• Authors:
    • Dao, T. H.
    • Douglas, C. L.,Jr.
    • Schomberg, H. H.
    • Allmaras, R. R.
  • Source: Journal of Soil and Water Conservation
  • Volume: 55
  • Issue: 3
  • Year: 2000
  • Summary: Soil organic carbon (SOC) makes up about two-thirds of the C pool in the terrestrial biosphere; annual C deposition and decomposition to release carbon dioxide (CO2) into the atmospheric constitutes about 4% of this SOC pool. Cropland is an important, highly managed component of the biosphere. Among the many managed components of cropland are the production of crop residue, use of tillage systems to control crop residue placement/disturbance, and residue decomposition. An accumulation of SOC is a C sink (a net gain from atmospheric CO2) whereas a net loss of SOC is a C source to atmospheric CO2. A simple three components model was developed to determine whether or not conservation tillage systems were changing cropland from a C source to a C sink. Grain/oil seed yields and harvest indices have indicated a steadily increasing supply of crop residue since 1940, and long term field experiments indicate SOC storage in no-tillage > non moldboard tillage > moldboard tillage systems. According to adoption surveys, moldboard tillage dominated until about 1970, but non moldboard systems are now used nationally on at least 92% of planted wheat, corn, soybean, and sorghum. Consequently, since about 1980, cropland agriculture has become a C sink. Moldboard plow systems had prevented a C sink response to increases in crop residue production that had occurred between 1940 and 1970. The model has not only facilitated a qualitative conclusion about SOC but it has also been used to project production, as well as soil and water conservation benefits, when a C credit or payment to farmers is associated with the C sink in cropland agriculture.
  • Authors:
    • Rhinhart, K.
    • Walenta, D.
    • Harris, G.
    • Patterson, L.
    • Wysocki, D.
    • Ball, D.
    • Smiley, R.
    • Merrifield, K.
  • Source: Biological and Cultural Tests for Control of Plant Diseases
  • Volume: 15
  • Year: 2000
  • Summary: Root lesion nematode numbers in soil and wheat roots were evaluated on the sixth year of a crop rotation and tillage management study in Oregon, USA. Seven treatments were established in 1993 and culminated with all plots planted with winter wheat in 1999. Treatments comprised: (1) two-year rotation of winter wheat and high-residue fallow, using a disc in autumn following harvest and a chisel plough to prepare fallow in spring; (2) two-year rotation of winter wheat and high-residue fallow, using a chemical fallow in autumn following harvest and chisel plough in standing stubble; (3) three-year rotation of winter wheat, spring barley and fallow with tillage as in treatment 1; (4) three-year rotation of winter wheat, spring barley and fallow with chemical fallow as in treatment 2; (5) three-year rotation of rape, winter wheat and fallow with tillage as in treatment 1; (6) two-year rotation of winter wheat and low-residue fallow using a mouldboard plough during spring (current conventional practice with wheat stubble standing through winter following harvest); and (7) continuous no-till spring wheat for five years and winter wheat during 1998-99. Pratylenchus neglectus was the dominant soil lesion nematode and the only species obtained from the roots. P. thornei occurred in soil of some treatments but its ratios were not determined. The highest numbers of lesion nematodes and lowest grain yields occurred in treatments where wheat followed another crop rather than fallow (e.g. annual wheat and the 3-year rotation of rape, winter wheat and fallow). Yield was inversely associated with lesion nematode numbers in roots and soil. There were no relationships among stunt or nonparasitic nematodes and crop history or wheat grain yield.
  • Authors:
    • Pannkuk, C. D.
    • McCool, D. K.
  • Source: 2000 ASAE Annual International Meeting, Technical Papers: Engineering Solutions for a New Century. 
  • Year: 2000
  • Summary: Burn/low-till management of winter wheat is being practiced by some growers in the higher rainfall areas of the Pacific Northwest Wheat Region. The burning eliminates the numerous seedbed tillage operations that are normally required to reduce residues and control weeds and diseases in continuous winter wheat production. Detrimental effects of burn and till systems are well documented. However, there is little or no data on the effects of burning with no or low-till annual cropping on either erosion or soil quality. A three-year field study comparing erosion resulting from burn/low-till (BLT) seeded winter wheat following winter wheat and conventionally managed (CM) winter wheat following various crops was completed in 1997. Results indicate soil loss from the BLT fields was not significantly different from that from the CM fields with various crops preceding winter wheat. For the BLT fields, soil loss was as closely related to soil disturbance (tillage operations) as to surface residue. When residue and crop cover did not differ with the number of tillage operations, an increased number of tillage operations after burning loosened the soil and resulted in greater soil loss. The results of this study indicate no adverse effects on soil loss from using the BLT with one or two-pass seeding of winter wheat following winter wheat.
  • Authors:
    • Tonkin, C. J.
    • Dellow, J. J.
    • Mullen, C. L.
  • Source: Weed control in winter crops 2000 Weed control in winter crops 2000.
  • Year: 2000
  • Summary: This guide provides information on chemical weed control in New South Wales, Australia, for the following winter crops: wheat; barley; oats; rye; triticale; canola [rape]; safflower; lentils; linseed; lupins; chickpeas; faba beans; field pea; and fallows.
  • Authors:
    • Powell, C.
