Thursday, February 25, 2010

Year 8 History, Medieval Crop Rotation

I haven't had much response to last week's request for suggestions on crop rotations except for Laurie who plans to grow his Toms in 500mm pots next season because his soil is infested with either Fusarium or Verticillium.  Follow the link if you want more detail on either of these diseases but for our purposes the symptoms are very similar.  Fusarium is more noticeable in warm conditions, Verticillium when it is cool. Both of these fungi enter the plant through the roots and damage the stem of the plant choking off supply of water and nutrient to the foliage causing wilting and eventually plant death.
Fusarium wilt symptom and a pic showing damage to the plant stem.
Picture from Plant Pathology on line

A common solution, in fact the ancient solution is to rotate crops.  That is, avoid growing Tomatoes (or Potatoes and possibly Capsicum & Chilli as they are all related) in the same soil year after year.  Laurie has been using a 3 year rotation for his Tomatoes but has found that even this is not enough... I still remember 3 field rotation systems from year 8 history.  'Barney' Rundle made a great deal of this fact, I have no idea why.   Any way the crop rotation idea is that the fungal spores will eventually die after a few seasons if they don't find a host plant to grow and reproduce in.  But spores and seeds are fantastic plant survival agents and can survive terrible conditions for remarkable periods, just look at the wild flower shows in Central Australia (I hear the Todd river is in flood so we should see news reports of the "desert in bloom" in the next few weeks).  As we learned from Mr Rundle the three field system, one year with one crop, one year with another and the the third fallow was both inefficient and eventually unsuccessful in controlling disease.

From my reading most vegie gardening books recommend disease resistant cultivars.  This brings us back to the old question of Heirlooms vs. Hybrids.  Laurie's favourite Tomato is a classic Heirloom, Brandywine.  Half Kilo fruit if you believe him, pink skinned and solid fleshed.  Actually Laurie if you're growing fruit like that why change your system?  From my experience disease resistant varieties only offer a limited defense against heavily infested soil.

Brandywine Tomato pick from tradewindsfruit.comFollowing last week's newsletter note the cracking on the shoulder of this fruit.

Now there is one other method for protecting your garden plants from soil borne diseases: Fumigation.  Yes it is as bad as it sounds.  When we cleared out my grandfather David's garage I found a 4' tall cylinder of  Methyl Bromide.  This is filthy stuff that used to be used to kill every living thing in the soil for commercial vegetable and flower growers.  Clearly Dave had brought some home.  Well you know, he loved his flower beds.  Any way I'm sure Methyl Bromide has been banned altogether now.  Interestingly because potting mix can be "picked up" it can be steam pasteurized killing most harmful organisms but leaving the "media" inoculated with helpful bugs.  This is a bit beyond the home gardener.
So back to Laurie's original suggestion. Grow Tomatoes in big pots.  I think it's a great idea but not cheap.  If you use pots you must use good potting mix and Laurie is proposing pots twice as big as Kerry used at home this year so that's a lot of potting mix.  Of course you will remember that Kerry's 250-300mm pots just weren't big enough to supply enough nutrient or water to advanced Tomato plants.  And since we're talking about crop rotations the potting mix needs to be replaced for next year's crop or the benefit will be lost and don't forget that the big pots need to be washed out with disinfectant to ensure that all the fungal spores are gone.

That feels like a lot of reading today, see you next week I've got a great idea about attracting Lady Birds and other insect predators.
Oh and Happy Birthday to Laurie who turns 81 on Wednesday.


  1. I found that a very informative read. I'm quite the novice at growing tomatoes and have some 'Tommy Toes' in pots that were sown a bit late but are now in flower, so hopefully they'll make it in time. I'm now guessing that at least a couple of them are in pots that are too small. Oh wel, I'll see it through for the experiment if nothing else!
    Looking forward to the ladybird post - we didn't have any this year!

  2. Thanks gippygardener. Hope you like green tomato pickles. I do!

  3. help help help
    I really need to know what the medieval crop rotation system is!!!!!!!!!!!!!!!!!!!!!
    Love Anonymous

    Please help me gippy gardener


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