• Authors:
    • Robertson, G. P.
    • Kravchenko, A. N.
    • Senthilkumar, S.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 6
  • Year: 2009
  • Summary: Topography is one of the major factors affecting sod C and N contents at the field/landscape level. However, topographical effects are likely to differ in magnitude in different agricultural systems. The objective of this study was to examine the interactions between topography and management systems on Soil C and N. The study was conducted at the Kellogg Biological Station Long-Term Ecological Research (LTER) site in southwest Michigan. The studied treatments were chisel-plow (CT) and no-till (NT) with conventional chemical inputs and a chisel-plow organic management system with winter leguminous cover crops (CT-cover). At the 0- to 5-cm depth in both upperslope and valley positions total C and N contents of NT management were the highest followed by CT-cover and then CT At 0- to 15-, 20- to 30-, and 30- to 40-cm depths, treatment effects varied depending on the landscape position. There were no differences among the treatments in upperslopes, while in the valleys total C and N tended to be the highest in NT and CT-cover followed by CT. The results indicated the importance of accounting for interaction between topography and management practices when assessing C sequestration across landscapes with varying topography. Total C stocks at the 0- to 30-cm depths were around 35,32, and 27 MgC ha(-1) soil (+/- 2 MgC ha(-1) standard error) in CT-cover, NT and CT respectively, across upperslopes and valleys. Overall, CT-cover was found to be as efficient in maintaining C and N content as no-till with conventional chemical inputs. Power analysis for C and N stocks at the 0- to 40-cm depth revealed that because of high variability in total C and N stocks at greater depths, the 10 to 30 samples per treatment available in this study were inadequate to detect differences in C and N stocks if the differences were < 26 MgC ha(-1).
  • Authors:
    • Bosque-Pérez, N. A.
    • Eigenbrode, S. D.
    • Hatten, T. D.
    • Johnson-Maynard, J. L.
    • Umiker, K. J.
  • Source: Soil & Tillage Research
  • Volume: 105
  • Issue: 2
  • Year: 2009
  • Summary: Farmers within the Inland Pacific Northwest are gradually transitioning to direct seed (DS) practices that reduce soil disturbance and increase surface residue compared to conventional tillage (CT). Despite this transition the impacts of DS practices on soil properties and fauna in commercial fields has been little studied in the region. During the spring and summer of 2002 and 2003 we compared soil organic carbon (SOC), total nitrogen (TN), pH, and earthworm and cocoon densities in CT and DS fields planted to either spring wheat or pea in the Palouse region of northern Idaho. In 2002 mean SOC within the 0-10-cm depth was greater in DS fields (2.05%) than at the same depth in CT fields (1.79%), however SOC within the 30-40-cm depth was lower under DS compared to CT. Mean soil pH within the 0-10-cm depth was 5.35 under DS and 5.61 under CT indicating that pH stratification can occur when tillage is reduced. Tillage effects on SOC, TN, and pH were not found in 2003. Tillage also did not significantly influence earthworm densities, which averaged 39 individuals m-2 in 2002 and 57 individuals m-2 in 2003. Correlations were detected in 2003 DS fields between soil properties (SOC and TN) and earthworm and cocoon densities at depths above 30 cm while in 2002 correlations in DS fields occurred with cocoon density, but not with earthworm density. Direct seed management can increase near-surface SOC and TN concentrations compared to CT practices, however, SOC concentrations deeper in the soil appear to remain the same or possibly decrease. Higher SOC and TN near the soil surface, as found in DS fields, appear to promote greater earthworm densities, which may improve long-term soil productivity.
  • Authors:
    • USDA
  • Year: 2009
  • Authors:
    • Jarecki, M. K.
    • Lal, R.
    • Ussiri, D. A. N.
