• Authors:
    • Albrecht, S. L.
    • Douglas, C. L., Jr.
    • Reardon, C. L.
    • McCool, D. K.
    • Williams, J. D.
    • Rickman, R. W.
  • Source: Journal of Soil and Water Conservation
  • Volume: 68
  • Issue: 5
  • Year: 2013
  • Summary: Roots, cereal crowns, and stems growing beneath the soil surface provide important resistance to soil erosion. Understanding the amount and distribution of this material in the soil profile could provide insight into resistance to soil erosion by water and improve the performance of soil erosion models, such as the revised universal soil loss equation (RUSLE) and the water erosion prediction project (WEPP). Erosion models use built-in or external crop growth models to populate crop yield and live aboveground and associated belowground biomass databases. We examined two data sets from the dryland small grain production region in the Pacific Northwest of the United States to determine root:shoot ratios, the vertical distribution of root and attached belowground biomass, and incorporated residue from previously grown crops. Data were collected in 1993, 1994, 1995, and 2000 from short-term no-till and conventional tillage experiments conducted near Pendleton, Oregon, and Pullman,Washington, and in 1999 and 2000 from long-term experiments representative of farming practices near Pendleton, Oregon. The crops sampled in the short-term data set included soft white winter and spring wheat (Triticum aestivum L.;WW and SW, respectively), spring peas (Pisum sativum L.; SP), and winter canola (Brassica napus L.;WC). Crops sampled in the long-term study included WW SW, and SP. Data were collected at harvest in both data sets and during three phenologic stages in each of the crops in the short-term data set. Soil samples were collected to a depth of 60 cm (23.6 in) in the short-term and 30 cm (11.9 in) in the long-term experiments. In both sets of measurements, we found greater than 70% of root mass is in the top 10 cm (3.9 in) of the soil profile with the exception of SP, which had 70% of root mass in the top 15 cm (5.9 in) of the soil profile.WC produced significantly more biomass near the soil surface than WW SW, or SP Root-to-shoot biomass ratios, in mature wheat ranged from 0.13 to 0.17 in the top 30 cm (11.9 in) of the soil profile, substantially lower than values suggested for use in WEPP (0.25). In the long-term experiments, soil of the conventionally tilled continuous winter wheat (CWW) plots contained significantly greater biomass than soil of conventionally tilled winter wheat/fallow (CR) and no-till winter wheat/fallow (NT) treatments. There was no significant difference between CWW and conventionally tilled winter wheat/spring pea (WP); however, CWW returned more residue to the soil than WP because SP produced less residue and these residues were incorporated with a field cultivator rather than a moldboard plow. More accurate representation of root development, particularly in winter crops, could improve RUSLE and WEPP performance in the Pacific Northwest where winter conditions have proven difficult to model.
  • Authors:
    • Zhao, J.-S.
    • Hu, R.-G.
    • Iqbal, J.
    • Lin, S.
  • Source: Pedosphere
  • Volume: 23
  • Issue: 5
  • Year: 2013
  • Summary: To compare the CH4 oxidation potential among different land uses and seasons, and to observe its response to monsoon precipitation pattern and carbon and nitrogen parameters, a one-year study was conducted for different land uses (vegetable field, tilled and non-tilled orchard, upland crops and pine forest) in central subtropical China. Results showed significant differences in CH4 oxidation potential among different land uses (ranging from -3.08 to 0.36 kg CH4 ha(-1) year(-1)). Upland with corn-peanut-sweet potato rotation showed the highest CH4 emission, while pine forest showed the highest CH4 oxidation potential among all land uses. Non-tilled citrus orchard (-0.72 +/- 0.08 kg CH4 ha(-1) year(-1)) absorbed two times more CH4 than tilled citrus orchard.(-0.38 +/- 0.06 kg CH4 ha(-1) year(-1)). Irrespective of different vegetation, inorganic N fertilizer application significantly influenced CH4 fluxes across the sites (R-2 = 0.86, P = 0.002). Water-filled pore space, soil microbial biomass carbon, and dissolved nitrogen showed significant effects across different land uses (31% to 38% of variability) in one linear regression model. However, their cumulative interaction was significant for pine forest only, which might be attributed to undisturbed microbial communities legitimately responding to other variables, leading to net CH4 oxidation in the soil. These results suggested that i) natural soil condition tended to create win-win situation for CH4 oxidation, and agricultural activities could disrupt the oxidation potentials of the soils; and ii) specific management practices including but not limiting to efficient fertilizer application and utilization, water use efficiency, and less soil disruption might be required to increase the CH4 uptake from the soil.
