• Authors:
    • Hill, J. E.
    • Scow, K. M.
    • Fitzgerald, G. J.
  • Source: Global Biogeochemical Cycles
  • Volume: 14
  • Issue: 3
  • Year: 2000
  • Summary: In response to legislative mandate to reduce postharvest straw burning and environmental concerns to restore wetland habitat for Pacific fly-way waterfowl, California rice growers are incorporating straw into soil and flooding rice fields in winter. These changes were hypothesized to alter soil carbon cycling pathways across the region. The principal objective of this study was to determine how various winter fallowed straw and water management changes would affect year-round methane emissions. Main plots were winter flood and nonflood, and subplots had straw treatments: burned, soil incorporated, or rolled (partially soil incorporated). Results showed the principal factor controlling methane emissions was the interaction of flooding and straw amendments. The presence of either water or straw alone led to low emissions. Winter emissions accounted for 50% of annual totals in straw-amended treatments despite lower temperatures and the presence of plants in summer. Summer emissions were significantly influenced by winter straw amendments but not by winter flood. Postdrain peaks after winter drain accounted for 10-13% of annual emissions in treatments with amended straw. Although rolled and incorporated treatments had similar straw inputs, methane fluxes from rolled treatments were higher than from incorporated treatments. Measurements of methane should be conducted year-round to capture fallow and postdrain fluxes and improve global emission estimates. Regional emission estimates showed that 2.6 times more methane was emitted after flooding plus incorporation was implemented than before the legislative mandate was enacted.
  • Authors:
    • Wilkinson, S. R.
    • Schomberg, H. H.
    • Stuedemann, J. A.
    • Franzluebbers, A. J.
  • Source: Soil Biology and Biochemistry
  • Volume: 32
  • Issue: 4
  • Year: 2000
  • Summary: Soil organic matter pools under contrasting long-term management systems provide insight into potentials for sequestering oil C, sustaining soil fertility and functioning of the soil±atmospheric interface. We compared soil C and N pools (total, articulate and microbial) under pastures (1) varying due to harvest technique (grazing or haying), species composition (cool- or arm-season), stand age and previous land use and (2) in comparison with other land uses. Grazed tall fescue-common ermudagrass pasture (20 yr old) had greater soil organic C (31%), total N (34%), particulate organic C (66%), articulate organic N (2.4 fold) and soil microbial biomass C (28%) at a depth of 0±200 mm than adjacent land in conservation-tillage cropland (24 yr old). Soil organic C and total N at a depth of 0±200 mm averaged 3800 and 294 g m-2 , respectively, under grazed bermudagrass and 3112 and 219 g m-2, respectively, under hayed bermudagrass. A chronosequence of grazed tall fescue suggested soil organic N sequestration rates of 7.3, 4.4 and 0.6 g m-2 yr-1 to a depth of 200 mm during 0±10, 10±30 and 30±50 yr, respectively. Soil C storage under long-term grazed tall fescue was 85 to 88% of that under forest, whereas soil N storage was 77 to 90% greater under grazed tall fescue than under forest. Properly grazed pastures in the Southern Piedmont USA have great potential to restore natural soil fertility, sequester soil organic C and N and increase soil biological activity.
  • Authors:
    • Stuedemann, J. A.
    • Wright, S. F.
    • Franzluebbers, A. J.
  • Source: Soil Science Society of America Journal
  • Volume: 64
  • Issue: 3
  • Year: 2000
  • Authors:
    • Siriwardena, G. M.
    • Chamberlain, D. E.
  • Source: Environmental Reviews
  • Volume: 8
  • Issue: 2
  • Year: 2000
  • Summary: Declines in a number of farmland bird species in northern Europe have been linked to agricultural intensification. In this paper, we review the evidence for the effects of agricultural intensification on farmland bird populations using monitoring studies on a single well-studied species, the Eurasian Skylark (Alauda arvensis). Between 1970 and 1998, the Skylark population declined by 44% and this decline was greatest on farmland compared to upland or coastal habitats, yet during that time, reproductive performance per individual nesting attempt improved significantly. Skylarks consistently prefer relatively sparse (spring cereals) or structurally complex (fallow "set-aside"') crops, particularly late in the breeding season when crops that are too tall or dense are abandoned. Outside the breeding season, cereal stubble is the most preferred foraging habitat. Intensification has been characterized by decreases in preferred crops (spring cereals and cereal stubble) and an increase in unfavourable habitats (winter cereals, oilseed rape, and intensively managed or grazed grass). Reduction in the number of breeding attempts due to rapid sward development of winter cereals and the lack of suitable alternative habitats is likely to have been an important factor in the Skylark decline. The decline may also have been driven by decreases in survival outside the breeding season. Management regimes that include spring cereals, cereal stubble, and low-intensity grazing are likely to increase Skylark abundance and will benefit a number of other farmland birds. This review highlights the great value of large-scale monitoring schemes in understanding population declines. However, the factors affecting the post-fledging survival of Skylarks and the effects of crop diversity on Skylark abundance remain to be resolved.
