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  • CSIRO Publishing  (3)
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  • CSIRO Publishing  (3)
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  • 1
    Online Resource
    Online Resource
    Upper subsoil pore characteristics and functions as affected by field traffic and freeze–thaw and dry–wet treatments
    CSIRO Publishing ; 2017
    In:  Soil Research Vol. 55, No. 3 ( 2017), p. 234-
    Details
    In: Soil Research, CSIRO Publishing, Vol. 55, No. 3 ( 2017), p. 234-
    Abstract: Cultivated soils are subject to very high stresses from machinery. This may affect the soil pore system and its processes, soil functions and soil ecosystem services. Compaction experiments were performed on loamy Luvisols at three sites in Denmark: Aarslev, Flakkebjerg and Taastrup. Non-trafficked control soil was compared with soil subjected to four annual traffic events with approximately 3-, 6- or 8-Mg wheel loads from tractor–trailer combinations. A self-propelled machine with a single pass of approximately 12-Mg wheel load was tested at Aarslev. Undisturbed soil cores were sampled at 0.3m depth when the experimental plots had received either 2 years (Flakkebjerg) or 3 years (Aarslev and Taastrup) of repeated compaction treatment. The volume of air-filled pores and air permeability were quantified for soil drained to –100hPa matric potential. Freeze–thaw and dry–wet treatments were applied to soil cores in the laboratory for Aarslev and Taastrup samples. The multipass machinery significantly affected 〉 30µm soil pores and air permeability at wheel loads of ~6 Mg or higher, whereas no or only minor effects could be detected for ~3-Mg wheel loads. Indices combining air permeabilities with air-filled porosities indicated that pore morphological features had also been affected. Estimates of hydraulic conductivity indicated critical conditions for the percolation of excess rainwater for severely compacted soil at Aarslev. Generally, the single-pass machine with a high wheel load did not affect the pores and their function. A dry–wet event was a more effective remediation of compaction than a freeze–thaw treatment. In conclusion, present-day field traffic risks creating a bottleneck soil layer for important soil functions just below the tilled topsoil.
    Type of Medium: Online Resource
    ISSN: 1838-675X
    URL: Article
    DOI: 10.1071/SR16149
    Language: English
    Publisher: CSIRO Publishing
    Publication Date: 2017
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  • 2
    Online Resource
    Online Resource
    Suboptimal fertilisation compromises soil physical properties of a hard-setting sandy loam
    CSIRO Publishing ; 2017
    In:  Soil Research Vol. 55, No. 4 ( 2017), p. 332-
    Details
    In: Soil Research, CSIRO Publishing, Vol. 55, No. 4 ( 2017), p. 332-
    Abstract: Nutrient management affects not only crop productivity and environmental quality, but also soil physical properties related to soil tilth. Previous studies on soil physical properties have focussed on effects of fertiliser type, whereas the effect of fertiliser rate has been neglected. We examined the impact of no fertilisation (UNF) and different rates of mineral fertiliser (½NPK and 1NPK) and animal manure (1½AM) on an ensemble of soil physical characteristics, with the amount of fertiliser added at level 1 corresponding to the standard rate of plant nutrients for a given crop. Soil was from the Askov long-term field experiment, initiated in 1894 on a hard-setting sandy loam. We assessed clay dispersibility, wet-stability of aggregates, aggregate strength, bulk soil strength and soil pore characteristics. The soils receiving 1NPK and 1½AM had similar soil physical properties, the only differences being a wider range in the optimum water content for tillage and more plant-available water in the soil amended with 1½AM. Suboptimal fertiliser rates (UNF and ½NPK) increased clay dispersibility, soil cohesion and bulk density, and reduced aggregate stability. The physical properties of soils exposed to suboptimal fertilisation indicate that the level of soil organic matter, including active organic binding and bonding materials, has become critically low due to reduced inputs of crop residues. While long-term suboptimal fertilisation compromises soil physical properties, crop-yield-optimised rates of mineral fertilisers and animal manure appear to sustain several soil physical properties equally well.
    Type of Medium: Online Resource
    ISSN: 1838-675X
    URL: Article
    DOI: 10.1071/SR16218
    Language: English
    Publisher: CSIRO Publishing
    Publication Date: 2017
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  • 3
    Online Resource
    Online Resource
    Soil mechanical stresses in high wheel load agricultural field traffic: a case study
    CSIRO Publishing ; 2018
    In:  Soil Research Vol. 56, No. 2 ( 2018), p. 129-
    Details
    In: Soil Research, CSIRO Publishing, Vol. 56, No. 2 ( 2018), p. 129-
    Abstract: Subsoil compaction is a serious long-term threat to soil functions. Only a few studies have quantified the mechanical stresses reaching deep subsoil layers for modern high wheel load machinery. In the present study we measured the vertical stresses in the tyre–soil contact area and at 0.3, 0.6 and 0.9 m depths of a sandy loam soil at field capacity water content. The soil was ploughed annually to a depth of 0.25 m and was tested in the spring following autumn ploughing but before secondary tillage. The machinery tested was a tractor–trailer system for slurry application with a total weight of 52 Mg. Wheel loads ranged from approximately 20 to 70 kN. The tyres were all radial ply with volumes ranging from 0.63 to 1.23 m3. The tyre inflation pressures were generally above those recommended by the manufacturer and ranged from 170 to 280 kPa. The stress distributions in the contact area were highly skewed. Across tyres, the maximum stress in the contact area correlated linearly with, but was much higher than, the mean ground pressure. For each of the three soil depths, the maximum stresses under the tyres were significantly correlated with the wheel load, but not with other loading characteristics. The data predict a 6.6-kPa increase in vertical stress at 0.9 m depth for each 1-Mg addition to the wheel load. The soil stress observations support a simple rule of thumb combining wheel load and inflation pressure in calculation of subsoil vertical stress. We measured vertical stresses up to 300, 100 and 45 kPa at soil depths of 0.3, 0.6 and 0.9 m respectively. Comparing these with the data in the literature regarding soil strength and measured compaction effects on the soil studied, we conclude that the traffic event investigated is likely to induce serious effects on soil properties and functions to a depth of at least 0.7 m.
    Type of Medium: Online Resource
    ISSN: 1838-675X
    URL: Article
    DOI: 10.1071/SR17117
    Language: English
    Publisher: CSIRO Publishing
    Publication Date: 2018
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