Peter Weisskopf

Prevention strategies for field traffic-induced subsoil compaction : a review. Part 2. Equipment and field practices

The loads imposed by modern farm machinery have considerable potential to increase subsoil stress. Within the context of economically viable and environmentally sustainable systems, the practices associated with subsoil damage and methods for avoidance are identified. The greatest potential for damage is on fragile, wet or loosened subsoils combined with high wheel or track loads and contact pressures that create noticeable ruts in the topsoil. In-furrow ploughing increases this potential considerably by placing loads on the subsoil. Measures to avoid this potential involve a whole farm approach and an understanding of the many interactions between cropping systems and machinery. Alternatives to in-furrow ploughing that involve working from the surface and building a protective topsoil are discussed. Key measures to reduce the risk to subsoils involve a clear understanding of tyre load and inflation data and simple on-farm methods of achieving this are suggested. Although avoidance has the potential to reduce the risk, confinement of damage to specific strips in the field is seen as a realistic alternative. Controlled traffic operations, together with precision guidance, offer an economic means by which compaction on the cropped area can be avoided. The most effective route to improvement in soil care across the European Union (EU) is an appropriate management structure coupled with a best practice framework.

Subsoil compaction: risk, avoidance, identification and alleviation

This paper aims to provide guidance for field practitioners on the vulnerability of different subsoils to compaction under different field conditions and on the tyre pressures necessary to reduce or avoid damage. It also indicates ways of identifying situations where some compaction alleviation may be necessary to improve subsoil conditions and methods for alleviating subsoil compaction problems, without increasing the risk of more extensive compaction damage in the future.

A novel method for soil quality in life cycle assessment using several soil indicators

Soil quality is recognised as being a key parameter of sustainable agricultural management. Existing methods of life cycle impact assessment (LCIA) do not include any soil quality indicators other than soil organic matter content. This paper rectifies this omission by presenting Swiss Agricultural Life Cycle Assessment for Soil Quality (SALCA-SQ), a LCIA conform method, to assess effects of agricultural management practices on soil quality. SALCA-SQ characterises all major types of impacts of land management practices on the quality of arable soils by means of nine indicators covering soil physical, chemical and biological aspects: rooting depth of soil, macropore volume, aggregate stability, organic carbon content, heavy metal content, organic pollutants, earthworm biomass, microbial biomass and microbial activity. Since these indicators are not measured directly, the impacts of agricultural management activities are assessed via impact class modelling to determine the most probable changes in soil quality indicators as a result of on-farm agricultural practices. To illustrate the application and results of SALCA-SQ, treatment effects of a long-term field trial on soil quality were assessed and compared against measured field data. The data generated by SALCA-SQ revealed the important influence of fertiliser regime on soil quality. Field measurements generally confirmed SALCA-SQ assessments, but small differences between measured data in different treatments could not be predicted. Case studies on theoretical scenarios covering a broad spectrum of site conditions and management practices demonstrated the potential of SALCA-SQ to assess the effects of the major impact classes on the nine soil quality indicators, thus giving a refined picture of the potential effects of a farming system on soil quality. In principle, these results support the assumption that SALCA-SQ has the potential to assess effects of agricultural management practices on soil quality, but validity in a strict scientific sense remains to be substantiated. In addition, SALCA-SQ can be used by agricultural advisory services and farmers to analyse agricultural management effects on soil quality and move soil management in a more sustainable direction.

50 Jahre organische und mineralische Düngung: Humusgehalte, N‐Ausnutzung und N‐Bilanzen

Nach Umbruch einer Naturwiese wurden während 48 Jahren zehn organische und mineralische Düngungsverfahren geprüft. Der Wechsel von der futterbaulichen zur ackerbaulichen Nutzung hatte bei allen Verfahren ein Absinken des Humusgehaltes von 2,3% auf 1,4–2,1% zur Folge. Bei regelmässiger Stallmistdüngung und bei mineralischer Düngung stabilisierte sich der Humusgehalt nach ca. 35 Jahren auf einem neuen Niveau bei etwa 1,4 bis 1,6%. Bei der Düngung mit Klärschlamm oder Torf stellte sich nach 48 Jahren noch kein neues Gleichgewicht ein. Sowohl die ausreichende mineralische wie auch die organische Düngung förderte die Menge und Aktivität der Bodenmikroorganismen. Die pflanzenbauliche Ausnutzung des Stickstoffs (N) von organischen Düngern betrug während der gesamten Versuchsdauer meist nur 10–30%. Die N‐Ausnutzung mineralischer Dünger dagegen stieg von 20–70% auf 50–80%. Dies gibt einen Hinweis auf ein erhöhtes Umweltgefährdungspotential organischer Dünger. Unter Berücksichtigung der abnehmenden Humusgehalte deuten auch die N‐Bilanzen auf eine erhöhte Umweltgefahrdung organischer Düngung.