• Authors:
    • Anderson, R. L.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 25
  • Issue: 3
  • Year: 2010
  • Summary: Weeds are a major obstacle to successful crop production in organic farming. Producers may be able to reduce inputs for weed management by designing rotations to disrupt population dynamics of weeds. Population-based management in conventional farming has reduced herbicide use by 50% because weed density declines in cropland across time. In this paper, we suggest a 9-year rotation comprised of perennial forages and annual crops that will disrupt weed population growth and reduce weed density in organic systems. Lower weed density will also improve effectiveness of weed control tactics used for an individual crop. The rotation includes 3-year intervals of no-till, which will improve both weed population management and soil health. Even though this rotation has not been field tested, it provides an example of designing rotations to disrupt population dynamics of weeds. Also, producers may gain additional benefits of higher crop yield and increased nitrogen supply with this rotation design.
  • Authors:
    • Caesar-TonThat, T.
    • Wright, S. F.
    • Sainju, U. M.
    • Kolberg, R.
    • West, M.
  • Source: Proceedings of the 19th World Congress of Soil Science: Soil solutions for a Changing World, Brisbane, Australia, 1-6 August 2010. Congress Symposium 2: Soil ecosystem services
  • Year: 2010
  • Summary: Lentil ( Lens culinaris Medikus CV. Indianhead) used to replace fallow in spring-wheat ( Triticum aestivum) rotation in the semi-arid Eastern Montana USA, may improve soil quality. We evaluate the 14 years influence of continuous wheat under no-tillage (WNT), fallow-wheat under conventional tillage (FCT) and no-tillage (FNT), lentil-wheat under tillage (LCT) and no-tillage (LNT) on soil formation and stability, and on the amount of immunoreactive easily-extractable glomalin (IREEG) and soil aggregating basidiomycete fungi in the 4.75-2.00, 2.00-1.00, 1.00-0.50, 0.50-0.25, and 0.25-0.00 mm aggregate-size classes, at 0-5 cm soil depth. The 4.75-2.00 mm aggregate proportion was higher in LNT than FNT and higher in LT than FT treatments and mean weight diameter (MWD) was higher when lentil was used to replace fallow under NT. No-till systems had higher glomalin and basidiomycete amount than CT in all aggregate-size classes and glomalin was higher in LNT than FNT in aggregate-size classes less than 0.50 mm. We conclude that residue input in NT systems triggers fungal populations which are involved in soil binding in aggregates, and that replacing fallow by lentil in spring wheat rotation in dryland seems to favor aggregate formation/stability under NT probably by increasing N fertility during the course of 14 years.
  • Authors:
    • Schlegel, A. J.
    • Stone, L. R.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 2
  • Year: 2010
  • Summary: Efficient water use is the primary determinant of profitability in dryland crop production of the western Great Plains. For a sustainable increase in precipitation use efficiency (PUE) from that typical of the traditional winter wheat (Triticum aestivum L.)-fallow rotation with conventional stubble-mulch (sweep) tillage (CT) to occur, decreased use of fallow and tillage is required. Our objective was to quantify the effect of tillage intensity (no-till [NT], reduced tillage [RT], and CT) and phase of the winter wheat-grain sorghum [Sorghum bicolor (L.) Moench]-fallow rotation on selected sod properties that influence PUE, with emphasis on infiltration and the association between water-stable aggregates (WSA) and infiltration rate. Soil water content at -1.5 MPa matric potential, concentration of WSA >= 0.5 mm, mean weight diameter of WSA, and ponded steady-state infiltration rate were significantly greater with NT than RT or CT (infiltration rates: NT, 30.6; RT, 15.3; and CT, 11.4 mm h(-1)). Infiltration rate was significantly greater in the wheat phase (25.8 mm h(-1)) than in the sorghum (15.4 mm h(-1)) or fallow (16.2 mm h(-1)) phases. The significantly better conditions of aggregate stability and water infiltration with NT management and the lack of development of poor infiltration properties during the wheat season that would need to be alleviated by tillage after harvest reinforce the appropriateness of NT management in crop production systems of the region.
