• Authors:
    • Mangum, R. W.
    • Coffman, C. B.
    • Teasdale, J. R.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 5
  • Year: 2007
  • Summary: There have been few comparisons of the performance of no-tillage cropping systems vs. organic farming systems, particularly on erodible, droughty soils where reduced-tillage systems are recommended. In particular, there is skepticism whether organic farming can improve soils as well as conventional no-tillage systems because of the requirement for tillage associated with many organic farming operations. A 9-yr comparison of selected minimum-tillage strategies for grain production of corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) was conducted on a sloping, droughty site in Beltsville, MD, from 1994 to 2002. Four systems were compared: (i) a standard mid-Atlantic no-tillage system (NT) with recommended herbicide and N inputs, (ii) a cover crop-based no-tillage system (CC) including hairy vetch (Vicia villosa Roth) before corn, and rye (Secale cereale L.) before soybean, with reduced herbicide and N inputs, (iii) a no-tillage crownvetch (Coronilla varia L.) living mulch system (CV) with recommended herbicide and N inputs, and (iv) a chisel-plow based organic system (OR) with cover crops and manure for nutrients and postplanting cultivation for weed control. After 9 yr, competition with corn by weeds in OR and by the crownvetch living mulch in CV was unacceptable, particularly in dry years. On average, corn yields were 28 and 12% lower in OR and CV, respectively, than in the standard NT, whereas corn yields in CC and NT were similar. Despite the use of tillage, soil combustible C and N concentrations were higher at all depth intervals to 30 cm in OR compared with that in all other systems. A uniformity trial was conducted from 2003 to 2005 with corn grown according to the NT system on all plots. Yield of corn grown on plots with a 9-yr history of OR and CV were 18 and 19% higher, respectively, than those with a history of NT whereas there was no difference between corn yield of plots with a history of NT and CC. Three tests of N availability (corn yield loss in subplots with no N applied in 2003-2005, presidedress soil nitrate test, and corn ear leaf N) all confirmed that there was more N available to corn in OR and CV than in NT. These results suggest that OR can provide greater long-term soil benefits than conventional NT, despite the use of tillage in OR. However, these benefits may not be realized because of difficulty controlling weeds in OR.
  • Authors:
    • Worth, D.
    • Desjardins, R. L.
    • Dyer, J. A.
    • Vergé, X. P. C.
  • Source: Agricultural Systems
  • Volume: 94
  • Issue: 3
  • Year: 2007
  • Summary: In order to demonstrate the impact of an increase in production efficiency on greenhouse gas (GHG) emissions, it is important to estimate the combined methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions per unit of production. In this study, we calculated the GHG emissions from the Canadian dairy industry in 2001 as a fraction of the milk production and per dairy animal. Five regions were defined according to the importance of the dairy industry. N2O and CO2 emissions are directly linked with areas allocated to the dairy crop complex which includes only the crop areas used to feed dairy cattle. The dairy crop complex was scaled down from sector-wide crop areas using the ratios of dairy diet to national crop production of each crop type. Both fertilizer application and on-farm energy consumption were similarly scaled down from sector-wide estimates to the dairy crop complex in each region. The Intergovernmental Panel on Climate Change (IPCC) methodology, adapted for Canadian conditions, was used to calculate CH4 and N2O emissions. Most of the CO2 emission estimates were derived from a Fossil Fuel for Farm Fieldwork Energy and Emissions model except for the energy used to manufacture fertilizers. Methane was estimated to be the main source of GHG, totalling 5.75 Tg CO2 eq with around 80% coming from enteric fermentation and 20% coming from manure management. Nitrous oxide emissions were equal to 3.17 Tg CO2 eq and carbon dioxide emissions were equal to 1.45 Tg. The GHG emissions per animal were 4.55 Mg CO2 eq. On an intensity basis, average GHG emissions were 1.0 kg CO2 eq/kg milk. Methane emissions per kg of milk were estimated at 19.3 l CH4/kg milk which is in agreement with Canadian field measurements.
  • Authors:
    • Adee, E. A.
    • Nafziger ,E. D.
    • Hoeft, R. G.
    • Lal, R.
