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Tillage

Discover different tillage options, the pros and cons and the effects of tillage on carbon sequestration

Image source: NIAB

Tillage options

A wide range of equipment has been developed for soil cultivation and crop establishment, to meet differing soil, crop, and climate requirements. In the UK however, this can broadly be grouped under four tillage systems, based on the primary cultivation

  • Conventional ploughed

  • Deep non-inversion (typically 20-25cm depth)

  • Shallow non-inversion (typically 10cm or less depth)

  • Zero tillage or direct-drill

 

Conventional ploughing normally requires at least one further cultivation pass to create a seedbed. Non-inversion systems can be just a single pass, based on tines, discs, or a combination, with differing intensities of soil disturbance. These are sometimes referred to as conservation or reduced tillage systems, but some non-inversion systems can be intensive especially where more than one pass is involved.

On appropriate soil types, non-inversion tillage systems and especially zero tillage offer the opportunity to conserve moisture, reduce soil erosion, improve timeliness of cultivations through faster work rates, and/or reduce fuel use. Nevertheless, intensive deep non-inversion systems may take as long, and use as much or more fuel, as conventional plough systems.

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Pros and cons of Tillage options

The most appropriate tillage system for a given situation will depend on several factors, including:

Soil texture

Soil texture: self-structuring clays soils can be well suited to non-inversion or direct drill systems that avoid creating dry, cloddy seedbeds. Whereas unstructured light sandy or fine silt soils may pack too tightly in the absence of significant soil disturbance, leading to poor movement of air and water.

Crop residues

Unlike ploughing, where the aim is to fully incorporate crop residues, non-inversion tillage will typically leave a proportion on the soil surface, whilst all crop residues usually remain on the surface with zero-tillage.

Weed control

Where herbicide programmes and other management practices are failing to adequately control populations of grass weeds, such as black-grass, continuous non-inversion or zero tillage may not be sustainable, with a requirement for ploughing on a rotational basis or in years of high grass weed seed return.     

Effect of tillage systems on carbon capture

The loss of organic matter (and its associated carbon) from agricultural soils has often been attributed in part to tillage. One of the advantages often claimed for reduced intensity tillage is that soil organic carbon (SOC) is maintained at a higher level than with plough-based tillage. Studies over many years have come to differing conclusions as to the impact of tillage on SOC, with some showing a benefit to reduced tillage, and some no effect of tillage system.

A comprehensive review, published in 2017, of 351 studies in temperate regions indicated that zero tillage resulted in a higher SOC concentration in the top 15cm of soil than intermediate intensity tillage, and both were higher than high intensity tillage. But at lower depths (15-30cm), the only difference was between intermediate and high intensity tillage, with the former having a lower SOC concentration. Zero tillage had higher SOC stocks down to 30cm than intermediate or high intensity tillage, but there was no effect of tillage intensity over the full soil profile.

A previous study published in 2007 observed that where soils were sampled to a depth of 30cm or less, conservation tillage resulted in higher SOC than conventional ploughing. But where soils were sampled to below 30cm depth, there was no consistent increase in SOC, just a change in distribution with a higher concentration near the surface under conservation tillage, and a higher concentration in deeper layers under conventional tillage.

Even though reduced tillage may not increase overall carbon capture in the soil, higher SOC stocks or concentrations in the upper soil support a more productive soil with higher biological activity and increase resilience to extreme weather conditions. The reduction in the amount of fuel used for cultivation and establishment will itself also lead to a reduction in carbon dioxide emissions.

More information

  • Brown, J., Stobart, R., Hallett, P. et al. Variable impacts of reduced and zero tillage on soil carbon storage across 4–10 years of UK field experiments. J Soils Sediments 21, 890–904 (2021).https://doi.org/10.1007/s11368-020-02799-6

  • Denis Topa, Irina Gabriela Cara, Gerard Jităreanu. Long term impact of different tillage systems on carbon pools and stocks, soil bulk density, aggregation and nutrients: A field meta-analysis. CATENA, Volume 199, 2021, 105102. ISSN 0341-8162.https://doi.org/10.1016/j.catena.2020.105102

  • Fornara, D., Higgins, A. Tillage and reseeding effects on soil carbon stocks: evidence from 500 agricultural grasslands in the UK. Agron. Sustain. Dev. 42, 71 (2022). https://doi.org/10.1007/s13593-022-00804-5

  • H V Cooper, S Sjögersten, R M Lark and S J Mooney. 2021. To till or not to till in a temperate ecosystem? Implications for climate change mitigation. Environ. Res. Lett. 16 054022https://DOI.org/10.1088/1748-9326/abe74e

  • Haddaway, N.R., Hedlund, K., Jackson, L.E. et al. How does tillage intensity affect soil organic carbon? A systematic review. Environ Evid 6, 30 (2017). https://doi.org/10.1186/s13750-017-0108-9

  • John M. Baker, Tyson E. Ochsner, Rodney T. Venterea, Timothy J. Griffis. Tillage and soil carbon sequestration—What do we really know? Agriculture, Ecosystems & Environment,

  • Volume 118, Issues 1–4, 2007, Pages 1-5. ISSN 0167-8809.https://doi.org/10.1016/j.agee.2006.05.014

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