  • Authors:
    • van Groenigen, K. J.
    • van Kessel, C.
    • Oenema, O.
    • Velthof, G. L.
    • van Groenigen, J. W.
  • Source: European Journal of Soil Science
  • Volume: 61
  • Issue: 6
  • Year: 2010
  • Summary: Agricultural soils are the main anthropogenic source of nitrous oxide (N2O), largely because of nitrogen (N) fertilizer use. Commonly, N2O emissions are expressed as a function of N application rate. This suggests that smaller fertilizer applications always lead to smaller N2O emissions. Here we argue that, because of global demand for agricultural products, agronomic conditions should be included when assessing N2O emissions. Expressing N2O emissions in relation to crop productivity (expressed as above-ground N uptake: "yield-scaled N2O emissions") can express the N2O efficiency of a cropping system. We show how conventional relationships between N application rate, N uptake and N2O emissions can result in minimal yield-scaled N2O emissions at intermediate fertilizer-N rates. Key findings of a meta-analysis on yield-scaled N2O emissions by non-leguminous annual crops (19 independent studies and 147 data points) revealed that yield-scaled N2O emissions were smallest (8.4 g N2O-N kg-1N uptake) at application rates of approximately 180-190 kg Nha-1 and increased sharply after that (26.8 g N2O-N kg-1 N uptake at 301 kg N ha-1). If the above-ground N surplus was equal to or smaller than zero, yield-scaled N2O emissions remained stable and relatively small. At an N surplus of 90 kg N ha-1 yield-scaled emissions increased threefold. Furthermore, a negative relation between N use efficiency and yield-scaled N2O emissions was found. Therefore, we argue that agricultural management practices to reduce N2O emissions should focus on optimizing fertilizer-N use efficiency under median rates of N input, rather than on minimizing N application rates.
  • Authors:
    • Kutcher, H. R.
    • Kryzanowski, L. M.
  • Source: Recent Trends in Soil Science and Agronomy Research in the Northern Great Plains of North America
  • Year: 2010
  • Summary: Variability in soil and crop productivity in the Northern Great Plains is related to the pedogenic development of the parent glacial deposits, climate, native vegetation, and topography. Anthropogenic field management over the past 100 years has contributed to additional field variability through tillage erosion, crop-fallow rotations, fertilizer management, livestock manure management and crop residue management. Field topography influences microclimate and the hydrological conditions within a landscape by the redistribution of water and soil thermal dynamics. Water movement from upper to lower slope and depression areas either by runoff or through subsoil will result in the physical redistribution of surface soil (erosion), translocation of soluble nutrients or accumulation of salts. The end result of this redistribution is drier warmer upper slopes, and wetter cooler lower slopes and depressions. This influences soil biological, chemical and physical processes that impact crop growth. Often, the lowest crop yields are measured on the upper slopes and the highest yields on the lower slopes. Upper slopes are prone to erosion, shallow surface horizons, higher carbonate levels, lower organic matter levels and lower available water. The lower slopes have deposits of eroded surface material, deeper surface horizons, greater depth to carbonates, higher organic matter levels and higher available water. However, spatial relationships between productivity and landscape position are not always consistent. Higher productivity does not always occur in lower slopes because yield reductions can occur as a result of planting delays, poor crop germination, poor soil aeration, poor drainage, poor root development, foliar and root diseases, compaction, nutrient deficiencies, weed competition, limited root development, stunted crop development, acidic soil and salinity. Precision farming provides an opportunity to utilize technology to manage the topographical and spatial variability. Elevation and positioning data collected from global positioning systems can be managed by means of geographic information systems. Landform segmentation provides a fundamental basis for subdividing fields into landscape management units based on topography. Field sensors such as crop yield monitors along with remote sensing, aerial photography, soil sampling and weed populations provide additional data layers needed for site specific management. Variable rate controllers provide the technology for fertilizer, manure, lime and herbicide applications. Ultimately, economics will determine the adoption of precision farming technology and practices.