  • Source: Soil & Tillage Research
  • Volume: 104
  • Issue: 2
  • Year: 2009
  • Summary: Nitrous oxide (N2O) and methane (CH4) emitted by anthropogenic activities have been linked to the observed and predicted climate change. Conservation tillage practices such as no-tillage (NT) have potential to increase C sequestration in agricultural soils but patterns of N2O and CH4 emissions associated with NT practices are variable. Thus, the objective of this study was to evaluate the effects of tillage practices on N2O and CH4 emissions in long-term continuous corn (Zea mays) plots. The study was conducted on continuous corn experimental plots established in 1962 on a Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf) in Ohio. The experimental design consisted of NT, chisel till (CT) and moldboard plow till (MT) treatments arranged in a randomized block design with four replications. The N2O and CH4 fluxes were measured for 1-year at 2-week intervals during growing season and at 4-week intervals during the off season. Long-term NT practice significantly decreased soil bulk density (rho(b)) and increased total N concentration of the 0-15 cm layer compared to MT and CT. Generally, NT treatment contained higher soil moisture contents and lower soil temperatures in the surface soil than CT and MT during summer, spring and autumn. Average daily fluxes and annual N2O emissions were more in MT (0.67 mg m(-2) d(-1) and 1.82 kg N ha(-1) year(-1)) and CT (0.74 mg m(-2) d(-1) and 1.96 kg N ha(-1) year(-1)) than NT (0.29 mg m(-2) d(-1) and 0.94 kg N ha(-1) year(-1)). On average, NT was a sink for CH4, oxidizing 0.32 kg CH4-C ha(-1) year(-1), while MT and CT were sources of CH4 emitting 2.76 and 2.27 kg CH4-C ha(-1) year(-1), respectively. Lower N2O emission and increased CH4 oxidation in the NT practice are attributed to decrease in surface rho(b), suggesting increased gaseous exchange. The N2O flux was strongly correlated with precipitation, air and soil temperatures, but not with gravimetric moisture content. Data from this study suggested that adoption of long-term NT under continuous corn cropping system in the U.S. Corn Belt region may reduce GWP associated with N2O and CH4 emissions by approximately 50% compared to MT and CT management.
  • Authors:
    • VandenBygaart, A. J.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 4
  • Year: 2009
  • Summary: Comments on "Regional study of no-till effects on carbon sequestration in the Midwestern United States"
  • Authors:
    • Institute for the Study of Earth, Oceans and Space
  • Year: 2009
  • Summary: The DNDC model is a process-base model of carbon (C) and nitrogen (N) biogeochemistry in agricultural ecosystems. This document describes how to use the PC Windows versions of the DNDC model for predicting crop yield, C sequestration, nitrate leaching loss, and emissions of C and N gases in agroecosystems. Part I provides a brief description of the model structure with relevant scientific basis. Part II describes how to install the model. Part III and IV demonstrate how to conduct simulations with the site and regional versions of DNDC, respectively. Part V provides basic information for uncertainty analysis with DNDC. Part VI contains six case studies demonstrating the input procedures for simulating crop yield, soil C dynamics, nitrate leaching loss, and trace gas emissions. A list of relevant publications is included in Part VII. These publications provide more information about the scientific background and applications of DNDC far beyond this User's Guide. DNDC9.3 can run in two modes: site or regional. By selecting the mode, the users will open a corresponding interface to manage their input information for the modeled site or region.
  • Authors:
    • Six, J.
    • van Kessel, C.
    • Fonte, S. J.
    • Kong, A. Y. Y.
  • Source: Soil & Tillage Research
  • Volume: 104
  • Issue: 2
  • Year: 2009
  • Summary: Few studies address nutrient cycling during the transition period (e.g., 1-4 years following conversion) from standard to some form of conservation tillage. This study compares the influence of minimum versus standard tillage on changes in soil nitrogen (N) stabilization, nitrous oxide (N2O) emissions, short-term N cycling, and crop N use efficiency 1 year after tillage conversion in conventional (i.e., synthetic fertilizer-N only), low-input (i.e., alternating annual synthetic fertilizer- and cover crop-N), and organic (i.e., manure- and cover crop-N) irrigated, maize-tomato systems in California. To understand the mechanisms governing N cycling in these systems, we traced N-15-labeled fertilizer/cover crop into the maize grain, whole soil, and three soil fractions: macroaggregates (>250 mu m), microaggregates (53-250 mu m) and silt-and-clay (<53 mu m). We found a cropping system effect on soil N-new (i.e., N derived from N-15-fertilizer or - N-15-cover crop), with 173 kg N-new ha(-1) in the conventional system compared to 71.6 and 69.2 kg N-new ha(-1) in the low-input and organic systems, respectively. In the conventional system, more N-new was found in the microaggregate and silt-and-clay fractions, whereas, the N-new of the organic and low-input systems resided mainly in the macroaggregates. Even though no effect of tillage was found on soil aggregation, the minimum tillage systems showed greater soil fraction-N-new than the standard tillage systems, suggesting greater potential for N stabilization under minimum tillage. Grain-N-new was also higher in the minimum versus standard tillage systems. Nevertheless, minimum tillage led to the greatest N2O emissions (39.5 g (NO)-O-2-N ha(-1) day(-1)) from the conventional cropping system, where N turnover was already the fastest among the cropping systems. In contrast, minimum tillage combined with the low-input system (which received the least N ha(-1)) produced intermediate N2O emissions, soil N stabilization, and crop N use efficiency. Although total soil N did not change after 1 year of conversion from standard to minimum tillage, our use of stable isotopes permitted the early detection of interactive effects between tillage regimes and cropping systems that determine the trade-offs among N stabilization, N2O emissions, and N availability. (C) 2009 Elsevier B.V. All rights reserved.
