• Authors:
    • Mielniczuk, J.
    • Martin-Neto, L.
    • Bayer, C.
    • Ceretta, C. A.
  • Source: Soil & Tillage Research
  • Volume: 53
  • Issue: 2
  • Year: 2000
  • Summary: In weathered tropical and subtropical soils organic matter is crucial for soil productivity and its quantity depends heavily on soil management systems. This study evaluated the effect of no-till cropping systems on organic matter content and quality in a sandy clay loam Acrisol soil (Paleudult in US taxonomy) from Southern Brazil. Ten cropping systems with varying additions of C and N were conducted for 12 years (from 1983 to 1994), The addition of crop residues increased total organic carbon (TOC) and total nitrogen (TN) in the soil at 0-17.5 cm depth, and this increase was directly related with C and N added or recycled by the systems. The crop residues added to the soil were associated with reduced semiquinone free radical concentration, detected by electron spin resonance (ESR), in the organo-mineral aggregates <53 mu m and humic acid (HA) samples, in the soil at 0-2.5 cm depth. This showed that stable organic matter originating from crop residues was less humidified than the original soil organic matter. Results obtained from organo-mineral aggregates showed a higher amplitude (highest and lowest values were 5.47 and 2.09 x 10(17) spins g(-1) of TOC, respectively) of semiquinone free radical concentration than HA samples (highest and lowest values were 2.68 and 1.77 x 10(17) spins g(-1) of HA, respectively). These data showed that alterations due to tillage in soil organic matter characteristics, e.g,, humification degree can be better identified through a combination of soil physical fractionation and spectroscopic analysis. Semiquinone content in the HA samples, detected by ESR, related significantly to aromaticity, as measured by nuclear magnetic resonance (NMR) of C-13. Management systems including no-till and cropping systems with high C and N additions to the soil improved its quality in Southern Brazil. (C) 2000 Elsevier Science B,V. All rights reserved.
  • 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:
    • 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:
    • Ulbrich, A. V.
    • Yada, I. F. U.
    • Lima, J. de
    • Rodrigues, B. N.
    • Fornarolli, D. A.
  • Source: Planta Daninha
  • Volume: 18
  • Issue: 2
  • Year: 2000
  • Summary: Field experiments, conducted during 1997/98 in Londrina, Parana, Brazil, bioassays and chromatographic analyses were conducted to investigate the effect of mulch (oat residues) on crop-weed competition and retention of imazaquin in no-till soyabean crop. Imazaquin was applied at 0, 75, 150 and 300 g/ha on 7000 and 14 000 kg/ha of oat residues and on soil without mulch. Twenty-four hours after imazaquin application, the field was irrigated and more samples were collected for bioassays and chromatographic analyses. The weed population consisted of Brachiaria plantaginea, Euphorbia heterophylla and Bidens pilosa. Oat residues intercepted 90% of the imazaquin before irrigation, indicating the potential of this herbicide in no-till system.
  • Authors:
    • Nakarmi, G.
    • Schreier, H. E.
    • Shah, P. B.
  • Source: The people and resource dynamics project: the first three years (1996-1999). Proceedings of a Workshop held in Baoshan, Yunnan Province, China, March 2-5, 1999
  • Year: 2000
  • Summary: Degraded sites are difficult to rehabilitate because of their adverse chemical and physical condition and the large inputs required to restore the physical properties and the soil nutrient pool. Experiments conducted in the Jhikhu Khola watershed showed that fodder trees could be successfully established in hedgerows on degraded non-red soils on quartzite, but that this was a significant challenge on degraded red soils (on phyllite), and extremely difficult on non-red soils on saprolite. Selected groundcover and grasses were established on red soils and the effect of adding various combinations of lime and manure tested. Lemon grass in particular was found to be a successful coloniser on these highly acid soils. Rehabilitation of the nutrient pool with litter additions alone was found to be very slow, but significant improvements were achieved in the carbon pool and soil structure following a two-year period of continuous addition of litter (once every six months). The incorporation of locally grown thetonia species improved the carbon content and soil structure, but had little affect on the soil pH or availability of phosphorus. It seems that addition of litter and lime is the best treatment to overcome the adverse chemical conditions of red soils.
  • Authors:
    • Singh, B. P.
    • Rahman, S.
    • Reddy, V. R.
    • Sainju, U. M.
  • Source: Journal of Environmental Quality
  • Volume: 28
  • Issue: 6
  • Year: 1999
  • Summary: Management practices can influence NO3-N content and movement in the soil. We examined the influence of 3 yr of tillage [no-till (NT), chisel (CH), and moldboard (MB)], cover crop [hairy vetch (Vicia villosa Roth) (HV), and no hairy vetch (NHV)], and N fertilization (0, 90, and 180 kg N ha(-1)) on residual NO3-N content and movement on a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill) in central Georgia. Because of low N recovery by tomato, NO3-N content in the soil increased with depth, regardless of treatments, and ranged from 127 to 316 kg ha(-1) at 0- to 120-cm depth in the fall (September 1997). The content increased with increasing rate of N addition from cover crop residue and N fertilizer. From fall to spring (March 1998), 22 to 58% (37 to 129 kg NO3-N ha(-1)) of this content was lost, mostly due to leaching. Greater loss occurred in NT than in CH or MB, with HV than with NHV, and with 180 or 90 than with 0 kg N ha(-1). Similarly, greater loss at 0- to 60-cm than at 60- to 120-cm depth and significant correlation between soil NO3-N and clay concentration with depth indicates that NO3-N moved from the surface layer to the underlying clay layer, where it moved slowly. Nitrate-N content and movement in the soil from cover crop residue and N fertilizer were similar. Minimum tillage reduced NO3-N movement compared with NT, yet avoided the negative effects on soil and water quality associated with MB. Although HV increased tomato N uptake and recovery, it was not effective in reducing NO3-N content and movement com pared with N fertilizer.
  • Authors:
    • Ray, D. E.
    • Slinsky, S. E.
    • Graham, R. L.
    • Becker, D. A.
    • de la Torre Ugarte, D.
    • Turhollow, A.
    • Perlack, R. L.
    • Walsh, M. E.
  • Year: 1999
  • Authors:
    • Schlesinger, W. H.
  • Source: Science
  • Volume: 284
  • Issue: 5423
  • Year: 1999
  • Summary: first paragraph, "Maintaining and increasing soil organic matter (SOM) adds to soil fertility, water retention, and crop production. Recently, many soil scientists have suggested that the sequestration of atmospheric carbon dioxide in SOM could also contribute significantly to attempts to adhere to the Kyoto Protocol. Conversion of large areas of cropland to conservation tillage, including no-till practices, during the next 30 years could sequester all the CO2 emitted from agricultural activities and up to 1% of today's fossil fuel emissions in the United States (1). Similarly, alternative management of agricultural soils in Europe could potentially provide a sink for about 0.8% of the world's current CO2 release from fossil fuel combustion (2). Beyond conservation tillage, however, many of the techniques recommended to increase carbon sequestration in soils contain hidden carbon "costs" in terms of greater emissions of CO2 into the atmosphere."
  • Authors:
    • Peters, M.
    • House, R.
    • Lewandrowski, J.
    • McDowell, H.
  • Source: Agricultural Outlook
  • Year: 1999