  • Authors:
    • Katterer, T.
    • Arvidsson, J.
    • Kainiemi, V.
  • Source: Biology and Fertility of Soils
  • Volume: 49
  • Issue: 5
  • Year: 2013
  • Summary: Reduced tillage is proposed as a method of C sequestration in agricultural soils. However, tillage effects on organic matter turnover are often contradictory and data are lacking on how tillage practices affect soil respiration in northern Europe. This field study (1) quantified the short-term effects of different tillage methods and timing on soil respiration and N mineralisation and (2) examined changes in aggregate size distribution due to different tillage operations and how these relate to soil respiration. The study was conducted on Swedish clay soil (Eutric Cambisol) and compared no-tillage with three forms of tillage applied in early or late autumn 2010: mouldboard ploughing to 20-22 cm and chisel ploughing to 12 or 5 cm depth. Soil respiration, soil temperature, gravimetric water content, mineral N and aggregate size distribution were measured. The results showed that respiration was significantly higher (P < 0.001) in no-till than in tilled plots during the 2 weeks following tillage in early September. Later tillage gave a similar trend but treatments did not differ significantly. Soil tillage and temperature explained 56 % of the variation in respiration. In the early tillage treatment, soil respiration decreased with tillage depth. Mineral N status was not affected by tillage treatment or timing. Soil water content did not differ significantly between tillage practices and therefore did not explain differences in respiration. The results indicate that conventional tillage in early autumn may reduce short-term soil respiration compared with chisel ploughing and no-till in clay soils in northern Europe.
  • Authors:
    • Osborne, B.
    • Richards, M.
    • Khalil, M. I.
    • Williams, M.
    • Mueller, C.
  • Source: Atmospheric Environment
  • Volume: 81
  • Issue: December
  • Year: 2013
  • Summary: Model simulations of C and N dynamics, based on country-specific agricultural and environmental conditions, can provide information for compiling national greenhouse gas (GHG) inventories, as well as insights into potential mitigation options. A multi-pool dynamic model, `ECOSSE' (v5 modified), was used to simulate coupled GHGs and soil organic carbon (SOC) stock changes. It was run for an equivalent time frame of 8 years with inputs from conventionally-tilled arable land cropped with spring barley receiving N fertilizer as calcium ammonium nitrate at 135-159 kg N ha(-1) and crop residues (3 t ha-1 yr-1). The simulated daily N2O fluxes were consistent with the measured values, with R-2 of 033 (p < 0.05) and the total error and bias differences were within 95% confidence levels. The measured seasonal N2O losses were 0.39-0.60% of the N applied, with a modelled estimate of 0.23-0.41%. In contrast, the measured annual N2O loss (integrated) was 0.35% and the corresponding simulated value of 0.45% increased to 0.59% when the sum of the daily fluxes was taken into account. This indicates intermittent gas samplings may miss the peak fluxes. On an 8-year average the modelled N2O emission factor (EF) was 0.53 0.03%. The model successfully predicted the daily heterotrophic respiration (RH), with an R-2 of 0.45 (p <0.05) and the total error and bias differences were within the 95% confidence intervals. The simulated and measured total RH (3149 versus 3072 kg C ha(-1) yr(-1)) was within the cropland average values previously reported. The total measured CH4 fluxes indicated that the unfertilized treatments were a small source (-2.29 g C ha(-1) yr(-1)), whilst the fertilized treatments were a sink (+3.64). In contrast, the simulated values suggested a sink (26.61-31.37 g C ha(-1) yr(-1)), demonstrating fertilizer-induced decreases in CH4 oxidation. On average, based on the simulated SOC content a loss of 516 kg C ha(-1) yr(-1) was indicated, which is within the uncertainty range for temperate regions. Results suggest that the model is suitable for estimating the GHG balance of arable fields. However, further refinements and analyses to fully determine and narrow down the uncertainty ranges for GHG estimates are required. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Franzluebbers, A. J.