  • Authors:
    • Adkins, W.
    • West, L. T.
    • Kissel, D. E.
    • Chen, F.
  • Source: Soil Science Society of America Journal
  • Volume: 64
  • Issue: 2
  • Year: 2000
  • Summary: The surface soil organic C (SOC) concentration is a useful soil property to map soils, interpret soil properties, and guide fertilizer and agricultural chemical applications. The objective of this study was to determine whether surface SOC concentrations could be predicted from remotely sensed imagery (an aerial photograph of bare surface soil) of a 115-ha field located in Crisp County, Georgia. The surface SOC concentrations were determined for soil samples taken at 28 field locations. The statistical relationship between surface SOC concentrations and image intensity values in the red, green, and blue bands was fit to a to a logarithm linear equation (R2 = 0.93). The distribution of the surface SOC concentrations was predicted with two approaches. The first approach was to apply the relationship to individual pixels and then determine the distribution; the second approach was to classify the image and then apply the relationship to determine the class boundaries and means. Eight levels of surface SOC concentrations were classified in both approaches, and there was good agreement between the two approaches with a probability value near one using a paired t-test. The predicted and measured surface SOC concentrations, based on additional soil samples from 31 field locations, were compared using linear regression (r 2 = 0.97 and r 2=0.98 for the two approaches). The surface SOC concentrations were correctly classified in 77.4 and 74.2% of cases for the two approaches. The procedures tested were accurate enough to be used for precision farming applications in agricultural fields.
  • Authors:
    • Fernandes, S. V.
    • Martin-Neto, L.
    • Amado, T. J. C.
    • Mielniczuk, J.
    • Bayer, C.
  • Source: Soil & Tillage Research
  • Volume: 54
  • Issue: 1-2
  • Year: 2000
  • Summary: Soil organic matter decline and associated degradation of soil and environmental conditions under conventional tillage in tropical and subtropical regions underline the need to develop sustainable soil management systems. This study aimed first to evaluate the long-term effect (9 years) of two soil-tillage systems (conventional tillage: CT, and no-tillage: NT) and two cropping systems (oat (Avena strigosa Schreb)/maize (Zea mays L.): O/M; and oat+common vetch (Vicia sativa L.)/ maize+cowpea (Vigna unguiculata (L.) Walp): O+V/M+C without N fertilization on total organic carbon (TOC) and total nitrogen (TN) concentrations in a sandy clay loam Acrisol in southern Brazil. The second objective was to assess soil potential for acting as an atmospheric CO2 sink. Under NT an increase of soil TOC and TN concentrations occurred, in both cropping systems, when compared with CT. However, this increase was restricted to soil surface layers and it was higher for O+V/M+C than for O/M, The O+V/M+C under NT, which probably results in the lowest soil organic matter losses (due to erosion and oxidation) and highest addition of crop residues, had 12 Mg ha(-1) more TOC and 0.9 Mg ha(-1) more TN in the 0-30.0 cm depth soil layer, compared with O/M under CT which exhibits highest soil organic matter losses and lowest crop residue additions to the soil. These increments represent TOC and TN accumulation rates of 1.33 and 0.10 Mg ha(-1) per year, respectively. Compared with CT and O/M, this TOC increase under NT and O+V/M+C means a net carbon dioxide removal of about 44 Mg ha(-1) from the atmosphere in 9 years. NT can therefore be considered, as it is in temperate climates, an important management strategy for increasing soil organic matter. In the tropicals and subtropicals, where climatic conditions cause intense biological activity, in order to maintain or increase soil organic matter, improve soil quality and contribute to mitigation of CO2 emissions, NT should be associated with cropping systems resulting in high annual crop residue additions to soil surface. (C) 2000 Elsevier Science B.V. All rights reserved.
  • Authors:
    • Lang, B.
  • Source: Report on farming in the eastern counties of England 1998/99.
  • Year: 2000
  • Summary: The report is divided into two sections. Part I analyses physical and financial data collected from 381 farms in the eastern counties of England (Bedfordshire, Cambridgeshire, Essex, Hertfordshire, South Lincolnshire, Norfolk and Suffolk) for the harvest year 1998. Performance is analysed by district, farm size group and type (mainly cereals, mixed cropping, dairy with arable, pigs and poultry, mixed farms and fen arable). A review of the farming environment in 1998/99 is also included. Part II looks ahead to future policy developments which may result from both internal and external forces. Internal forces include the England Rural Development plan whilst external pressures will arise from World Trade Organization discussions. Key findings are: (i) the lowest farm incomes (for ten years) were recorded on combinable crop and livestock farms; (ii) returns on pig farms declined further; (iii) low prices prevailed for commodity cereals, combinable break crops, milk and all meat; (iv) sterling strengthened against European currencies; (v) exceptional potato prices were available in 1998 restoring fortunes of Fen Arable and Mixed Cropping farms; and (vi) borrowing was inexpensive in a year when indebtedness by farm business increased.
  • 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:
    • 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.