  • Source: New South Wales Department of Agriculture
  • Year: 2000
  • Summary: This report presents tabulated yield data from variety trials held in New South Wales, Australia, for barley, rape, faba beans, field peas, lentils, lupins, mixed cereals (barley, oats, triticale and wheat), oats, triticale, wheat.
  • Authors:
    • Powell, C.
  • Source: New South Wales Department of Agriculture
  • Year: 2000
  • Summary: Tabulated data on yield are presented from variety trials conducted in New South Wales, Australia, during 1999 for barley, rape, chickpeas, faba beans, field peas, lentils, lupins, mixed cereal (barley, oats, rye, triticale and wheat), oats, triticale and wheat.
  • Authors:
    • Soderstrom, M.
    • Rydberg, A.
  • Source: Proceedings of the 5th International Conference on Precision Agriculture, Bloomington, Minnesota, USA, 16-19 July, 2000
  • Year: 2000
  • Summary: This study investigates the potential of using SPOT multispectral images of agricultural fields to distinguish spatial variation in crop-growth patterns that can be used for site-specific agricultural management. Four years of SPOT data from 1995 to 1997 and 1999 are used in this study over south-western Sweden where satellite derived yield maps are compared to data from commercial yield mapping systems. The crops included rape, wheat, barley, meadow fescue [Festuca pratensis], oats, peas and rye. Our concept of crop growth maps is intended for use in areas where yield mapping, soil sampling and ground spectral measurements are not available. Maps of crop growth variability produced by clustering processes applied to images of the Normalized Difference Vegetation Index are compared to clustering of yield maps from the same years. Qualitative yield estimation is derived by dividing each field into several thematic classes, going from lowest to highest potential yield within a particular field. Qualitative comparisons are made within each field. For one year, the satellite data are also compared to three traditional yield maps derived from the same set of yield data. For a few fields where the time of image acquisition coincides with stages of optimum grain fill, high correlations were obtained between yield and NDVI. This study illustrates that satellite images can be a useful tool in precision agriculture management. The clusters created from the NDVI images show similar patterns as clusters created from the yield maps.
  • Authors:
    • Stenberg, B.
    • Stenberg, M.
    • Rydberg, T.
  • Source: Applied Soil Ecology
  • Volume: 14
  • Issue: 2
  • Year: 2000
  • Summary: The effects of reduced tillage and lime on crop yield and soil physical and microbial properties were studied in a weakly-structured silty clay loam soil at a site in Sweden. Two autumn primary tillage practices were compared, mouldboard ploughing to 20-25 cm and cultivation to 12 cm. Seedbed preparation was carried out by several harrowing operations in the mouldboard ploughed treatment, and with a harrow in the same operation as sowing in the shallow cultivation treatment. The tillage treatments were applied alone or were combined with liming aimed at soil structural improvement. Lime was added as 6.5 t CaO ha -1 before the start of the experiment and mixed into the top 12 cm of soil with a disc cultivator. A 4-year crop rotation was used: spring barley, spring oilseed rape, spring/winter wheat and oats, and all crops were compared each year. Crop residues were retained in the experiment and incorporated at cultivation. Aggregate stability was improved by the shallower tillage depth, probably as an effect of an increase in soil organic matter and a more active microbial biomass. Liming had little effect on soil structure variables but increased microbial activity to some extent. This was reflected in higher crop yields, especially when the shallow tillage depth was combined with liming. Penetration resistance in the seedbed subsoil was highest when mouldboard ploughing was carried out in plots without liming. Data were examined with principal component analyses, and the structures in the data were presented as scores and loading plots, which showed groupings between samples and relationships between variables, respectively.
  • Authors:
    • Clark, K.
  • Source: Regional on-farm experiments 1999: Deniliquin, Finley, Hillston, Leeton & Beckom agronomy districts
  • Year: 2000
  • Summary: Tabulated yield data are presented from variety trials conducted throughout New South Wales, Australia, for barley, rape, lentils, lupins, oats, peas, wheat and narbon ( Vicia narbonensis).
  • Authors:
    • Knezevic, S. Z.
    • Leeson, J. Y.
    • Thomas, A. G.
    • Acker, R. C. van
    • Frick, B. L.
  • Source: Canadian Journal of Plant Science
  • Volume: 80
  • Issue: 4
  • Year: 2000
  • Summary: In 1997, a weed survey was conducted during July and August in fields of wheat, barley, oat, canola [rape] and flax in Manitoba, Canada. Field selection was based on a stratified-random sampling methodology using ecodistricts as strata. Species in the Poaceae family were most commonly observed in the survey, followed by species in the Polygonaceae, Asteraceae and Brassicaceae families. The six most abundant weed species were green foxtail ( Setaria viridis), wild oats ( Avena fatua), wild buckwheat ( Polygonum convolvulus) [ Fallopia convolvulus], Canada thistle ( Cirsium arvense), red-root pigweed ( Amaranthus retroflexus) and wild mustard ( Sinapis arvensis). The survey highlighted significant differences between ecoregions and between crops in residual weed infestations. The weed community in the Boreal Transition ecoregion was dominated by seven species, whereas fields in the Aspen Parkland and Lake Manitoba Plain ecoregions were dominated by two species and the Interlake Plain ecoregion was dominated by only one species. Although significant differences were found between the weed communities in crops, they were not as great as differences between ecoregions. The Manitoba residual weed community in 1997 was very similar to that reported for 1978-81 and 1986, suggesting that the same species should remain a focus for weed management.