  • Authors:
    • López-Bellido, L.
    • López-Bellido, F. J.
    • Fontán, J. M.
    • López-Bellido, R. J.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 1
  • Year: 2010
  • Summary: Our objective was to determine the effect of tillage system, crop rotation, and N fertilization on soil organic carbon (SOC) storage in the 0- to 90-cm profile in a long-term (20-yr) experiment established in 1986 on a rainfed Mediterranean Vertisol in southern Spain. The treatments studied were: conventional tillage (CT) vs. no-tillage (NT); five crop rotations: wheat (Triticum aestivum L.)-chickpea (Cicer arietinum L.) (WC), wheat-sunflower (Helianthus annuus L.) (WS), wheat-bare fallow (WF), wheat-faba-bean (Vicia faba L.) (WFB), and continuous wheat (WW); and N fertilizer applied at four rates (0, 50, 100, and 150 kg N ha(-1)). The SOC content of soil samples was determined in 1995,1997,2000,2003, and 2006 for four different soil layers (0-15, 15-30, 30-60, and 60-90 cm). The application of N fertilizer did not influence SOC sequestration. The other treatments showed a gradual increase of total SOC content over time, although there were no differences between some consecutive years. The SOC accumulation was higher for 30- to 60- and 60- to 90-cm depths than other depths due to characteristic cracks of Vertisol. Over the 20 yr of the study, WW and WFB sequestered 21 and 15 Mg C ha(-1) more under NT than under CT, respectively. The other crop rotations did not show any difference in C sequestration between NT and CT. Under CT, WS sequestered more SOC than other rotations, while under NT, WW and WFB sequestered more SOC. In general, the crop rotation intensification and NT had a positive effect over time on SOC sequestration in this rainfed Mediterranean Vertisol.
  • Authors:
    • Alluvione, F.
    • Del Grosso, S. J.
    • Halvorson, A. D.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: Nitrogen fertilization is essential for optimizing crop yields; however, it increases N2O emissions. The study objective was to compare N2O emissions resulting from application of commercially available enhanced-efficiency N fertilizers with emissions from conventional dry granular urea in irrigated cropping systems. Nitrous oxide emissions were monitored from corn (Zea mays L.) based rotations receiving fertilizer rates of 246 kg N ha-1 when in corn, 56 kg N ha-1 when in dry bean (Phaseolus vulgaris L.), and 157 kg N ha-1 when in barley (Hordeum vulgare L. ssp. vulgare). Cropping systems included conventional-till continuous corn (CT-CC), no-till continuous corn (NT-CC), no-till corn-dry bean (NT-CDb), and no-till corn-barley (NT-CB). In the NT-CC and CT-CC systems, a controlled-release, polymer-coated urea (ESN) and dry granular urea were compared. In the NT-CDb and NT-CB rotations, a stabilized urea source (SuperU) was compared with urea. Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. Cumulative growing season N2O emissions from urea and ESN application were not different under CT-CC, but ESN reduced N2O emissions 49% compared with urea under NT-CC. Compared with urea, SuperU reduced N2O emissions by 27% in dry bean and 54% in corn in the NT-CDb rotation and by 19% in barley and 51% in corn in the NT-CB rotation. This work shows that the use of no-till and enhanced-efficiency N fertilizers can potentially reduce N2O emissions from irrigated systems.
  • Authors:
    • Mikha,M. M.
    • Nielsen,D. C.
    • Halvorson,A. D.
