, M. L.
    • Stirling, C. M.
    • Powlson, D. S.
  • Source: NATURE CLIMATE CHANGE
  • Volume: 4
  • Issue: 8
  • Year: 2014
  • Summary: The Emissions Gap Report 2013 from the United Nations Environment Programme restates the claim that changing to no-till practices in agriculture, as an alternative to conventional tillage, causes an accumulation of organic carbon in soil, thus mitigating climate change through carbon sequestration. But these claims ignore a large body of experimental evidence showing that the quantity of additional organic carbon in soil under no-till is relatively small: in large part apparent increases result from an altered depth distribution. The larger concentration near the surface in no-till is generally beneficial for soil properties that often, though not always, translate into improved crop growth. In many regions where no-till is practised it is common for soil to be cultivated conventionally every few years for a range of agronomic reasons, so any soil carbon benefit is then lost. We argue that no-till is beneficial for soil quality and adaptation of agriculture to climate change, but its role in mitigation is widely overstated.
  • Authors:
    • Caesar-TonThat, T.
    • Stevens, W. B.
    • Sainju, U. M.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 3
  • Year: 2014
  • Summary: Management practices are needed to reduce soil C losses from croplands converted from Conservation Reserve Program (CRP) grassland. We evaluated the effects of irrigation, tillage, cropping system, and N fertilization on surface residue and soil organic C (SOC) at the 0- to 85-cm depth in relation to crop yields in a sandy loam soil from 2005 to 2011 in croplands converted from CRP in western North Dakota. Treatments were two irrigation practices (irrigated vs. nonirrigated) as the main plot and six cropping systems [CRP, conventional till malt barley (Hordeum vulgare L.) with N fertilizer (CTBN), conventional till malt barley without N fertilizer (CTBO), no-till malt barley- pea (Pisum sativum L.) with N fertilizer (NTB-P), no-till malt barley with N fertilizer (NTBN), and no-till malt barley without N fertilizer (NTBO)] as the split plot arranged in a randomized complete block with three replications. Soil surface residue amount and C content were greater in CRP and NTBN than the other cropping systems. At 0 to 5 cm, SOC was greater in irrigated CRP, but at 0 to 85 cm it was greater in nonirrigated NTBN than most other treatments. At 0 to 20 cm, SOC increased by 0.26 to 1.21 Mg C ha-1 yr-1 in NTB-P and CRP but decreased by 0.02 to 0.68 Mg C ha-1 yr-1 in other cropping systems. Surface residue C and SOC at 0 to 10 cm were related to annualized crop grain yield (R2 = 0.45-0.77, P x≤ 0.12, n = 10). Because of positive C sequestration rate and favorable crop yields, NTB-P may be used as a superior management option to reduce soil C losses and sustain yields in croplands converted from CRP in the northern Great Plains.
  • Authors:
    • Dyck, M.
    • Shahidi, B. M. R.
    • Malhi, S. S.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 144
  • Year: 2014
  • Summary: Agricultural soils under long-term zero tillage (no-till) management have been well known to sequester atmospheric carbon (C) in soil organic matter as well as to reduce emissions of major greenhouse gases. This fact aided the development of the present C offset market around the world and is the basis for no tillage or conservation tillage agriculture as a potential low cost means of reducing greenhouse gas (GHG) emissions. The province of Alberta, Canada currently has C offset protocols under which companies that fail to achieve targeted emission reduction can purchase C credits from agricultural farms that have changed tillage management practices. Our study aimed at quantifying the major GHG carbon dioxide (CO2) emissions from two major agricultural soil types in Western Canada (i.e., Black Chernozem and Gray Luvisol) managed under long-term (~30 years) no-till after tillage reversal. We also studied the influences of soil temperature and soil moisture, nitrogen (N) fertilization (i.e., no N vs. 100kgNha-1) and inherent soil fertility on the magnitude of tillage reversal impact on soil CO2 emissions. Our study revealed that the CO2 emissions were higher after tillage reversal irrespective of N fertilizer applications, soil types and soil physical environment. Comparative study between historic soil C sequestration after the adoption of long-term no-till and the GHG emissions in the form of CO2 fluxes after tillage reversal on these study plots showed that the short-term rates of C emissions after tillage reversal were higher than the long-term rates of C sequestration. However, since the time scales for comparing the sequestration and emission rates were so different, these results are expected and reasonable. These results, however, indicate that increased soil C storage resulting from changes in agricultural management practices are reversible and that the potential for C sequestration is dependent on the long-term trends of management practices.
