• Authors:
    • He, W.
    • Liu, S.
    • Gu, R.
    • Yu, J.
    • Yan, C.
    • Teclemariam, S.
    • Liu, E.
    • Liu, Q.
  • Source: Geoderma
  • Volume: 213
  • Year: 2014
  • Summary: The influence of different tillage practices on soil organic carbon levels is more significant under long-term tillage compared to short-term tillage. Despite the great interest in the effect of no-tillage (NT) management practice on carbon sequestration, the long-term effect of NT practice on soil organic carbon and its fractions in northern China remain unclear. We evaluated the long-term effects (after 17 years) of NT and conventional tillage (CT) practices on soil organic carbon and its fractions at different depths ranging from 0 to 60 cm using a cinnamon soil in Shanxi, China. A randomised block design with three replications was used to evaluate both the tillage and its effects on the yield performance of winter wheat (Triticum aestivum L.). After 17 years, the soil organic carbon (SOC) concentration in the NT soil was greater than that of the CT soil, but only in the layer that was located between 0 and 10 cm. There was a significant accumulation of SOC (0-60 cm) in the NT soil (50.2 Mg C ha(-1)) compared to that observed in the CT soil (46.3 Mg C ha(-1)). The particulate organic matter C (POM-C), dissolved organic C (DOC), and microbial biomass C (MBC) levels in the 0-5 cm layer under NT treatment were 155%, 232%, and 63% greater, respectively, compared to the CT treatment. The POM-C, DOC, and MBC in the 5-10 cm layer under NT treatment were 67%, 123%, and 63% greater, respectively, compared to the CT treatment. Below 10 cm, the labile carbon observed in the NT treatment did not differ from that of the CT treatment. Significantly positive correlations were observed between the SOC and the labile organic C fractions. Moreover, the winter wheat (T. aestivum L) yield increased 28.9% in the NT treatment compared to the CT treatment. The data show that NT is an effective and sustainable management practice that improves carbon sequestration and increases soil fertility, resulting in higher winter wheat yields in the rainfed dryland farming areas of northern China. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Thiele-Bruhn, S.
    • Ludwig, M.
    • Vohland, M.
    • Ludwig, B.
  • Source: Geoderma
  • Volume: 223
  • Year: 2014
  • Summary: Spectral variable selection is an important step in spectroscopic data analysis, as it tends to parsimonious data representation and can result in multivariate models with greater predictive ability. In this study, we used VIS-NIR (visible to near-infrared) diffuse reflectance and DRIFT (diffuse reflectance infrared Fourier transform in the mid-infrared range, MIR) spectroscopy to determine a series of chemical and biological soil properties. Multivariate calibrations were performed with partial least squares regression (PLSR) using the full absorbance spectra (VIS-NIR: 400-2500 nm with 5-nm intervals; MIR: 4000-800 cm(-1) with 4-cm(-1) intervals) and with a combination of PLSR and CARS (competitive adaptive reweighted sampling) to integrate only the most informative key variables. The CARS procedure has as yet not been applied in the field of soil spectroscopy. As set heterogeneity is crucial for an optimal calibration, we tested these approaches to a sample set of 60 agricultural samples covering a broad range of different parent materials, soil textures, organic matter contents and soil pH values. Soil samples were taken from the Ap horizon (0-10 cm depth), air-dried and pulverised before the lab spectroscopic measurements were performed. In a cross-validation approach, the CARS-PLSR method was markedly more accurate than full spectrum-PLSR for all investigated soil variables and both spectral regions. With MIR data and CARS-PLSR, excellent results (indicated by a residual prediction deviation (RPD) greater than 3.0) were obtained for organic carbon (OC), nitrogen (N), microbial biomass-C (C-mic) and pH values; for hot water extractable C (C-hwe), RPD was 2.60. The accuracies obtained with VIS-NIR data were considerably lower than those with the MIR spectra; best results were retrieved for pH and C-mic (approximately quantitative as indicated by RPD values between 2.0 and 2.5). The information content of the MIR data was substantially different from the VIS-NIR information, as indicated by 2D correlation analysis. We found an overall blurred 2D correlation pattern between both spectral regions with moderate to low correlation coefficients, which suggested that the heterogeneity of the studied soil sample population had led to a very complex blurring of overtones and combination bands in the NIR region. Statistical CARS selections were physically reasonable. MIR key wavenumbers for the studied C fractions were inter alia identified at the bands at 2920 cm(-1) and 2850 cm(-1) (both aliphatic CH-groups) and the region between 1740 and 1600 cm(-1) (CO-groups) and represent hydrophobic and hydrophilic compounds of soil organic matter. Important VIS-NIR wavelengths for assessing C fractions and N were located nearby the prominent water absorption band at 1915 nm and the hydroxyl band at 2200 nm. The simplicity of the approach, parsimony of the multivariate models, accuracy levels in the cross-validation and physically reasonable selections indicated a successful operation of the CARS procedure. It should be further examined with a larger number of samples using separate calibration and validation sets. (C) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Liu, H.