    • Jagadamma, S.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1-2
  • Year: 2007
  • Summary: Agricultural soils can be a major sink for atmospheric carbon (C) with adoption of recommended management practices (RMPs). Our objectives were to evaluate the effects of nitrogen (N) fertilization and cropping systems on soil organic carbon (SOC) and total N (TN) concentrations and pools. Replicated soil samples were collected in May 2004 to 90 cm depth from a 23-year-old experiment at the Northwestern Illinois Agricultural Research and Demonstration Center, Monmouth, IL. The SOC and TN concentrations and pools, soil bulk density (rho(b)) and soil C:N ratio were measured for five N rates [0 (N-0), 70 (N-1), 140 (N-2), 210 (N-3) and 280 (N-4) kg N ha(-1)] and two cropping systems [continuous corn (Zea mays L.) (CC), and corn-soybean (Glycine max (L.) Merr.) rotation (CS)]. Long-term N fertilization and cropping systems significantly influenced SOC concentrations and pools to 30 cm depth. The SOC pool in 0-30 cm depth ranged from 68.4 Mg ha(-1) for N-0 to 75.8 Mg ha(-1) for N-4. Across all N treatments, the SOC pool in 0-30 cm depth for CC was 4.7 Mg ha(-1) greater than for CS. Similarly, TN concentrations and pools were also significantly affected by N rates. The TN pool for 0-30 cm depth ranged from 5.36 Mg ha(-1) for N-0 to 6.14 Mg ha(-1) for N-4. In relation to cropping systems, the TN pool for 0-20 cm depth for CC was 0.4 Mg ha(-1) greater than for CS. The increase in SOC and TN pools with higher N rates is attributed to the increased amount of biomass production in CC and CS systems. Increasing N rates significantly decreased rho(b) for 0-30 cm and decreased the soil C:N ratio for 0-10 cm soil depth. However, none of the measured soil properties were significantly correlated with N rates and cropping systems below 30 cm, soil depth. We conclude that in the context of developing productive and environmentally sustainable agricultural systems on a site and soil specific basis, the results from this study is helpful to strengthening the database of management effects on SOC storage in the Mollisols of Midwestem U.S. (c) 2007 Elsevier B.V. All rights reserved.
  • Authors:
    • Boast, C. W.
    • Ellsworth, T. R.
    • Mulvaney, R. L.
    • Khan, S. A.
  • Source: Journal of Environmental Quality
  • Volume: 36
  • Issue: 6
  • Year: 2007
  • Summary: Intensive use of N fertilizers in modern agriculture is motivated by the economic value of high grain yields and is generally perceived to sequester soil organic C by increasing the input of crop residues. This perception is at odds with a century of soil organic C data reported herein for Morrow Plots, the world's oldest experimental site under continuous corn (Zea mays L.). After 40 to 50 yr of synthetic fertilization that exceeded grain N removal by 60 to 190%, a net decline occurred in soil C despite increasingly massive residue C incorporation, the decline being more extensive for a corn-soybean (Glycine max L. Merr.) or corn-oats (Avena sativa L.)-hay rotation than for continuous corn and of greater intensity for the profile (0-46 cm) than the surface soil. These findings implicate fertilizer N in promoting the decomposition of crop residues and soil organic matter and are consistent with data from numerous cropping experiments involving synthetic N fertilization in the USA Corn Belt and elsewhere, although not with the interpretation usually provided. These are important implications for soil C sequestration because the yield-based input of fertilizer N has commonly exceeded grain N removal for corn production on fertile soils since the 1960s. To mitigate the ongoing consequences of soil deterioration, atmospheric CO2 enrichment, and NO3- pollution of ground and surface waters, N fertilization should be managed by site-specific assessment of soil N availability. Current fertilizer N managment practices, if combined with corn stover removal for bioenergy production; exacerbate soil C loss.
  • Authors:
    • Field,C. B.
    • Lobell, D. B.
  • Source: Environmental Research Letters
  • Volume: 2
  • Issue: 1
  • Year: 2007
  • Summary: Changes in the global production of major crops are important drivers of food prices, food security and land use decisions. Average global yields for these commodities are determined by the performance of crops in millions of fields distributed across a range of management, soil and climate regimes. Despite the complexity of global food supply, here we show that simple measures of growing season temperatures and precipitation - spatial averages based on the locations of each crop - explain similar to 30% or more of year-to-year variations in global average yields for the world's six most widely grown crops. For wheat, maize and barley, there is a clearly negative response of global yields to increased temperatures. Based on these sensitivities and observed climate trends, we estimate that warming since 1981 has resulted in annual combined losses of these three crops representing roughly 40 Mt or $5 billion per year, as of 2002. While these impacts are small relative to the technological yield gains over the same period, the results demonstrate already occurring negative impacts of climate trends on crop yields at the global scale.