    • Andrews, S. S.
    • Kome, C. E.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 68
  • Issue: 4
  • Year: 2013
  • Summary: Simple, yet reliable models are needed to quantify soil organic carbon (SOC) changes for the wide diversity of agricultural management conditions in the United States. We compared the outputs of two relatively simple models currently available for farmers and government-financed farm support agencies: the Carbon (C) Management Evaluation Tool for Voluntary Reporting of Greenhouse Gases (COMET-VR) and the Soil Conditioning Index (SCI). Simulations were conducted for 18 locations throughout the United States for five soil textural regimes (loamy sand, sandy loam, silt loam, clay loam, and silty clay loam), three tillage management systems (conventional tillage [CT], minimum tillage [MT], and no tillage [NT]), and two crop rotations (wheat [Triticum aestivum L.]-potato [Solanum tuberosum L.] and wheat-four-year alfalfa [Medicago sativa L.] in western states and corn [Zea mays L.]-soybean [Glycine max L.] and corn-soybean-wheat in eastern states). Both models ranked SOC change as NT > MT > CT, whereby SOC change decreased with increasing soil disturbance with tillage However, models were divergent with regards to soil texture; SOC change was greater in coarse-textured than in fine-textured soils with COMET-VR, but SOC change was lower in coarse-textured than in fine-textured soils with SCI. For crop rotations, SOC change was greater or equal in simpler than in more complex rotation with COMET-VR, but smaller in simpler than in more complex rotations with SCI. Overall, SOC sequestration predicted by COMET-VR was positively related to SCI score, especially when accounting for differences in environmental conditions of a location. Our results suggest that both Models have value and limitations and that measures of SOC sequestration are predictable with these tools under a diversity of typical management conditions in the United States.
  • Authors:
    • Huelsbergen, K.-J.
    • Munch, J. C.
    • Kuestermann, B.
  • Source: European Journal of Agronomy
  • Volume: 49
  • Issue: August
  • Year: 2013
  • Summary: Two factorial long-term field experiments were carried out at the experimental site of Scheyern, located in southern Germany, 40 km north of Munich (48 degrees 30'0' N, 11 degrees 26'60' E). Here three soil tillage systems were investigated: CT (conventional tillage with moldboard plough, 25 cm plowing depth), RT1 (reduced tillage with chisel plow, 18 cm working depth), and RT2 (reduced tillage with chisel plow, 8 cm working depth). At the same time, three fertilization systems were analyzed (high (N3), medium (N2) and low (N1) mineral N input) with a crop rotation of winter wheat (Triticum aestivum L) - potatoes (Solanum tuberosum L.) - winter wheat-corn (Zea mays L). The long-term effects of tillage and fertilization on yields, soil properties, nitrogen and energy efficiency, as well as greenhouse gas emissions (GGE) were investigated for the period of 1994-2005. On average conventional tillage (CT) produced yields of 8.03 (N1), 8.82 (N2) and 8.88 (N3) GE (grain equivalents) ha(-1) yr(-1); reduced tillage (RT1) yields of 7.82 (N1), 8.54 (N2) and 9.10 (N3) GE ha(-1) yr(-1) and RT2 yields of 6.9 (Ni), 7.82 (N2) and 8.6 (N3) GE ha(-1) yr(-1). The benefit of reduced soil tillage over CT. is a lower consumption of diesel fuel (reduced by 35%) and fossil energy (by 10%), C sequestration and N accumulation in soil. We recorded the highest soil organic carbon (SOC) in the RT2 treatments with the lowest tillage intensity (52.5 Mg ha(-1)) and the lowest SOC reserves in the CT plowed treatments (41.1 Mg ha(-1)). During the reported period, SOC reserves in the plowed treatments decreased by about 300 kg C ha-1 yr-1, whereas they increased by 150-500 kg C ha(-1) yr(-1) in the chiseled treatments. Similar results were achieved with the soil organic nitrogen (SON) reserves based on the type of tillage. This amounted to around 4000 kg ha-1 (CT), 4500 kg ha (RT1) and more than 5000 kg N ha-1 (RT2). The RT1 treatments