• Authors:
    • Nacci, S.
    • Ramos, M. C.
    • Pla, I.
  • Source: Soil Science
  • Volume: 165
  • Issue: 5
  • Year: 2000
  • Summary: In the vineyards of the Anoia-Alt Penedes region of NE Spain, erosion problems arising from a combination of soil and climate characteristics and their relief have been accelerated in the last few decades as a consequence of new cropping/planting patterns and soil management practices involving continuous tillage, which leaves the soil bare most of the time. In the rain-fed vineyards of the area, rainfall water conservation in situ has also become a problem that influences the production of high quality wine. The determination of the actual and potential erosion processes required for rational selection, design, and application of soil and water conservation practices requires identification and quantification of the hydrological properties and processes that induce runoff and soil erosion. Laboratory studies in 10 representative surface soils of the region, using simulated rainfall, proved that erosion losses were highly related to the surface sealing susceptibility of the soils, which reduced minimum rainfall water intake rates to 1 to 7 mm h(-1) or less after only 10 minutes of rainfall. This susceptibility was highly correlated with the high silt and low organic matter content of the soils. In most of the soils, surface protection by a cover was found to increase the minimum rainfall water intake rate 50 to 200 times. A simple laboratory test, based on the measurement of saturated hydraulic conductivity and the time to reach its minimum value, measured efficiently the sealing susceptibility of the studied soils and the relative effect of a protective cover. The minimum value of saturated hydraulic conductivity was highly correlated to runoff and soil erosion losses in soil boxes under simulated rainfall.
  • 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:
    • Düring, R. A.
    • Tebrügge, F.
  • Source: Soil & Tillage Research
  • Volume: 53
  • Issue: 1
  • Year: 1999
  • Summary: This paper reviews research performed at the Justus-Liebig-University of Giessen, Germany into the impact of different tillage systems on soil properties and quality. The impact of intensive soil tillage treatments on several soil properties was described by means of selected data obtained through long-term interdisciplinary research. The experiments were based on comparative application (long-term, up to 18 years investigations) of the respective tillage options on different soils (e.g. Eutric Cambisol, Eutric Fluvisol) ranging in texture from sand to a silt loam. These soils are located at five field sites with different crop rotations in the central German state of Hesse. Tillage intensity of the systems was considered to decrease in the following sequence: Conventional plough tillage (CT), reduced tillage (RT), and no-tillage (NT). For elucidating the impact of tillage intensity, the tillage extremes CT and NT were compared. Physical conditions of soil as influenced by the application of RT were considered to be intermediate between CT and NT. In general, bulk density in the upper layer of NT soils was increased, resulting in a decrease in the amount of coarse pores, and a lower saturated hydraulic conductivity when compared with the CT and RT soils. Surface cover by crop residues and higher aggregate stability under NT protected soil fertility by avoiding surface sealing and erosion. Lateral losses of herbicides were also reduced under NT conditions, whereas the susceptibility for preferential vertical transport of herbicides needs further evaluation. Accumulation of organic matter and nutrients near the soil surface under NT and RT were favorable consequences of not inverting the soil and by maintaining a mulch layer on the surface. Those improvements were associated with enhanced biological activities in NT and RT topsoils. Increased earthworm activity in NT treatments was associated with a system of continuous macropores which improved water infiltration rates. Earthworms support decomposition and incorporation of straw. Soils which have not been tilled for many years were more resistant to vehicle passage; consequently, the compaction by traffic was lower. Penetration resistance curves indicate that a uniformly stable structure had developed over the years in NT soils. Overall, the results show that RT and NT were beneficial to the investigated soil properties. If crop rotation, machinery, and plant protection are well adapted for the introduction of conservation tillage, these systems may replace conventional ploughing systems in many cases in German agriculture. (C) 1999 Elsevier Science B.V. All rights reserved.
  • Authors:
    • Siriwardena, G. M.
    • Bradbury, R. B.
    • Wilson, J. D.
    • Krebs, J. R.
  • Source: Nature
  • Volume: 400
  • Year: 1999
  • Authors:
    • Peters, M.
    • House, R.
    • Lewandrowski, J.
    • McDowell, H.
  • Source: Agricultural Outlook
  • Year: 1999
  • Authors:
    • Schlesinger, W. H.
  • Source: Science
  • Volume: 284
  • Issue: 5423
  • Year: 1999
  • Summary: 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. 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. 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.