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Soil structure and turning the soil over


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  • Soil structure and turning the soil over

    I was intrigued to read that ploughing causes the loss of Potassium from the soil - necessitating the use of fertilisers. (Natures Building Blocks - Oxford University Press).

    I then went on to find several references to the destructive properties of ploughing from Wikipedia

    "Problems with mouldboard ploughing
    Mouldboard ploughing has become increasingly recognized as a highly destructive farming practice with the possibility of rapidly depleting soil resources. In the short term, however, it can be successful, hence the reason it was practised for such a long time. A field that is mouldboarded once will generally have an extraordinary one time yield as the larvae of pests and seed from weeds are buried too deeply to survive. After the first harvest, however, continued mouldboarding will diminish yields greatly.

    The diminishing returns of mouldboard ploughing can be attributed to a number of side effects of the practice:-

    Foremost is the formation of hardpan, or the calcification of the sub layer of soil. In some areas, hardpan could once be found so thick it could not be broken up with a pickaxe. The only effective means of removing hardpan is using a "ripper", or chisel plow, which is pulled through the hardpan by an extremely powerful and costly tractor. Obviously, this layer eventually becomes impenetrable to the roots of plants and restricts growth and yields. This layer also becomes impenetrable to water, leading to flooding and the drowning of crops.
    Mouldboard ploughing rapidly depletes the organic matter content of soil and promotes erosion; these two problems go hand in hand. As soil is brought to the surface, the root structure of the previous harvest is broken up, and the natural adhesion of soil particles is also lost; though loose soil appears good for plant germination (and it is), this loose soil without cohesion is highly susceptible to erosion, multiplying the rate of erosion by several factors compared to a non-mouldboarded plot. This increased rate of erosion will not only outpace the rate of soil genesis but also the replacement rate for organics in the soil, thus depleting the soil more rapidly than normal.
    Mouldboard ploughing leads to increased soil compaction and loss of pore space within the soil. Soil is a bit like a bucket full of balls filled with sand. Each ball represents a cohesive particle of soil, and when stacked the balls leave a great deal of air space, required for healthy root growth and proper drainage. Mouldboarding so disturbs the soil that it breaks these balls and releases their contents. When this happens, the much smaller particles that are within the larger particles are released and pore space diminishes, leading to hard compacted soil that floods easily and restricts root growth.

    [edit] Soil erosion
    One negative effect of plowing is to dramatically increase the rate of soil erosion, both by wind and water, where soil is moved elsewhere on land or deposited in bodies of water, such as the oceans. Plowing is thought to be a contributing factor to the Dust Bowl in the US in the 1930s. Alternatives to plowing, such as the no till method, have the potential to limit damage while still allowing farming

    It made me think twice about turf stripping and double digging. In turning a patch of the grass (polytunnel) back into a veg patch I have tried to retain as much of the topsoil as possible. I will however need to add a lot of compost and manure to compensate.

    Should we really be breaking up the soil as much as we are? I have a hand tiller (?) from Lidl which goes down 10cm or so. Is that doing damage to the topsoil by breaking it up too much.

  • #2
    You are missing the point here I think.

    First this refers to Ploughing.
    Second you do not plough, you dig.
    Third other stuff.
    I'll address these in turn.

    Plough scrapes along through the soil at a set depth.
    Repeated ploughing "polishes" the soil "surface" at that depth creating the pan refered to. A Chisel plough is not very good at breaking up the pan as it can also skid along the top of it.

    A "sub-soiler" is more effective tool. From a frame on the back of the tractor hangs a sort of sledge which has a 1/2" by 1' steel plate going down a couple of feet and on the end is fixed a steel plug with a pointed nose and some very strong little stubby wings on each side, angled slightly tail up. When drawn through the ground this tool's wings help push it down to it working depth below the pan where its passage through the soil rips a groove in the pan and heaves big lumps of soil about.

    Badly described, but imagine what water does around a dolphin, then imagine an indestructible dolphin swimming through soil, which cannot flow as easily as water.

    You do not plough.
    You dig, you insert a spade or fork into the ground and randomly fracture a lump from the ground, then turn it over. You are not forcing a heavey iron tool across the ground.
    You normally single dig, reserving double-digging for every third year (for arguments sake taking into account the effort), double digging you go down deeper.
    Double digging you do NOT mix the two levels if you do it right. You dig out a trench, reserve that soil, dig the bottom of the trench, dig a new parralell trench throwing the soil into the previous trench, repeat until finished then throw the reserved soil into the last trench.

    Other Stuff.
    This is why you are adding compost, soil conditioners, farmyard manure, stale manure, etc when you double dig. Do add it when you single dig if you have enough. Most important is to fork manure into the bottom of the trench when double digging.