were marked by high nutrient and energy efficiency. The disadvantage of reduced tillage lies in higher pesticide consumption and stronger soil compaction. The influence of reduced tillage was more pronounced in RT2 than in RT1 (higher SOC and SON content, higher soil dry bulk density, lower consumption of diesel fuel, higher pesticide input). The significant decreases in yield in the RT2 treatments reduced the nitrogen and energy efficiency and raised yield-related greenhouse gas emissions (GGE) in comparison to the RT1 treatments. In the case of reduced tillage combined with high N doses (RT1/N3, RT2/N2, RT2/N3), high N2O emissions of 10 to 12 kg ha(-1) yr(-1) were measured using closed chambers. It was found that as input of mineral N increased, GGE for tillage treatments, both area and yield related also increased. In RT1/N1, negative net GGE were recorded due to high C sequestration combined with moderate N2O and CO2 emissions (-220 kg CO2 (eq) ha(-1) yr(-1), -28 kg CO2 eq GE-(1)), whereas CT/N3 produced the highest net GGE (3587 kg CO2 (eq) ha(-1) yr(-1), 404 kg CO2 eq GE(-1)). (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Wander, M. M.
    • Dunn, J. B.
    • Mueller, S.
    • Kwon, H.-Y.
  • Source: Biomass and Bioenergy
  • Volume: 55
  • Issue: August
  • Year: 2013
  • Summary: Current estimates of life cycle greenhouse gas emissions of biofuels produced in the US can be improved by refining soil C emission factors (EF; C emissions per land area per year) for direct land use change associated with different biofuel feedstock scenarios. We developed a modeling framework to estimate these EFs at the state-level by utilizing remote sensing data, national statistics databases, and a surrogate model for CENTURY's soil organic C dynamics submodel (SCSOC). We estimated the forward change in soil C concentration within the 0-30 cm depth and computed the associated EFs for the 2011 to 2040 period for croplands, grasslands or pasture/hay, croplands/conservation reserve, and forests that were suited to produce any of four possible biofuel feedstock systems [corn (Zea Mays L)-corn, corn-corn with stover harvest, switchgrass (Panicum virgatum L), and miscanthus (Miscanthus x giganteus Greef et Deuter)]. Our results predict smaller losses or even modest gains in sequestration for corn based systems, particularly on existing croplands, than previous efforts and support assertions that production of perennial grasses will lead to negative emissions in most situations and that conversion of forest or established grasslands to biofuel production would likely produce net emissions. The proposed framework and use of the SCSOC provide transparency and relative simplicity that permit users to easily modify model inputs to inform biofuel feedstock production targets set forth by policy. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Mosier, A. R.
    • Chen, D.
    • Lam, S. K.
    • Roush, R.
  • Source: Scientific Reports
  • Volume: 3
  • Issue: July
  • Year: 2013
  • Summary: Concerns about increasing concentrations of greenhouse gases in the atmosphere, primarily carbon dioxide (CO2), have raised worldwide interest in the potential of agricultural soils to be carbon (C) sinks. In Australia, studies that have quantified the effects of improved management practices in croplands on soil C have generally been inconclusive and contradictory for different soil depths and durations of the management changes. We therefore quantitatively synthesised the results of Australian studies using meta-analytic techniques to assess the technical and economic feasibility of increasing the soil C stock by improved management practices. Our results indicate that the potential of these improved practices to store C is limited to the surface 0-10 cm of soil and diminishes with time. None of these widely adopted practices is currently financially attractive under Australia's new legislation known as the Carbon Farming Initiative.
  • Authors:
    • Gerik, T. J.
    • Williams, J. R.
    • Blumenthal, J. M.
    • Potter, S. R.
    • Kemanian, A. R.
