• Authors:
    • Hons, F.
    • Dou, F.
    • Wright, A.
  • Source: Soil Science
  • Volume: 172
  • Issue: 2
  • Year: 2007
  • Summary: Crop species and conservation tillage may enhance carbon (C) and nitrogen (N) sequestration potential in subsurface soils. The objectives of this study were to determine the effects of crop species and tillage on soil organic C (SOC) and total N distribution in six soil depth intervals from 0 to 105 cm after 20 years of treatment imposition. Tillage had the most influence on soil C and N at 0 to 5 cm, and impacts extended to the 15- to 30-cm depth for wheat and sorghum. Overall, SOC and total N for wheat were 18 and 15% higher than sorghum and soybean. Dissolved organic C (DOC) depth distribution was similar to SOC and total N. The proportion of SOC as DOC ranged from 1.3 to 3.3% and increased with soil depth. The highest soil C and N levels occurred for wheat under no tillage. The depth of soil impacted by crop species was shallower for conventional tillage than no tillage, and the depth distribution exhibited a logarithmic pattern. Soil organic C, total N, and DOC decreased 404, 507, and 205%, respectively from 0-5 to 80-105 cm. The maximum depth interval below which no further decreases in SOC and total N occurred was 30 to 55 cm for soybean, 55 to 80 cm for wheat, and 80 to 105 cm for sorghum, demonstrating the importance of subsurface soils for C sequestration. Crop management impacts below the depth of tillage demonstrate the importance of crop rooting and belowground biomass, or translocation of dissolved organic matter, to subsoil C sequestration.
  • Authors:
    • Lares, M. T.
    • Liebig, M. A.
    • Merrill, S. D.
    • Tanaka, D. L.
    • Krupinsky, J. M.
    • Hanson, J. D.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 4
  • Year: 2007
  • Summary: Crop sequence is an important management practice that may lower the risk for leaf spot diseases of spring wheat ( Triticum aestivum L.). Field research was conducted near Mandan, ND, to determine the impact of crop sequences on leaf spot diseases of hard red spring wheat early in the growing season. Spring wheat was evaluated for disease severity following crop sequence combinations of 10 crops [buckwheat ( Fagopyrum esculentum Moench)], canola ( Brassica napus L.), chickpea ( Cicer arietinum L.), corn ( Zea mays L.), dry pea ( Pisum sativum L.), grain sorghum [ Sorghum bicolor (L.) Moench], lentil ( Lens culinaris Medik.), oil seed sunflower ( Helianthus annuus L.), proso millet ( Panicum miliaceum L.), and hard red spring wheat. Spring wheat leaves with distinct lesions were collected for determination of lesion number and percentage necrosis data, which were used to estimate leaf spot disease severity. Pyrenophora tritici-repentis (Died.) Drechs., the cause of tan spot, and Phaeosphaeria nodorum (E. Muller) Hedjaroude, the cause of Stagonospora nodorum blotch, were the major leaf spot diseases and consistently present throughout the growing season. The frequency of isolation following alternative crops was generally lower compared with spring wheat following wheat. Leaf spot diseases on spring wheat were impacted by crop sequencing. Spring wheat following crop sequences with alternative crops for 1 or 2 yr had lower levels of disease severity compared with a continuous spring wheat treatment early in the growing season. Disease severity was apparently not related to the percentage of crop residue coverage on the soil surface associated with various crop sequence combinations. New alternative crops preceding spring wheat reduce levels of leaf spot diseases.
  • Authors:
    • Six, J.
    • West, T. O.