    • Huang, S.
    • Yang, X.
    • Zhang, W.
    • Wang, J.
    • Xu, M.
    • Wang, X.
  • Source: Plant and Soil
  • Volume: 380
  • Issue: 1-2
  • Year: 2014
  • Summary: Soil inorganic carbon (SIC), primarily calcium carbonate, is a major reservoir of carbon in arid lands. This study was designed to test the hypothesis that carbonate might be enhanced in arid cropland, in association with soil fertility improvement via organic amendments. We obtained two sets (65 each) of archived soil samples collected in the early and late 2000's from three long-term experiment sites under wheat-corn cropping with various fertilization treatments in northern China. Soil organic (SOC), SIC and their Stable C-13 compositions were determined over the range 0-100 cm. All sites showed an overall increase of SIC content in soil profiles over time. Particularly, fertilizations led to large SIC accumulation with a range of 101-202 g C m(-2) y(-1) in the 0-100 cm. Accumulation of pedogenic carbonate under fertilization varied from 60 to 179 g C m(-2) y(-1) in the 0-100 cm. Organic amendments significantly enhanced carbonate accumulation, in particular in the subsoil. More carbon was sequestrated in the form of carbonate than as SOC in the arid cropland in northern China. Increasing SOC stock through long-term straw incorporation and manure application in the arid and semi-arid regions also enhanced carbonate accumulation in soil profiles.
  • Authors:
    • Yu, Q.
    • Song, X. D.
    • Wang, E. L.
    • Luo, Z. K.
    • King, D.
    • Bryan, B. A.
    • Zhao, G.
  • Source: GLOBAL CHANGE BIOLOGY
  • Volume: 19
  • Issue: 5
  • Year: 2013
  • Summary: Quantifying soil organic carbon (SOC) dynamics at a high spatial and temporal resolution in response to different agricultural management practices and environmental conditions can help identify practices that both sequester carbon in the soil and sustain agricultural productivity. Using an agricultural systems model (the Agricultural Production Systems sIMulator), we conducted a high spatial resolution and long-term (122 years) simulation study to identify the key management practices and environmental variables influencing SOC dynamics in a continuous wheat cropping system in Australia's 96 million ha cereal-growing regions. Agricultural practices included five nitrogen application rates (0-200 kg N ha -1 in 50 kg N ha -1 increments), five residue removal rates (0-100% in 25% increments), and five residue incorporation rates (0-100% in 25% increments). We found that the change in SOC during the 122-year simulation was influenced by the management practices of residue removal (linearly negative) and fertilization (nonlinearly positive) - and the environmental variables of initial SOC content (linearly negative) and temperature (nonlinearly negative). The effects of fertilization were strongest at rates up to 50 kg N ha -1, and the effects of temperature were strongest where mean annual temperatures exceeded 19°C. Reducing residue removal and increasing fertilization increased SOC in most areas except Queensland where high rates of SOC decomposition caused by high temperature and soil moisture negated these benefits. Management practices were particularly effective in increasing SOC in south-west Western Australia - an area with low initial SOC. The results can help target agricultural management practices for increasing SOC in the context of local environmental conditions, enabling farmers to contribute to climate change mitigation and sustaining agricultural production.