    • Meki, M. N.
  • Source: Agricultural Systems
  • Volume: 117
  • Year: 2013
  • Summary: There is an increased demand on agricultural systems in the United States and the world to provide food, fiber, and feedstock for the emerging bioenergy industry. The agricultural intensification that this requires could have positive and negative feedbacks in productivity and the environment. In this paper we used the simulation model EPIC to evaluate the impact of alternative tillage and management systems on grain sorghum (Sorghum bicolor L. Moench) production in central and south Texas and to provide long-term insights into the sustainability of the proposed systems as avenues to increase agricultural output. Three tillage systems were tested: conventional (CT), reduced (RT), and no-tillage (NT). These tillage systems were tested on irrigated and rainfed conditions, and in soils with varying levels of structural erosion control practices (no practice, contour tillage, and contours + terraces). Grain yield differed only slightly across the three tillage systems with an average grain yield of 5.7 Mg ha(-1). Over the course of 100-year simulations, NT and RT systems had higher soil organic carbon (SOC) storage (100 and 91 Mg ha(-1), respectively) than CT (85 Mg ha(-1)), with most of the difference originating in the first 25 years of the simulations. As a result, NT and RT systems showed lower net global warming potentials (GWPs) (0.20 and 0.50 Mg C ha(-1) year(-1)) than CT (0.60 Mg C ha(-1) year(-1)). Irrigated systems had 26% higher grain yields than rainfed systems; yet the high energy needed to pump irrigation water (0.10 Mg C ha(-1) year(-1)) resulted in a higher net GWP for irrigated systems (0.50 vs. 0.40 Mg C ha(-1) year(-1)). Contours and contours + terraces had minimal impact on grain yields, SOC storage and GWP. No-till was the single technology with the largest positive impact on GWP and preservation or enhancement of SOC. Overall, the impact of individual tillage cropping systems on GWP seems to be decoupled from the productivity of a given location as determined by weather or soil type. When expressed per unit of output, high yield locations have a much lower GWP than low yield locations and would be therefore prime targets for production intensification. Published by Elsevier Ltd.
  • Authors:
    • La Scala, N.,Jr.
    • Panosso, A. R.
    • Padovan, M. P.
    • Moitinho, M. R.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 37
  • Issue: 6
  • Year: 2013
  • Summary: The soil is one of the main C pools in terrestrial ecosystem, capable of storing significant C amounts. Therefore, understanding the factors that contribute to the loss of CO2 from agricultural soils is critical to determine strategies reducing emissions of this gas and help mitigate the greenhouse effect. The purpose of this study was to investigate the effect of soil tillage and sugarcane trash on CO2 emissions, temperature and soil moisture during sugarcane (re) planting, over a study period of 15 days. The following managements were evaluated: no-tillage with crop residues left on the soil surface (NTR); without tillage and without residue (NTNR) and tillage with no residue (TNR). The average soil CO2 emission (FCO2) was lowest in NTR (2.16 mu mol m(-2) s(-1)), compared to the managements NTNR (2.90 mu mol m(-2) s(-1)) and TNR (3.22 mu mol m(-2) s(-1)), indicating that the higher moisture and lower soil temperature variations observed in NTR were responsible for this decrease. During the study period, the lowest daily average FCO2 was recorded in NTR (1.28 mu mol m(-2) s(-1)), and the highest in TNR (6.08 mu mol m(-2) s(-1)), after rainfall. A loss of soil CO2 was lowest from the management NTR (367 kg ha(-1) of CO2-C) and differing significantly (p<0.05) from the managements NTNR (502 kg ha(-1) of CO2-C) and TNR (535 kg ha(-1) of CO2-C). Soil moisture was the variable that differed most managements and was positively correlated (r = 0.55, p<0.05) with the temporal variations of CO2 emission from NTR and TNR. In addition, the soil temperature differed (p<0.05) only in management NTR (24 degrees C) compared to NTNR (26 degrees C) and TNR (26.5 degrees C), suggesting that under the conditions of this study, sugarcane trash left on the surface induced an average rise in the of soil temperature of 2 degrees C.