    • Benjamin,J. G.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 3
  • Year: 2010
  • Summary: Crop biomass has been proposed as a source stock for bioethanol production. Levels of crop residue removal must be determined to prevent degradation of soil physical and chemical properties resulting from soil organic carbon (SOC) loss. Carbon inputs from crop residues and an estimate of inputs from roots and rhizodeposition (C return) were calculated and compared with changes in SOC after seven cropping seasons at Akron, CO. Tillage treatments included a chisel plow (CP) and a no-till (NT) treatment. A crop rotation alternating grasses and broadleaf crops was compared with continuous corn ( Zea mays L.). Irrigation treatments included water application to meet evapotranspiration demand or application only during the reproductive stage of each crop. Total C return varied from 25 Mg ha -1 for the delayed irrigation, crop rotation plots to 63 Mg ha -1 for the fully irrigated, continuous corn plots. The change in SOC in the surface 30 cm of soil varied from -0.8 Mg SOC ha -1 for the rotation plots to a gain of 2.8 Mg ha -1 for the continuous corn plots after 7 yr. Correlating crop residue input with change in SOC showed that about 4.6 Mg ha -1 yr -1 C return is needed to maintain SOC levels for NT cropping systems and an average of 7.4 Mg ha -1 yr -1 C return is needed to maintain SOC levels under chisel tillage. Continuous corn was the only system that consistently provided sufficient crop residue to maintain SOC levels. Residue removal for off-farm use should consider only amounts that can be harvested without decreasing SOC levels.
  • Authors:
    • Sohngen, B.
    • Choi, S. W.
  • Source: Climatic Change
  • Volume: 99
  • Issue: 1-2
  • Year: 2010
  • Summary: This study investigates the cost of soil carbon sequestration in the Midwest US. The model addresses several missing components in earlier analyses: the link between the residue level choice and carbon payments, crop rotations, carbon loss when shifting from conservation to conventional tillage and the spatial pattern of carbon sequestration across different soil types. The results suggest that for $100 per metric ton of carbon, 1.5 million metric tons of carbon could be sequestered per year on the 19.9 million hectares of cropland in the study region. These estimates suggest less carbon potential than existing studies because the opportunity costs associated with conservation tillage are fairly high. Annual carbon rental payments are found to be more efficient, as expected, but for smaller programs, per hectare rental payments are not substantially more costly.
  • Authors:
    • Sommer, R.
    • Ryan, J.
  • Source: Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world, Brisbane, Australia, 1-6 August 2010. Division Symposium 3.2 Nutrient best management practices
  • Year: 2010
  • Summary: While globally fertilizers have had a major impact on food production for the past half-century, the general use of chemical fertilizers in the semi-arid areas of the world is a more recent development. This is particularly true of the Mediterranean region, especially in North Africa and West Asia. Traditionally, the cropping system involved growing cereals (barley and wheat) in rotation with fallow to conserve moisture; sheep and goats were an integral part of the low-input system. Drought was a constant constraint on crop yields. In the past few decades, significant developments have occurred to increase agricultural output; new high-yielding disease resistant varieties; mechanization; irrigation; pest control; and particularly the use of chemical fertilizers as a supplement to the limited animal manures available. Research at the International Center for Agricultural Research in the Dry Areas (ICARDA) in collaboration with the national agricultural systems in the mandate countries of the region has made significant strides in fertilizer research. While much has been achieved in terms of best fertilizer management practices, much remains to be done. This presentation examines the use of fertilizers under the headings of the best management practice concept; right source, right application rate, right time of application, and right place. As fertilizer use will expand in the Mediterranean region, efficiency of use will be an underlying consideration. As agricultural land is on a global level is finite, with limited possibilities to expand cultivation, the increasing population of the world has correspondingly increased the needs for food and fibre. An inevitable development has been intensification of land use, particularly in developing countries of the world, leading to poverty and increased concerns about food security (Borlaug 2007). Pressure on land has been particularly acute in the arid and semi-arid regions, which are characterized by drought and land degradation. The lands surrounding the Mediterranean have been cultivated for millennia and are the site of settled agriculture and the center of origin of some of the world's major crops, especially cereals and pulses. Much development efforts have centered on the West Asia- North Africa (WANA) area, which is characterized by a Mediterranean climate and where drought is the main production constraint (Smith and Harris 1981).