  • Authors:
    • Baffaut, C.
    • Veith, T. L.
    • Moore, M. T.
    • Potter, T. L.
    • Bryant, R. B.
    • Lizotte, R. E.
    • Sadler, E. J.
    • Tomer, M. D.
    • Locke, M. A.
    • Walbridge, M. R.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 5
  • Year: 2014
  • Summary: Ten years ago, the USDA Agricultural Research Service (ARS) began a series of watershed assessment studies as part of the Conservation Effects Assessment Project (CEAP). In this overview, a decade of research progress in 14 watersheds dominated by rain-fed croplands is reviewed to introduce a special section of this journal issue containing papers describing multiwatershed syntheses. The papers evaluate impacts of agricultural practices on soil quality, stream sediment sources, and the role of climate variability in watershed studies and conservation assessments at the watershed scale. The cross-watershed comparisons help enhance our understanding of emerging conservation technologies in terms of their readiness and suitability for wide-scale adoption. Research from ARS CEAP watershed assessments published during the past 10 years suggests encouraging (1) wider adoption of minimum disturbance technologies to reduce runoff risks associated with applying manure, nutrients, and agrichemicals; (2) adoption of winter cover crops; and (3) a renewed emphasis on riparian corridors to control loads of sediment, phosphorus (P), and other contaminants originating from within (and near) stream channels. The management of agricultural watersheds requires that watershed-scale data can be interpreted and applied in management at the farm scale, and that farm-scale information, including financial and management constraints, can be used to clarify watershed management opportunities and challenges. Substantial research needs remain, including social engagement of agricultural communities, use of multiple conservation practices to account for environmental tradeoffs, improved models to simulate the dynamics of nutrient retention and movement in watersheds, and understanding ecosystem responses to changes in water quality. Moreover, a long-term commitment to understand land use trends, water quality dynamics, climate impacts, and the real effectiveness of precision conservation approaches for improving water quality will help secure agriculture's capacity to provide food, water, and other ecosystem services vital to society.
  • Authors:
    • Taboada, M. A.
    • Scianca, C. M.
    • Varela, M. F.
    • Rubio, G.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 143
  • Year: 2014
  • Summary: Cover crops (CC) provide many benefits to soils but their effect on decomposition of previous crop residues and release of nutrients in continuous no-tillage soybean [Glycine max (L.) Merr.] production are little known. Our objective was to quantify CC effects on decomposition and phosphorus (P) release from soybean residue using litterbags. Three CC species (oat, Avena sativa L.; rye, Secale cereal L.; and rye grass, Lolium multiflorum L.) and a no CC control were evaluated. Temperature, moisture content, microbial biomass and microbial activity were measured in the surface 2cm of soil and residues. Cover crops increased soybean residue decomposition slightly both years (8.2 and 6.4%). Phosphorus release from soybean residue did not show any significant differences. Cover crops increased microbial biomass quantity and activity in both soil and residue samples (p<0.001, p=0.049 for soil and residue microbial biomass; p=0.060, p=0.003 for soil and residue microbial activity, respectively). Increased residue decomposition with CC was associated with higher soil and residue microbial biomass and activity, higher near-surface (0-2cm) moisture content (due to shading) and soil organic carbon enrichment by CC. Even though CC increased soybean residue decomposition (233kgha-1), this effect was compensated for by the annual addition of approximately 6500kgha-1 of CC biomass. This study demonstrated another role for CC when calibrating models that simulate the decomposition of residues in no-tillage systems.
  • Authors:
    • Qiao, X.
    • Liang, Z.
    • Rasaily, R. G.
    • Sarker, K. K.
    • He, J.
    • Li, H.
    • Lu, C.
    • Wang, Q.
    • Li, H.