  • 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:
    • 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:
    • Butterbach-Bahl, K.
    • Murphy, D. V.
    • Barton, L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 167
  • Year: 2013
  • Summary: Semi-arid lands represent one fifth of the global land area but our understanding of greenhouse gas fluxes from these regions is poor. We investigated if inclusion of a grain legume and/or lime in a crop rotation altered greenhouse gas emissions from an acidic soil. Nitrous oxide (N 2O) and methane (CH 4) fluxes were measured from a rain-fed, cropped soil in a semi-arid region of Australia for two years on a sub-daily basis. The randomised-block design included two cropping rotations (lupin-wheat, wheat-wheat) by two liming treatments (0, 3.5 t ha -1) by three replicates. The lupin-wheat rotation only received N fertilizer during the wheat phase (20 kg N ha -1), while the wheat-wheat received 125 kg N ha -1 during the two year study. Fluxes were measured using soil chambers connected to a fully automated system that measured N 2O and CH 4 by gas chromatography. Nitrous oxide fluxes were low (-1.4 to 9.2 g N 2O-N ha -1 day -1), and less than those reported for arable soils in temperate climates. Including a grain legume in the cropping rotation did not enhance soil N 2O; total N 2O losses were approximately 0.1 kg N 2O-N ha -1 after two years for both lupin-wheat and wheat-wheat rotations when averaged across liming treatment. Liming decreased cumulative N 2O emissions from the wheat-wheat rotation by 30% by lowering the contribution of N 2O emissions following summer-autumn rainfall events, but had no effect on N 2O emissions from the lupin-wheat rotation. Daily CH 4 fluxes ranged from -14 to 5 g CH 4-C ha -1 day -1. Methane uptake after two years was lower from the wheat-wheat rotation (601 g CH 4-C ha -1) than from either lupin-wheat rotations (967 g CH 4-C ha -1), however liming the wheat-wheat rotation increased CH 4 uptake (1078 g CH 4-C ha -1) to a value similar to the lupin-wheat rotation. Liming provides a strategy for lowering on-farm greenhouse gas emissions from N fertilised soils in semi-arid environments via decreased N 2O fluxes and increased CH 4 uptake.
  • Authors:
    • Ganeshan, V.
    • Pramanik, P.
    • Das, T. K.
    • Bhattacharyya, R.
    • Saad, A. A.
    • Sharma, A. R.