  • Authors:
    • Moreno, F.
    • Murillo, J. M.
    • López-Garrido, R.
    • Melero, S.
  • Source: Soil & Tillage Research
  • Volume: 104
  • Issue: 2
  • Year: 2009
  • Summary: Short- and long-term field experiments are necessary to provide important information about how soil carbon sequestration is affected by soil tillage system; such systems can also be useful for developing sustainable crop production systems. In this study, we evaluated the short- and long-term effects of conservation tillage (CT) on soil organic carbon fractions and biological properties in a sandy clay loam soil. Both trials consisted of rainfed crop rotation systems (cereal-sunflower-legumes) located in semi-arid SW Spain. In both trials, results were compared to those obtained using traditional tillage (TT). Soil samples were taken in flowering and after harvesting of a pea crop and collected at three depths (0-5, 5-10 and 10-20 cm). The soil organic carbon fractions were measured by the determination of total organic carbon (TOC), active carbon (AC) and water soluble carbon (WSC). Biological status was evaluated by the measurement of soil microbial biomass carbon (MBC) and enzymatic activities [dehydrogenase activity (DHA), o-diphenol oxidase activity (DphOx), and beta-glucosidase activity (beta-glu)]. The contents of AC and MBC in the long-term trial and contents of AC in the short-term trial were higher for CT than TT at 0-5 cm depth for both sampling periods. Furthermore, DHA and beta-glucosidase values in the July sampling were higher in the topsoil under conservation management in both trials (short- and long-term). The parameters studied tended to decrease as depth increased for both tillage system (TT and CT) and in both trials with the exception of the DphOx values, which tended to be higher at deeper layers. Values of DHA and beta-glu presented high correlation coefficients (r from 0.338 to 0.751, p <= 0.01) with AC, WSC and TOC values in the long-term trial. However, there was no correlation between either TOC or MBC and the other parameters in the short-term trial. In general, only stratification ratios of AC were higher in CT than in TT in both trials. The results of this study showed that AC content was the most sensitive and reliable indicator for assessing the impact of different soil management on soil quality in the two experiments (short- and long-term). Conservation management in dryland farming systems improved the quality of soil under our conditions, especially at the surface layers, by enhancing its storage of organic matter and its biological properties, mainly to long-term. (C) 2009 Elsevier B.V. All rights reserved.
  • Authors:
    • Jordan, D.
    • Owen, M. D. K.
    • Wilson, R. G.
    • Young, B. G.
    • Weller, S. C.
    • Johnson, W. G.
    • Kruger, G. R.
    • Shaw, D. R.
    • Givens, W. A.
  • Source: Weed Technology
  • Volume: 23
  • Issue: 1
  • Year: 2009
  • Summary: A phone survey was administered to 1,195 growers in six states (Illinois, Indiana, Iowa, Mississippi, Nebraska, and North Carolina). The survey measured producers' crop history, perception of glyphosate-resistant (GR) weeds, past and present weed pressure, tillage practices, and herbicide use as affected by the adoption of GR crops. This article describes the changes in tillage practice reported in the survey. The adoption of a GR cropping system resulted in a large increase in the percentage of growers using no-till and reduced-till systems. Tillage intensity declined more in continuous GR cotton and GR soybean (45 and 23%, respectively) than in rotations that included GR corn or non-GR crops. Tillage intensity declined more in the states of Mississippi and North Carolina than in the other states, with 33% of the growers in these states shifting to more conservative tillage practices after the adoption of a GR crop. This was primarily due to the lower amount of conservation tillage adoption in these states before GR crop availability. Adoption rates of no-till and reduced-till systems increased as farm size decreased. Overall, producers in a crop rotation that included a GR crop shifted from a relatively more tillage-intense system to reduced-till or no-till systems after implementing a GR crop into their production system.
  • Authors:
    • Alberta Environment
  • Year: 2009
  • Summary: The opportunity for generating carbon offsets with this protocol arises from the direct and indirect reductions of greenhouse gas (GHG) emissions through implementing no-till and reduced till systems on agricultural lands.