    • Mchugh, A. D. J.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 137
  • Year: 2014
  • Summary: Soil sodicity and salinization are two major issues concerning agricultural production in Northern China and the affected areas are expanding at a rate of 1-1.5. Mha/year. The effects of two treatments, i.e. no-tillage with subsoiling and straw cover (NTSC) and conventional tillage with ploughing and straw removal (CTSR), on soil physical and chemical properties and yields were compared from 1999 to 2011. The results showed that NTSC reduced soil bulk density in the 0-30. cm soil layer, but more importantly the treatment increased total porosity by 20.9%, water stable aggregates and pore size class distribution. The enhance soil structure and improved infiltration in NTSC treatments contributed to reducing soil salinity by 20.3%-73.4% when compared with CTSR. Soil organic matter was significantly greater to 30. cm in NTSC, while total soil nitrogen was lower than CTSR treatments; however, available P was significantly higher in the 0-5. cm soil surface. During the first 3 years, there was no difference in spring maize yield between NTSC and CTSR, but yield significantly increased in NTSC compared with CTSR during the remaining years due to reduced salinity stress and increased soil health. In conclusion, NTSC soil management practices appear to be a more sustainable approach to farming than conventional methods that utilize intensive tillage and crop residue removal.
  • Authors:
    • Williams, M.
    • Maratha, P.
    • Killi, D.
    • Forristal, D.
    • Lanigan, G.
    • Osborne, B.
    • Prescher, A.
    • Helmy, M.
    • Hastings, A.
    • Abdalla, M.
    • Rueangritsarakul, K.
    • Smith, P.
    • Nolan, P.
    • Jones, M. B.
  • Source: Geoderma
  • Volume: 223-225
  • Year: 2014
  • Summary: Field management activities have significant impacts on greenhouse gas (GHG) emissions from cropland soils. In this study, the effectiveness of combining reduced tillage with a mustard cover crop (RT-CC) to mitigate present and future GHG emissions from a fertilized spring barley field in the southeast of Ireland was assessed. The field site which had a free-draining sandy loam soil with low soil moisture holding capacity, had been managed for three years prior to measurements under two different tillage systems; conventional (CT) and RT-CC. Field measurements of soil CO2, N2O and CH4 emissions, crop biomass, water filled pore space (WFPS), soil temperature and soil nitrate were made to capture both steady state conditions as well as the management events. Field data were used to validate the DNDC (DeNitrification-DeComposition) model and future GHG emissions under two sets of climate projections were predicted. Although fertilizer use was the same for both treatments the RT-CC treatment had significantly (p < 0.05) higher N2O emissions for both present and future climate. However, the inclusion of a cover crop with the RT treatment increased predicted soil organic carbon (SOC), which more than compensated for the higher N2O flux resulting in a lower total GHG balance (TGGB) compared with the CT treatment. Results show that the effectiveness of RT-CC in mitigating GHG emissions will depend crucially on the magnitude of compensatory increases in carbon dioxide uptake by the cover crop that will contribute to a reduction in the total GHG balance.
  • Authors:
    • Zgorelec, Z.
    • Bilandzija, D.
    • Kisic, I.
  • Source: Agriculturae Conspectus Scientificus
  • Volume: 79
  • Issue: 1
  • Year: 2014
  • Summary: Soil carbon stocks are highly vulnerable to human activities (such as tillage), which can decrease carbon stocks significantly. These activities break down soil's organic matter and some carbon is converted to carbon dioxide (CO 2). A part of CO 2 (a greenhouse gas that is one of the main contributor to global warming) is lost from the soil by soil respiration (soil CO 2 efflux). The aim of our study is to determine the soil carbon loss by soil CO 2 efflux under different tillage treatments. The experimental site is characterized by continental climate. Field experiment with six different tillage treatments usually used in this area was set up on Stagnic Luvisols in Daruvar, central lowland Croatia in 1994 with investigation aim on determination of soil degradation by water erosion and later, in 2011, expanded to the research on soil CO 2 efflux. Tillage treatments differed in tools that were used, depth and direction of tillage. Tillage treatments were: black fallow (BF), ploughing up/down the slope to 30 cm (PUDS), no-tillage (NT), ploughing across the slope to 30 cm (PAS), very deep ploughing across the slope to 50 cm (VDPAS) and subsoiling (50 cm) plus ploughing (30 cm) across the slope (SSPAS). Field measurements of soil CO 2 concentrations were