  • Source: Climatic Change
  • Volume: 80
  • Issue: 1
  • Year: 2007
  • Summary: Rates of soil C sequestration have previously been estimated for a number of different land management activities, and these estimates continue to improve as more data become available. The time over which active sequestration occurs may be referred to as the sequestration duration. Integrating soil C sequestration rates with durations provides estimates of potential change in soil C capacity and more accurate estimates of the potential to sequester C. In agronomic systems, changing from conventional plow tillage to no-till can increase soil C by an estimated 16 ± 3%, whereas increasing rotation intensity can increase soil C by an estimated 6 ± 3%. The increase in soil C following a change in rotation intensity, however, may occur over a slightly longer period (26 yr) than that for tillage cessation (21 yr). Sequestration strategies for grasslands have, on average, longer sequestration durations (33 yr) than for croplands. Estimates for sequestration rates and durations are mean values and can differ greatly between individual sites and management practices. As the annual sequestration rate declines over the sequestration duration period, soil C approaches a new steady state. Sequestration duration is synonymous with the time to which soil C steady state is reached. However, soils could potentially sequester additional C following additional changes in management until the maximum soil C capacity, or soil C saturation, is achieved. Carbon saturation of the soil mineral fraction is not well understood, nor is it readily evident. We provide evidence of soil C saturation and we discuss how the steady state C level and the level of soil C saturation together influence the rate and duration of C sequestration associated with changes in land management.
  • Authors:
    • Lightle, D. T.
    • Karlen, D. L.
    • Johnson, J. M. F.
    • Wilhelm, W. W.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 6
  • Year: 2007
  • Summary: Sustainable aboveground crop biomass harvest estimates for cellulosic ethanol production, to date, have been limited by the need for residue to control erosion. Recently, estimates of the amount of corn (Zea mays L.) stover needed to maintain soil carbon, which is responsible for favorable soil properties, were reported (5.25-12.50 Mg ha-1). These estimates indicate stover needed to maintain soil organic carbon, and thus productivity, are a greater constraint to environmentally sustainable cellulosic feedstock harvest than that needed to control water and wind erosion. An extensive effort is needed to develop advanced cropping systems that greatly expand biomass production to sustainably supply cellulosic feedstock without undermining crop and soil productivity.
  • Authors:
    • Chameides, B.
    • Willey, Z.
  • Source: The Nicholas Institute for Environmental Policy Solutions
  • Year: 2007
  • Authors:
    • Ascough, J. C.,II
    • McMaster, G. S.
    • Andales, A. A.
    • Hansen, N. C.
    • Sherrod, L. A.
  • Source: Transactions of the ASABE
  • Volume: 50
  • Issue: 5
  • Year: 2007
  • Summary: Alternative agricultural management systems in the semi-arid Great Plains are receiving increasing attention. GPFARM is a farm/ranch decision support system (DSS) designed to assist in strategic management planning for land units from the field to the whole-farm level. This study evaluated the regional applicability and efficacy of GPFARM based on simulation model performance for dry mass grain yield, total soil profile water content, crop residue, and total soil profile residual NO 3-N across a range of dryland no-till experimental sites in eastern Colorado, USA. Field data were collected from 1987 through 1999 from an on-going, long-term experiment at three locations in eastern Colorado along a gradient of low (Sterling), medium (Stratton), and high (Walsh) potential evapotranspiration. Simulated crop alternatives were winter wheat ( Triticum aestivum), maize ( Zea mays), sorghum ( Sorghum bicolor), proso millet ( Panicum miliaceum), and fallow. Relative error (RE) of simulated mean, root mean square error (RMSE), and index of agreement (d) model evaluation statistics were calculated to compare modelled results to measured data. A one-way, fixed-effect ANOVA was also performed to determine differences among experimental locations. GPFARM simulated versus observed REs ranged from -3 to 35% for crop yield, 6 to 8% for total soil profile water content, -4 to 32% for crop residue, and -7 to -25% for total soil profile residual NO 3-N. For trend analysis (magnitudes and location differences), GPFARM simulations generally agreed with observed trends and showed that the model was able to simulate location differences for the majority of model output responses. GPFARM appears to be adequate for use in strategic planning of alternative cropping systems across eastern Colorado dryland locations; however, further improvements in the crop growth and environmental components of the simulation model (including improved parameterization) would improve its applicability for short-term tactical planning scenarios.
  • Authors:
    • Wohlgenant, M.
    • Zering, K.
  • Year: 2007
  • Authors:
    • Arkebauer, T. J.
    • Grant, R. F.
    • Dobermann, A.
    • Hubbard, K. G.
    • Schimelfenig, T. T.
    • Verma, S. B.
    • Suyker, A. E.
