Keyline ploughing and tunnel erosion

Discussion in 'Put Your Questions to the Experts!' started by Jason_H, Oct 25, 2017.

  1. Jason_H

    Jason_H Member

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    Have heard that in SE and now SW Australia there is a problem with tunnel erosion, with a local consultant saying that keyline ploughing exacerbates this. I was wondering if anyone else had come across this and thoughts about it.

    I'm not convinced due to the profile of disturbance that running a keyline or similar plough produces. But I'm also a novice to this area and keen to learn.
     
  2. Bryant RedHawk

    Bryant RedHawk Junior Member

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    "Tunnel erosion commonly occurs on slopes that have subsoil easily dispersed by water and a surface soil that is much less erodable due to its inherent structure, chemical composition or the presence of plant roots. As the subsoil begins to wash out, tunnels form under the more stable surface soil and extend up the slope, increasing in size after each bout of heavy rain. If the tunnels become large the surface soils may collapse forming a small gully." This is the same occurrence as the formation of a sink hole, and has the possibility of the same injury occurrences to humans and animals.

    If you are properly using Keyline plowing this should not occur because we use this method to get organic matter deeper into the soil profile and we are going to immediately seed the area with deep rooting grasses and other plants. The whole idea of keyline plowing is to get water to sink deeper into compacted soils, and roots are key to the whole idea and purpose of ripping the channels in the first place. Soil horizons are something you should know before you make the decision to keyline plow any space. If you have a #2 horizon that is as hard as concrete, it would be better to plow shallow the first time and let the roots do some of the work for you prior to using the plow at full depth, this would reduce the possibility of tunnel erosion happening.
     
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  3. Jason_H

    Jason_H Member

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    Thanks for the interesting reply. I suppose the best course of action would be to do many soil profile studies on our farm (110 ac) and then work out suitable depths for any keyline ploughing, before planting out deep rooting plants. I was thinking evergreen trees would be good as well as deep rooted pasture species.
     
  4. Bryant RedHawk

    Bryant RedHawk Junior Member

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    Most evergreen trees don't have deep roots, that's why they are usually the first trees to be blown down in high wind storms, they don't have a tap root.
    Oaks, Hickories (including pecan), Walnuts and Locust species are the trees with really deep, strong tap roots.
     
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  5. Jason_H

    Jason_H Member

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    Thanks for the reply again Bryant Redhawk,

    I was told by an experienced local soil scientist who specialises in tunnel erosion, that evergreen trees are preferred because they hydraulically remove water from the soil all year, including the wetter months (which is winter here), which is also when the deciduous trees would be dormant with no sap flow. So from a tunnel erosion perspective, he says evergreen trees would be removing more water during the wetter months compared to deciduous trees, and hence reducing tunnel erosion risk somewhat...

    I agree with you that the actual root structure is important too. It would be preferable that the roots are all the way from the topsoil down and well into the subsoil, bridging the soil layers at risk of tunnel erosion and mechanically holding the soil layers in place.

    Maybe a combination of both (evergreen, deep rooted species) is the absolute best option for a high tunnel erosion risk slope. Something like the local eucalyptus trees would fit that bill. I would prefer less flammable trees though for bushfire risk reduction in summer (dry) months...

    Would appreciate your thoughts if you have the time.

    Jason
     
  6. Bryant RedHawk

    Bryant RedHawk Junior Member

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    If you want the best suck the land dry trees those would be the willows, one willow tree can suck up around 50 gallons of water a week. Since pines don't have a great root structure the willows might be the best choice since they do have deeper roots overall and they sport a tap root.

    When I refer to winter I am referring to the dormant deciduous season, not the months.
    Pines are a lot like eucalyptus trees in a fire situation, the resins are very flammable and pines like to explode when in a very hot fire, They turn into super splinters that spread like shrapnel.
     
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  7. Jason_H

    Jason_H Member

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    Thanks again for the reply. Will have to look further into the best tree species and what we want to do, with respect to keyline and tunnel erosion.
     

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