• Authors:
    • Hegymegi, P.
    • Gal, A.
    • Smith, D. R.
    • Omonode, R.A.
    • Vyn, T. J.
  • Source: 17th Triennial Conference of the International Soil Tillage Research Organisation (ISTRO)Conference Proceedings
  • Year: 2006
  • Summary: Few researchers have assessed the possibly interacting effects of long-term tillage and rotation practices on organic carbon (OC) sequestration in soil to depths well beyond the maximum depth of tillage operations while also studying carbon dioxide (CO2) emissions from the soil surface of those same experiments. This study was conducted from 2003 to 2005 on tillage and rotation experiments initiated 30 yrs ago in West-Central Indiana on a dark prairie soil with silty clay loam texture.. Our objectives were to determine how tillage systems such as moldboard plow (MP), chisel (CP), and no-till affected OC retention and surface soil CO2 emissions. These tillage systems were investigated in continuous corn and corn-soybean rotations. Soil OC distribution was determined from soil cores in multiple increments to a 1.0 m depth in late 2003 and early 2004. Gas fluxes from the soil surface were measured at weekly or biweekly intervals for up to 14 weeks in the corn growing seasons of 2004 and 2005. The increase in soil OC with no-till relative to moldboard plow averaged just 8 t/ha (or 5% on an equivalent mass basis) in both rotations. Rotation systems had little impact on OC; continuous corn was not superior to the soybean-corn rotation in either no-till or moldboard plow 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, relative to no-till, in the 30-50 cm depth interval despite moldboard plowing consistently to less than a 25 cm depth. Growing season CO2 emissions were significantly affected by rotation but not by tillage treatments. . CO2 emission was higher under continuous corn than with corn following soybean. Our results suggest that conclusions about soil OC gains under long-term no-till are highly dependent on sampling depth and, therefore, tillage comparisons should be based on samples taken much deeper than the deepest depth of direct soil disturbance by tillage implements. After 3 decades of consistent tillage and crop rotation management, tillage system impacts on overall soil OC retention and seasonal CO2 emissions were less than expected. Continuous corn did not store more soil OC than rotation corn, perhaps because continuous corn emitted more CO2 from the soil surface than corn- soybean rotation systems.
  • Authors:
    • Jung, Y. S.
    • Meek, D. W.
    • Cambardella, C. A.
    • Jaynes, D. B.
    • Parkin, T. B.
    • Kaspar, T. C.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 4
  • Year: 2006
  • Summary: Winter cover crops have the potential to increase soil organic C in the corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation in the upper Midwest. Management effects on soil C, however, are often difficult to measure because of the spatial variation of soil C across the landscape. The objective of this study was to determine the effect of oat (Avena sativa L.), rye (Secale cereale L.), and a mixture of oat and rye used as winter cover crops following soybean on soil C levels over 3 yr and both phases of a corn-soybean rotation using terrain attributes as covariates to account for the spatial variability in soil C. A field experiment was initiated in 1996 with cover crop treatments, both phases of a corn-soybean rotation, and a controlled-traffic no-till system. Oat, rye, and oat-rye mixture cover crop treatments were overseeded into the soybean phase of the rotation in late August each year. Cover crop treatments were not planted into or after the corn phase of the rotation. Soil C concentration was measured on 450 samples taken across both rotation phases in a 7.62-m grid pattern in the late spring of 2000, 2001, and 2002. Slope, relative elevation, and wetness index (WI) were used as covariates in the analysis of variance to remove 77% of the variation of soil C caused by landscape driven patterns of soil C. Soil C concentrations were 0.0023 g C g soil -1 higher in 2001 and 0.0016 g C g soil-1 higher in 2002 than in 2000. The main effects of cover crops were not significant, but the interaction of cover crops and rotation phase was significant. The rye cover crop treatment had 0.0010 g C g soil-1 higher soil C concentration than the no-cover- crop control in the soybean phase of the rotation, which included cover crops, but had 0.0016 g C g soil -1 lower C concentrations than the control in the corn phase of the rotation, which did not have cover crops. Using terrain covariates allowed us to remove most of the spatial variability of soil C, but oat and rye cover crops planted every other year after soybean did not increase soil C concentrations averaged over years and rotation phases.
  • Authors:
    • Bullock, D. G.
    • Hao, X.
    • Robertson, G. P.
    • Kravchenko, A. N.