    Ploughing is done by farmers with big machines in big fields to prepare the field the most cost effective way for next crop. The bigger the field, the easier it is, so few hedges or shelter from wind. The more of a field you cultivate the more you can grow, so no headland left or as one local farm does, back the tractor up to the riverbank with the plough over the river, lower and start ploughing in thin air. Guess where the rainwater runs to and guess what it pulls with it.

    Digging is done by people in gardens to make the soil more productive, remove weed roots and prepare for the next crop. It is done in small areas, a ten rod allotment looks big when you start to dig it, imaginf a tractor parked on it. They tend to be better sheltered than fields.

    Extreme analogy, ploughing is like putting polyfilla on the wall, digging is like chiselling the wall.

    Reference The Great Dustbowl in USA 1930s(?) intensive agricultural ploughing, removal of larger plants (trees, woods, hedges) and no organic (manure) input, combined with a drought to produce an enivornmental and human disaster where fields blew away in the wind.

    Hope this helps.
    Always thank people who have helped you immediately, as they may not be around to thank later.
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    • #3
      Agree with Peter. On our allotments and in our gardens we don't plough. Some digging is necessary, especially when taking over a new plot - it's the only way to remove perennial weeds, for instance, especially if you're against using chemical weedkillers. Also if the soil is really hard packed you do need to loosen it initially so that your plants can get their roots down into it. After this initial digging and clearing you can, if you wish, use a no-dig system of beds - just clearing weeds as they occur and adding compost on top of the existing soil.


      • #4
        I don't dig: have not done for 20 years in same garden.. Lots of compost and scratch the surface with a hoe...

        Digging is BAD for gardeners.


        • #5
          I have single dug my two overgrown allotments and taken out as many weeds as I could. It has taken me four months of nights and weekends!

          I won't be doing it again....ever,ever ever. The beds are covered with a thick mulch of well rotted moisture retaining manure. The main problem I am still having, is thistles which are slowly diminishing as I do my rounds each day pulling them out and laying them on top of the mulch to be frizzled by the sun (when it shines!)

          To me this is a natural process, the surface is full of soil acting fauna pulling the mulch into the soil, enrichening it, giving it better water retention and improving the soil structure in the area the crops are rooting into!

          An annual mulch of manure and a hoe and rake for the seedbeds is the only soil work I should need to do.
          Why do I need to dig? when I've got loads of little wriggly unpaid workers to do it for me!
          My Majesty made for him a garden anew in order
          to present to him vegetables and all beautiful flowers.- Offerings of Thutmose III to Amon-Ra (1500 BCE)

          Diversify & prosper


          • #6
            I did double digging putting the turf two spades depth down last year in 10% of the polytunnel - it was real grief!

            This year I am stripping the turf, removing as much of the soil as possible from the turfs then didding the soil over. Once I have removed the stones (fork) I am using the Lidl rotavator. This breaks up the bigger lumps nicely.

            I do worry that I am losing the most fertile couple of inches but with buttercups, daisies and grass see little alternative.


            • #7
              You can stack the turf - green side down! for a couple of years. You then get a lovely crumbly loam.
              Whoever plants a garden believes in the future.

     Updated March 9th - Spring


              • #8
                Originally posted by Flummery View Post
                You can stack the turf - green side down! for a couple of years. You then get a lovely crumbly loam.
                Or you can use it as it is, upside down to grow melons in the greenhouse!
                My Majesty made for him a garden anew in order
                to present to him vegetables and all beautiful flowers.- Offerings of Thutmose III to Amon-Ra (1500 BCE)

                Diversify & prosper


                • #9
                  I removed the turf and dug as far down as I could in my compacted and VERY stony soil then added a load of new topsoil as well as soil improver. Won't the new topsoil give back the nutrients I have removed? I was planning on just turning over the top again next year and adding more manure, and feeding the crops as they grow - not having a clue what I'm doing, now I'm not sure this is the best plan? This digging lark seems to be more complicated than it first appears!
                  Life may not be the party we hoped for but since we're here we might as well dance


                  • #10
                    what good does it do to put lime on the allotment


                    • #11
                      Originally posted by mint View Post
                      what good does it do to put lime on the allotment
                      You only need lime the area you intend growing brassicas in! Lime makes the land more alkaline and brassicas prefer a higher PH than other veg. It also helps ward off clubroot which prefers an acid soil.
                      I believe lime has a number of other uses, ie sweetens the soil, slugs don't like it and I think it is tied in with flocculation which helps break up clay soils?
                      Last edited by Snadger; 13-09-2007, 03:47 PM.
                      My Majesty made for him a garden anew in order
                      to present to him vegetables and all beautiful flowers.- Offerings of Thutmose III to Amon-Ra (1500 BCE)

                      Diversify & prosper


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