  • Source: Web Of Knowledge
  • Volume: 96
  • Issue: 2-3
  • Year: 2013
  • Summary: We evaluated impacts of conservation agriculture (zero tillage, bed planting and residue retention) on changes in total soil N (TSN) and aggregate-associated N storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum) and wheat (Triticum aestivum) crops were grown during the first 3 years (2008-2011) and in the last year, maize (Zea mays) and wheat were cultivated. Results indicate that after 4 years the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had 15 % higher TSN concentrations than conventional tillage and bed planting plots (CT-B) (0.63 g kg(-1) soil) in the 0-5 cm soil layer. CT-B plots had lower soil bulk density that ZT plots in that layer. Plots under ZT-B (0.57 Mg ha(-1)) contained 20 % higher TSN stock in the 0-5 cm soil layer than CT-B plots (0.48 Mg ha(-1)). However, tillage had no impact on TSN concentration or stock in the sub-surface (5-15 and 15-30 cm) soil layers. Thus, in the 0-30 cm soil layer, ZT-B plots contained 6 and 5 % higher (P > 0.05) TSN stock compared with CT-B (2.15 Mg N ha(-1)) and CT-F (2.19 Mg N ha(-1)) plots respectively after 4 years. Plots that received cotton/maize + wheat residue (C/M + W RES) contained 16 % higher TSN concentration than plots with residues removed (N RES; 0.62 g kg(-1) soil) in the surface (0-5 cm) layer. Plots with only cotton/maize residue (C/M RES) or only wheat residue (W RES) retention/incorporation had similar TSN concentrations and stocks in the subsurface layer. Plots under ZT-B also had more macroaggregates (0.25-8 mm) and greater mean weight diameter with lower silt + clay sized particles than CT-B plots in that layer. A greater proportion of large macroaggregates (2-8 mm) in the plots under C/M + W RES compared with N RES were observed. In the 5-15 cm soil layer ZT-B and C/M + W RES treated plots had more macroaggregates and greater mean weight diameter than CT-B and N RES treated plots, respectively. Because of the greater amount of large aggregates, plots under ZT-B and C/M + W RES had 49 and 35 % higher large macroaggregate-associated N stocks than CT-B (38 kg TSN ha(-1)) and N RES (40 kg TSN ha(-1)) plots, respectively, in the 0-5 cm soil layer, although aggregates had similar TSN concentrations in all plots. Both tillage and residue retention had greater effects on aggregate-associated N stocks in the 5-15 cm layers. In addition to N content within large macroaggregates, small macroaggregate-associated N contents were also positively affected by ZT-B and C/M + W RES. Tillage and residue retention interaction effects were not significant for all parameters. Thus, the adoption of ZT in permanent beds with crop residue addition is a better management option for improvement of soil N (and thus possibly a reduced dose of fertilizer N can be adopted in the long run), as the management practice has the potential to improve soil aggregation with greater accumulation of TSN within macroaggregates, and this trend would likely have additive effects with advancing years of the same management practices in this region.
  • Authors:
    • Kennedy, A. C.
    • Bary, A. I.
    • Cogger, C. G.
    • Fortuna, A. M.
  • Source: Journal of Environmental Quality
  • Volume: 42
  • Issue: 6
  • Year: 2013
  • Summary: Biosolids have the potential to improve degraded soils in grain-fallow rotations. Our objectives were to determine if repeated biosolids applications in wheat ( Triticum aestivum L.) - fallow could supply adequate but not excessive N for grain production and increase soil C without creating a high risk of P loss. A replicated on-farm experiment was established in 1994 in central Washington, comparing anaerobically digested biosolids with anhydrous NH 3 and a zero-N control. Biosolids were applied at 5, 7, and 9 Mg ha -1 every fourth year through 2010 and incorporated 10 cm deep, while anhydrous NH 3 plots received 56 kg ha -1 N every second year. Grain yield and protein were determined. Soil chemical, biological, and bulk density analyses were made in 2012. Medium and high biosolids rates significantly increased grain yield (3.63 vs. 3.13 Mg ha -1) and protein (103 vs. 85 g kg -1) compared with anhydrous NH 3 averaged across all crops. The medium biosolids rate had significantly lower bulk density (1.05 vs. 1.22 g kg -1) and greater total C (0-10-cm depth) (16.9 vs. 9.4 g kg -1), mineralizable N (156 vs. 52 mg kg -1), and extractable P (114 vs. 16 mg kg -1) than anhydrous NH 3. The P index site vulnerability increased from low for anhydrous NH 3 to medium for the biosolids treatments. Soil NO 3-N was nearly always <10 mg N kg -1 soil (0-30-cm depth). Medium and high biosolids rates significantly increased bacteria/fungi ratios, Gram-negative bacteria, and anaerobic bacteria markers compared with anhydrous NH 3. Biosolids can be an agronomically and environmentally sound management practice in wheat-fallow systems.