  • Authors:
    • Dolfing, J.
    • Rappoldt, C.
    • Hol, J. M. G.
    • Mosquera, J.
  • Volume: 2010
  • Year: 2007
  • Summary: Soil compaction stimulates the emission of nitrous oxide (N2O) and methane (CH4) from agricultural soils. N2O and CH4 are potent greenhouse gases, with a global warming potential respectively 296 times and 23 times greater than CO2. Agricultural soils are an important source of N2O. Hence there is much interest in a systematic evaluation of management options that are available to minimize agricultural greenhouse gas emissions, in particular N2O soil emissions. One such option would be to minimize soil compaction due to the use of heavy machinery. Soil compaction in arable land is relatively general. Here we report that emissions of N2O and CH4 from an arable field where soil compaction was minimized through application of the so-called "rijpaden" (riding track) system was substantially lower than from plots where a traditional system was used. Laboratory experiments were used to underpin these observations. From these observations we developed a simple calculation model that relates N2O emission to gas filled pore space and soil respiration as input parameters. We suggest to implement the riding track system on clay rather than sand as farmers benefit from lower compaction in terms of lower risk of compaction and better accessibility of fields for work. The potential reduction of the N2O emission from arable farming in the Netherlands is estimated at ~169 ton N2O-N per year (~0.1 Mton CO2-equivalent). This calculation is based on several assumptions and would benefit from testing assumptions and monitoring effects in agricultural day to day practice.
  • Authors:
    • McFee, W. W.
    • Kladivko, E. J.
    • Michéli, E.
    • Vyn, T. J.
    • Gál, A.
  • Source: Soil & Tillage Research
  • Volume: 96
  • Issue: 1-2
  • Year: 2007
  • Summary: Numerous investigators of tillage system impacts on soil organic carbon (OC) or total nitrogen (N) have limited their soil sampling to depths either at or just below the deepest tillage treatment in their experiments. This has resulted in an over-emphasis on OC and N changes in the near-surface zones and limited knowledge of crop and tillage system impacts below the maximum depth of soil disturbance by tillage implements. The objective of this study was to assess impacts of long-term (28 years) tillage and crop rotation on OC and N content and depth distribution together with bulk density and pH on a dark-colored Chalmers silty clay loam in Indiana. Soil samples were taken to 1 m depth in six depth increments from moldboard plow and no-till treatments in continuous corn and soybean-corn rotation. Rotation systems had little impact on the measured soil properties; OC content under continuous corn was not superior to the soybean-corn rotation in either no-till or moldboard plow systems. The increase in OC (on a mass per unit area basis) with no-till relative to moldboard plow averaged 23 t ha(-1) to a constant 30 cm sampling depth, but only 10 t ha(-1) to a constant 1.0 m sampling depth. Similarly, the increase in N with no-till was 1.9 t ha(-1) to a constant 30 cm sampling depth, but only 1.4 t ha(-1) to a constant 1.0 m sampling depth. Tillage treatments also had significant effects on soil bulk density and pH. Distribution of OC and N with soil depth differed dramatically under the different tillage systems. While no-till clearly resulted in more OC and N accumulation in the surface 15 cm than moldboard plow, the relative no-till advantage declined sharply with depth. Indeed, moldboard plowing resulted in substantially more OC and N, relative to no-till, in the 30-50 cm depth interval despite moldboard plowing consistently to less than a 25 cm depth. Our results suggest that conclusions about OC or N gains under long-term no-till are highly dependent on sampling depth and, therefore, tillage comparisons should be based on samples taken well beyond the deepest tillage depth. (c) 2007 Elsevier B.V. All rights reserved.
  • Authors:
    • Hao,X.