    • Walters, D. T.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 6
  • Year: 2007
  • Summary: Estimates of agricultural C sequestration require an understanding of how net ecosystem productivity (NEP) and net biome productivity (NBP) are affected by land use. Such estimates will most likely be made using mathematical models that have undergone well-constrained tests against field measurements of CO 2 exchange as affected by management. We tested a hydraulically driven soil-plant-atmosphere C and water transfer scheme in ecosys against CO 2 and energy exchange measured by eddy covariance (EC) over irrigated and rainfed no-till maize-soybean rotations at Mead, NE. Correlations between modeled and measured fluxes ( R2>0.8) indicated that <20% of variation in EC fluxes could not be explained by the model. Annual aggregations of modeled fluxes indicated that NEP of irrigated and rainfed soybean in 2002 was -30 and -9 g C m -2 yr -1 (net C source) while NEP of irrigated and rainfed maize in 2003 was 615 and 397 g C m -2 yr -1 (net C sink). These NEPs were within the range of uncertainty in annual NEP estimated from gap-filled EC fluxes. When grain harvests were subtracted from NEP to calculate NBP, both the modeled and measured maize-soybean rotations became net C sources of 40 to 80 g C m -2 yr -1 during 2002 and 2003. Long-term model runs (100 yr) under repeated 2001-2004 weather sequences indicated that a rainfed no-till maize-soybean rotation at Mead would lose about 30 g C m -2 yr -1. Irrigating this rotation would raise SOC by an average of 6 g C m -2 yr -1 over rainfed values. Modeled and measured results indicated only limited opportunity for long-term soil C storage in irrigated or rainfed maize-soybean rotations under the soil, climate, and management typical of intensive crop production in the U.S. Midwest.
  • Authors:
    • Reule, C. A.
    • Halvorson, A. D.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 6
  • Year: 2007
  • Summary: Converting irrigated, conventional-till (CT) systems to no-till (NT) production systems can potentially reduce soil erosion, fossil fuel consumption, and greenhouse gas emissions. Nitrogen fertilization effects on irrigated corn (Zea mays L.) and malting barley (Hordeum distichon L.) yields in a corn-barley rotation were evaluated for 6 yr on a clay loam soil to determine the viability of using a NT system and N needs for optimum crop yield. Six N treatments were established with N rates varying from 0 to 224 kg N ha(-1) for corn and 0 to 1.12 kg N ha(-1) for barley. Corn and barley grain yields were significantly increased by N fertilization each of 3 yr in the rotation. Three year average corn grain yields were near maximum with an available N (AN) (soil + fertilizer + irrigation water N) level of 274 kg N ha(-1). Barley yields increased linearly with increasing N rate with grain protein content near 130 kg protein Mg-1 grain at the highest N rate. Nitrogen use efficiency (NUE) by corn and barley, based on grain N removal, decreased with increasing AN level and ranged from 204 to 39 and 68 to 31 kg grain kg(-1) AN for the low and high N treatments for corn and barley, respectively. Total plant N uptake required to produce one Mg grain at near maximum yield in this study averaged 21 kg N for corn and 27 kg N for barley. Corn and barley residue production increased with increasing N rate. Irrigated, NT corn yields obtained in this corn-barley rotation were acceptable (>10 Mg ha(-1)) for northern Colorado; however, barley yields did not meet our expected yield goal of 5.4 Mg ha(-1) with the N rates used in this study, but grain protein was near maximum for malting barley. An irrigated, NT corn-barley production system appears to be feasible in northern Colorado.
  • Authors:
    • Donnarummo, M. G.
    • Castiglioni, P. P.
    • Bensen, R. J.
    • Anstrom, D. C.
    • Warner, D. C.
    • Wu, J.
    • Creelman, R. A.
    • Adams, T. R.
    • Repetti, P. P.
    • Nelson, D. E.
  • Source: PNAS: Proceedings of the National Academy of Sciences
  • Volume: 104
  • Issue: 42
  • Year: 2007
  • Summary: Commercially improved crop performance under drought conditions has been challenging because of the complexity of the trait and the multitude of factors that influence yield. Here we report the results of a functional genomics approach that identified a transcription factor from the nuclear factor Y (NF-Y) family, AtNF-YB1, which acts through a previously undescribed mechanism to confer improved performance in Arabidopsis under drought conditions.