  • Source: Agronomy Journal
  • Volume: 98
  • Issue: 6
  • Year: 2006
  • Summary: Lack of information about the spatial variability of soil C in different management systems limits accurate extrapolation of C sequestration findings to large scales. The objectives of this study were to: (i) describe and quantify variability of total C in three management systems, chisel-plow (CT) and no-till (NT) with conventional chemical inputs and a chisel-plow organic management practice with cover crops (CT-cover) 15 yr after conversion from conventional management; (ii) assess the strengths of spatial correlation in the three studied systems; and (iii) evaluate contributions of topography and texture to the overall total C variability and its spatial components. The data were collected at 12 60 by 60 m plots at the Long Term Ecological Research site, Kellogg Biological Station, MI. The data consisted of elevation measurements taken on a 2 by 5 m grid and a total of 1160 measurements of total C, sand, silt, and clay contents taken from the 0- to 5-cm depth. Overall variability of total C in NT was more than four times greater than in CT, and in CT-cover the variability was more than two times greater than CT. Spatial correlation of total C was the strongest in NT, followed by CT-cover, and then by CT. Stronger spatial structures in NT and CT-cover were found to form in response to topographical and texture gradients. Effects of texture were largely associated with topographical effects; however, even when topography was controlled for, texture still substantially contributed to explaining total C variability.
  • Authors:
    • Rolston, D. E.
    • van Kessel, C.
    • King, A. P.
    • Six, J.
    • Lee, J.
  • Source: Journal of Environmental Quality
  • Volume: 35
  • Issue: 3
  • Year: 2006
  • Summary: There is a lack of understanding of how associations among soil properties and management-induced changes control the variability of greenhouse gas (GHG) emissions from soil. We performed a laboratory investigation to quantify relationships between GHG emissions and soil indicators in an irrigated agricultural field under standard tillage (ST) and a field recently converted (2 yr) to no-tillage (NT). Soil cores (15-cm depth) were incubated at 25{degrees}C at field moisture content and 75% water holding capacity. Principal component analysis (PCA) identified that most of the variation of the measured soil properties was related to differences in soil C and N and soil water conditions under ST, but soil texture and bulk density under NT. This trend became more apparent after irrigation. However, principal component regression (PCR) suggested that soil physical properties or total C and N were less important in controlling GHG emissions across tillage systems. The CO2 flux was more strongly determined by microbial biomass under ST and inorganic N content under NT than soil physical properties. Similarly, N2O and CH4 fluxes were predominantly controlled by NO3- content and labile C and N availability in both ST and NT soils at field moisture content, and NH4+ content after irrigation. Our study indicates that the field-scale variability of GHG emissions is controlled primarily by biochemical parameters rather than physical parameters. Differences in the availability and type of C and N sources for microbial activity as affected by tillage and irrigation develop different levels and combinations of field-scale controls on GHG emissions.
  • Authors:
    • Zhang, F. S.
    • Halvorson, A. D.
    • Mosier, A. R.
    • Liu, X. J.
  • Source: Plant and Soil
  • Volume: 280
  • Issue: 1-2
  • Year: 2006
  • Summary: To evaluate the impact of N placement depth and no-till (NT) practice on the emissions of NO, N2O, CH4 and CO2 from soils, we conducted two N placement experiments in a long-term tillage experiment site in northeastern Colorado in 2004. Trace gas flux measurements were made 2-3 times per week, in zero-N fertilizer plots that were cropped continuously to corn (Zea mays L.) under conventional-till (CT) and NT. Three N placement depths, replicated four times (5, 10 and 15 cm in Exp. 1 and 0, 5 and 10 cm in Exp. 2, respectively) were used. Liquid urea-ammonium nitrate (UAN, 224 kg N ha)1) was injected to the desired depth in the CT- or NT-soils in each experiment. Mean flux rates of NO, N2O, CH4 and CO2 ranged from 3.9 to 5.2 lg N m)2 h)1, 60.5 to 92.4 lg N m)2 h)1, )0.8 to 0.5 lg C m)2 h)1, and 42.1 to 81.7 mg C m)2 h)1 in both experiments, respectively. Deep N placement (10 and 15 cm) resulted in lower NO and N2O emissions compared with shallow N placement (0 and 5 cm) while CH4 and CO2 emissions were not affected by N placement in either experiment. Compared with N placement at 5 cm, for instance, averaged N2O emissions from N placement at 10 cm were reduced by more than 50% in both experiments. Generally, NT decreased NO emission and CH4 oxidation but increased N2O emissions compared with CT irrespective of N placement depths. Total net global warming potential (GWP) for N2O, CH4 and CO2 was reduced by deep N placement only in Exp. 1 but was increased by NT in both experiments. The study results suggest that deep N placement (e.g., 10 cm) will be an effective option for reducing N oxide emissions and GWP from both fertilized CT- and NT-soils.