conducted during one year (n=14) from November 2011 till November 2012, when cover crop was corn ( Zea mays L.). Preliminary soil sampling for determination of soil total carbon content was conducted in April 2011. This paper presents results of soil total carbon content in the soil surface layer (0-30 cm), the variations of CO 2-C efflux during the year, soil carbon loss by CO 2-C efflux and correlation between soil total carbon content and CO 2-C efflux. The range of soil surface total carbon content varied from 19083.7 kg/ha at BF treatment up to 31073.6 kg/ha at SSPAS treatment. The treatment with the lowest average measured CO 2-C efflux was BF. The average CO 2-C efflux at BF treatment was 7.9 kg CO 2-C/ha/day where CO 2-C efflux varied from 2.3 kg CO 2-C/ha/day up to 22.6 kg CO 2-C/ha/day. The treatment with the highest average measured CO 2-C efflux was NT. Range of CO 2-C efflux at NT treatment varied from 7.8 kg CO 2-C/ha/day up to 65.8 kg CO 2-C/ha/day and the average CO 2-C efflux was 24.4 kg CO 2-C/ha/day. Daily soil total carbon loss by soil respiration ranged from 0.04% at BF treatment up to 0.09% at NT treatment. Soil CO 2-C efflux was fully positively correlated with soil total carbon content (r=0.91). After all mentioned, it can be stated that in these agro-ecological conditions, best tillage practice in sustainable plant production in terms of the lowest daily soil total carbon loss (0.06%) by soil respiration is ploughing to 30 cm (PUDS and PAS). Still, it is necessary to conduct the total soil carbon balance in the future research for better understanding of soil carbon gains and losses.
  • Authors:
    • Bonin, C. L.
    • Lal, R.
  • Source: GCB Bioenergy
  • Volume: 6
  • Issue: 1
  • Year: 2014
  • Summary: Biofuel crops may help achieve the goals of energy-efficient renewable ethanol production and greenhouse gas (GHG) mitigation through carbon (C) storage. The objective of this study was to compare the aboveground biomass yields and soil organic C (SOC) stocks under four crops (no-till corn, switchgrass, indiangrass, and willow) 7years since establishment at three sites in Ohio to determine if high-yielding biofuel crops are also capable of high levels of C storage. Corn grain had the highest potential ethanol yields, with an average of more than 4100Lha(-1), and ethanol yields increased if both corn grain and stover were converted to biofuel, while willow had the lowest yields. The SOC concentration in soils under biofuels was generally unaffected by crop type; at one site, soil in the top 10cm under willow contained nearly 13Mg Cha(-1) more SOC (or 29% more) than did soils under switchgrass or corn. Crop type affected SOC content of macroaggregates in the top 10cm of soil, where macroaggregates in soil under corn had lower C, N and C:N ratios than those under perennial grasses or trees. Overall, the results suggest that no-till corn is capable of high ethanol yields and equivalent SOC stocks to 40cm depth. Long-term monitoring and measurement of SOC stocks at depth are required to determine whether this trend remains. In addition, ecological, energy, and GHG assessments should be made to estimate the C footprint of each feedstock.
  • Authors:
    • Balarezo Giarola, N.
    • Tormena, C.
    • Ball, B.
    • da Silva, A.
    • Locks Guimaraes, R.
  • Source: Scientia Agricola
  • Volume: 71
  • Issue: 2
  • Year: 2014
  • Summary: No-tillage in Brazil is an efficient agricultural system that improves crop productivity whilst controlling erosion caused to the soil by degradation. However, there is some concern regarding soil compaction. Our objective was to determine whether the function of soil structure in sustaining crop growth was dependent on row and interrow positions in long-term no-tillage. We took soil samples from a field in a commercial farm under long-term no-tillage since 1979 on a clayey Oxisol in Southern Brazil. We assessed soil physical quality using the revised Peerlkamp technique and measured bulk density, air-filled porosity and air permeability of intact soil cores. Samples were incubated to assess in vitro N2O and CO2 production. The soil physical and structural properties showed consistent differences between interrow and row positions, where the properties measured were more favorable. The revised Peerlkamp technique proved as efficient as quantitative parameters in discriminating treatment differences. Overall, soil physical conditions in the interrow were less favourable than in the row. Pore continuity did not vary as regards position. This may explain why row position did not influence in vitro N2O and CO2 production. Soil physical quality under no-tillage system is enhanced, at least in the short term, by superficial disturbances in the row as a result of the action of the coulters of the no-tillage seeder.