    • Kravchenko,A. N.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 1
  • Year: 2007
  • Summary: Management practice and soil texture are known to affect soil C. Relatively little information exists, however, on interactions between textural and management effects. The objective of this study was to evaluate management effects on soil total C along a textural gradient in well-drained Typic Hapludalfs in southwest Michigan. Three management practices considered in this study were conventional tillage (CT) and no-till (NT) both with conventional chemical inputs, and conventional tillage with leguminous cover crops and no chemical inputs (CT-cover). Four replicate plots were sampled for each practice, with approximately 100 soil samples taken at the 0- to 5-cm depth in each plot. In all management practices, the relationships of total C and N with clay + silt varied depending on the range of clay + silt values, with regression slopes at clay + silt 570 g kg-1. Total C in the CT-cover and NT treatments was higher than that in the CT treatment across the whole range of studied textures; however, a greater difference in total C between NT and CT occurred at greater clay + silt contents. Total C in the CT-cover and NT treatments were not different when clay + silt was 600 g kg-1. The results indicate that the potential for C accumulation in surface soils via NT treatment depends on soil texture.
  • Authors:
    • Qi, J.
    • Thelen, K.
    • Kravchenko, A.
    • Senthilkumar, S.
    • Huang, X.
  • Source: Geoderma
  • Volume: 141
  • Issue: 1-2
  • Year: 2007
  • Summary: Accurate mapping of total soil carbon is important for reliable assessment of carbon sequestration potential from a field to regional scales. Highly variable soil and topographical attributes of glacial till terrain cause difficulties in mapping soil carbon based only on a limited number of soil samples. The objectives of this study were to demonstrate the feasibility of mapping total soil carbon using newly developed on-the-go near-infrared spectroscopy (NIRS) measurements and Landsat Enhanced Thematic Mapper (ETM) image reflectance in glacial till soils with and without additional topographical information. The studied field was about 50 ha in size and located in Kalamazoo County of Michigan. The predominant soil is Kalamazoo loam (fine-loamy, mixed, mesic Typic Hapludalfs). NIRS spectra were collected along 22 north-south transects separated by a distance of 25 m and the distance between the measurements within a transect was equal to 5 m. The field was bare of vegetation and relatively dry during soil sampling. Landsat ETM imagery during soil sampling period was obtained. Eighty-five soil samples were collected on the NIRS transects from 0-10 cm depth. Principal component regression was used to relate NIRS spectra and ETM data to measured soil carbon. Regression coefficients between measured and predicted carbon values were equal to 0.70 and 0.46 using NIRS data and ETM imagery, respectively. When topographical attributes, such as elevation and terrain curvature were included into the regression model along with NIRS and ETM data, the regression coefficients improved to 0.81 and 0.62, respectively. The results indicated that combination of the NIRS and ETM measurements with topography is a valuable tool for accurate total carbon mapping in glacial till soils. Field soil moisture and texture were found to be helpful in explaining carbon variation and improving its prediction for ETM imagery data, but were not useful when added to NIRS measurements.
  • Authors:
    • Randall, G. W.
    • Lamb, J. A.
    • Clapp, C. E.
    • Allmaras, R. R.
    • Huggins, D. R.
  • Source: Soil Science Society of America Journal
  • Volume: 71
  • Issue: 1
  • Year: 2007
  • Summary: Soil organic carbon (SOC) in agroecosystems is regulated by crop rotation and soil disturbance. We assessed crop sequence and tillage effects on SOC dynamics and storage using natural 13C abundance of corn (Zea mays L.) and soybean [Glycine max (L.), Merr.]. Treatments consisted of tillage: moldboard plow (MP), chisel plow (CP), and no-tillage (NT); and crop sequence: continuous corn (CC), continuous soybean (SS), and alternating corn-soybean (CS). Soil samples were collected after 14 yr in each treatment and in fallow alley-ways and were analyzed for SOC, {delta}13C, bulk density, and pH. Tillage by crop sequence interactions occurred as treatments with MP and SS as well as fallow averaged 135 Mg SOC ha-1 (0- to 45-cm depth), while CP treatments with corn (CC and CS) and NT with CC averaged 164 Mg SOC ha-1. Crop sequence effects on SOC (0- to 45-cm depth) occurred when tillage was reduced with CP and NT averaging 15% greater SOC in CC than SS. In addition to less C inputs than CC, SS accelerated rates of SOC decomposition. Tillage effects on SOC were greatest in CC where CP had 26% and NT 20% more SOC than MP, whereas SOC in SS was similar across tillage treatments. Up to 33% of the greater SOC under CC for CP and NT, compared with MP, occurred below tillage operating depths. Substantial losses of SOC were estimated (1.6 Mg SOC ha-1 yr-1) despite lowering SOC decay rates with reduced tillage and high levels of C inputs with CC.