  • Authors:
    • Liu, X. J.
    • Reule, C. A.
    • Halvorson, A. D.
    • Mosier, A. R.
  • Source: Journal of Environmental Quality
  • Volume: 35
  • Issue: 4
  • Year: 2006
  • Summary: The impact of management on global warming potential (GWP), crop production, and greenhouse gas intensity (GHGI) in irrigated agriculture is not well documented. A no-till (NT) cropping systems study initiated in 1999 to evaluate soil organic carbon (SOC) sequestration potential in irrigated agriculture was used in this study to make trace gas flux measurements for 3 yr to facilitate a complete greenhouse gas accounting of GWP and GHGI. Fluxes of CO2, CH4, and N2O were measured using static, vented chambers, one to three times per week, year round, from April 2002 through October 2004 within conventional-till continuous corn (CT-CC) and NT continuous corn (NT-CC) plots and in NT corn-soybean rotation (NT-CB) plots. Nitrogen fertilizer rates ranged from 0 to 224 kg N ha-1. Methane fluxes were small and did not differ between tillage systems. Nitrous oxide fluxes increased linearly with increasing N fertilizer rate each year, but emission rates varied with years. Carbon dioxide efflux was higher in CT compared to NT in 2002 but was not different by tillage in 2003 or 2004. Based on soil respiration and residue C inputs, NT soils were net sinks of GWP when adequate fertilizer was added to maintain crop production. The CT soils were smaller net sinks for GWP than NT soils. The determinant for the net GWP relationship was a balance between soil respiration and N2O emissions. Based on soil C sequestration, only NT soils were net sinks for GWP. Both estimates of GWP and GHGI indicate that when appropriate crop production levels are achieved, net CO2 emissions are reduced. The results suggest that economic viability and environmental conservation can be achieved by minimizing tillage and utilizing appropriate levels of fertilizer.
  • Authors:
    • Baker, J. M.
    • Molina, J. A. E.
    • Allmaras, R. R.
    • Clapp, C. E.
    • Dolan, M. S.
  • Source: Soil & Tillage Research
  • Volume: 89
  • Issue: 2
  • Year: 2006
  • Summary: Soil organic carbon (SOC) and nitrogen (N) are directly influenced by tillage, residue return and N fertilization management practices. Soil samples for SOC and N analyses, obtained from a 23-year field experiment, provided an assessment of near-equilibrium SOC and N conditions. Crops included corn (Zea mays L.) and soybean [Glycine max L. (Merrill)]. Treatments of conventional and conservation tillage, residue stover (returned or harvested) and two N fertilization rates were imposed on a Waukegan silt loam (fine-silty over skeletal, mixed, superactive, mesic Typic Hapludoll) at Rosemount, MN. The surface (0-20 cm) soils with no-tillage (NT) had greater than 30% more SOC and N than moldboard plow (MB) and chisel plow (CH) tillage treatments. The trend was reversed at 20-25 cm soil depths, where significantly more SOC and N were found in MB treatments (26 and 1.5 Mg SOC and N ha-1, respectively) than with NT (13 and 1.2 Mg SOC and N ha-1, respectively), possibly due to residues buried by inversion. The summation of soil SOC over depth to 50 cm did not vary among tillage treatments; N by summation was higher in NT than MB treatments. Returned residue plots generally stored more SOC and N than in plots where residue was harvested. Nitrogen fertilization generally did not influence SOC or N at most soil depths. These results have significant implications on how specific management practices maximize SOC storage and minimize potential N losses. Our results further suggest different sampling protocols may lead to different and confusing conclusions regarding the impact of tillage systems on C sequestration.
  • Authors:
    • McLaughlin, N. B.
    • Calder, W.
    • Welacky, T. W.
    • Tan, C. S.
    • Reynolds, W. D.
    • Drury, C. F.
  • Source: Soil Science Society of America Journal
  • Volume: 70
  • Issue: 2
  • Year: 2006
  • Summary: Innovative management practices are required to increase the efficiency of N fertilizer usage and to reduce nitrous oxide (N2O) and carbon dioxide (CO2) emissions from agricultural soils. The objectives of this study were to evaluate the feasibility of using conservation tillage and N fertilizer placement depth to reduce N2O and CO2 emissions associated with corn (Zea mays L.) production on clay loam soils in Eastern Canada. A 3-yr field study was established on a wheat (Triticum aestivum L.)-corn-soybean [Glycine max (L.) Merr.] rotation with each phase of the rotation present every year. Investigations were focused on the corn phase of the rotation. The tillage treatments following winter wheat included fall moldboard plow tillage (15 cm depth), fall zone-tillage (21 cm width, 15 cm depth), and no-tillage. The N placement treatments were "shallow" placement of sidedress N (2-cm depth) and "deep" placement of sidedress N (10-cm depth). Nitrous oxide emissions were measured 53 times and CO2 emissions were measured 43 times over three growing seasons using field-based sampling chambers. There was a significant tillage and N placement interaction on N2O emissions. Averaged over all three tillage systems and site-years, N2O emissions from shallow N placement (2.83 kg N ha-1 yr-1) were 26% lower than deep N placement (3.83 kg N ha-1 yr-1). The N2O emissions were similar among the tillage treatments when N was placed in the soil at a shallow depth. However, when N was placed deeper in the soil (10 cm), the 3-yr average N2O emissions from zone-tillage (2.98 kg N ha-1 yr-1) were 20% lower than from no-tillage (3.71 kg N ha-1 yr-1) and 38% lower than those from moldboard plow tillage (4.81 kg N ha-1 yr-1). Tillage type and N placement depth did not affect CO2 emissions (overall average = 5.80 Mg C ha-1 yr-1). Hence, zone-tillage and shallow N placement depth reduced N2O emissions without affecting CO2 emissions.
  • Authors:
    • Beegle, D. B.
    • Duiker, S. W.
  • Source: Soil & Tillage Research
  • Volume: 88
  • Issue: 1-2
  • Year: 2006
  • Summary: In permanent no-till (NT), soil nutrients are no longer mixed into the topsoil as with moldboard plow/disking (MD), whereas chisel/disking (CD) does limited mixing. Surface broadcast and/or banded nutrient applications may result in high and low fertility zones in permanent NT, with possible implications for soil sampling and nutrient placement.We investigated effects of 25 years of continuous NT, CD and MD with corn planted in the same row locations on organic matter (SOM), pH-H2O and Mehlich-3 extractable phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg). Vertical distribution at 0-5, 5-10 and 10-15 cm depths was measured as well as horizontal distributions across corn rows. We observed higher SOM and P in NT and CD than in MD in the 0-15 cm layer. SOM content was greatest in the top 5 cm in NT, but declined sharply with depth. SOM content in CD was not as high at the surface as in NT, but did not decline as fast as in NT. SOM was uniform but low throughout the 0-15 cm depth of MD. In all tillage systems, SOM did not vary across rows. Soil pH was higher in the 0-5 cm layer of NT than the deeper layers but the reverse was true in the CD or MD treatments. Concentrations of P, K and Ca were higher in the surface 0-5 cm than 10-15 cm depth of all tillage systems, but most strikingly in NT and CD. Starter fertilizer injection resulted in higher P and lower pH in the injection zone of all tillage treatments, but most notably in NT. The pH was depressed under the band of side-dressed nitrogen with all tillage systems. Potassium accumulated in the rows of the previous crop, probably because it leached from crop residue that accumulated there. Tillage did not affect Mg distribution. Optimal nutrient management in NT should take account of horizontal and vertical nutrient and pH distributions. Samples in long-term NT could potentially be taken to a shallower depth if calibration curves are available. To avoid underestimating P and K availability or overestimate lime needs, high P or decreased pH bands should be avoided, as well as crop rows. Possibilities to reduce P and K applications with banding need more investigation. Results show the importance of regular liming in NT to maintain surface pH in the optimum range, but also show that lime does not have to be incorporated.
  • Authors:
    • Caswell, M.
    • Fernandez-Cornejo, J.
  • Source: Economic Information Bulletin Number 11
  • Volume: 11
  • Year: 2006