[Fleecewife]

My polytunnel has been under constant cultivation for the best part of 20 years.  In the early days it produced bumper crops and was so prolific it was like a jungle inside.  For the past few years it's gradually been getting less productive, in spite of using the same methods and plenty of compost and manure, and rotating as much as one can in such a small space - 7m x 14m. The plants just don't look totally healthy.  We have had spider mites for the past 3 years.  This year, after having to dispose of the cucumber plants, we have managed to keep the mites at bay by daily soapy spray.  Even so, the sweetcorn is a disaster, yellowed and not well pollinated, and the tomato plants and squashes are decidedly scrawny. We do have gigantic self-sown brassicas though, so it's not all gloom.

Is this soil sickness?  If so, is the only action to move the tunnel to a new location?  What actually causes the sickness?  Is it a build-up of low grade pests and diseases in the soil, or could it be having the soil not rained on for so many years?  When we changed the cover a few years back we left it off for a month to give the rain a chance to soak the soil - there wasn't a single drop of rain in the whole of that month 

If anyone has experience of this phenomenon your experiences and any advice will be gladly received 

[Lesley Silvester]

Have you tried double digging the soil? Alternatively, remove a good layer of soil - at least a spade's depth and replacing it with soil from elsewhere.

[pgkevet]

I'd have thought that significant soil parasites would be noticed. At a guess I'd suggest a trace element imbalance but without analysis it'd be impossible to figure and could just as easily be too much than too little. Fr'instance constant watering with a very hard water could either increase levels of some element or paradoxically there may be something in the water that binds an element.
I had issues last year early on with my glasshouse... hindsight and I'd probably chucked in too much wood-ash. Replacing a layer and watering with miraclegrow solved that for me and this year it's back to normal.

[chrismahon]

When we bought our last house the soil was very badly depleted having been used for 30 years and nothing put back. We got very poor crops and the root vegetables used to split in the soil. Turns out it was a trace element deficiency (Boron) so we sprinkled VitaxQ over the whole area and the result was nothing short of miraculous.

[farmers wife]

Where are you getting your manure from?  Is it from a farm that is using high amounts of chemicals? Is the compost made by you?  Have you tried the no dig method of laying cardboard muck and greenwaste and leaving over winter? Are you using chemicals in the tunnel?  I assume not.


I am just starting out but I dont think there is anything called soil sickness there is of course soil that is dead and lacking worms and micro life.  Even so laying manure (cow) and compost should bring the condition up leaving it so 6 months you should have an abundance of worms.  If you incorporate enough manure or compost then you shouldnt need to add expensive elements or mess with it all all.


I would def build up the soils and leave it over winter.  Refer to Charles Dowding for mulch methods.

[Fleecewife]

Hi everyone and thank you for your comments    There are some really helpful ideas and suggestions there which have got me thinking 

I've been doing a bit of research and it seems that soil sickness is a problem with large scale monocultures, chemical use etc.
So it's not that.  But there's definitely something wrong.

Farmers wife, I have used organic, no chemical methods all my life, feeding the soil to feed the plants.  We make our own compost from garden waste, and FYM using our own hen house cleanings and sheep droppings. The straw we use as bedding will almost certainly have had chemicals applied during growth, but I had hoped they would have degraded by the time we spread them.  I need to look into that more closely, but thinking, everything grows fine outside (except peas and beans this year  ), using that FYM. I don't know of any chemical free growers of cereals here. There have been a lot of seeded weeds recently so we burn those rather than compost them.  Having in the past found extensive damage due to chemical contamination in broad beans at my brother's farm (the spray tank hadn't been properly cleaned after using weedkiller, before spraying something else - the horrors of chemicals  )  The plants became curled and deformed, and failed to grow properly or crop well, and that's not what I'm seeing here.  A few years ago though I did see something similar in tomato plants in the tunnel, which was eventually traced back to the compost I was using which must have had traces of Aminopyralids.  I've changed my compost, and I haven't seen that kind of damage again.

I use the 'cover it for a year' method in the outside beds.  This year it's in earnest as I can no longer dig at all, so half the garden is covered with a giant tarpaulin bought specially (manure will be spread later) for next year's crops, and the half we are currently using will be covered this winter and next year.   This has worked beautifully for us in the past, giving perfectly crumbly, fertile soil in the spring, which can be planted up with no further working at all.
I haven't used this method in the tunnel though, other than covering bare areas to keep weeds down.  Our normal routine is to dig the whole area (Mr F does that bit), just single digging MGM as we don't have enough depth of soil to double dig - it just brings up subsoil and broken rock.  Then we mantis in FYM or compost, depending on the intended crop, so it's well chopped and goes down as deep as there's soil.  We then dig big planting holes or rows and fill them with water a couple of times before the plants go in, as the soil is very dry after the winter.
It sounds perfect, but clearly it isn't.

The fact that the self seeded brassicas are doing splendidly implies the soil has become alkaline.  I wouldn't expect this as we do add a lot of FYM, which tends to make soil acid, but we also spread wood ash which is alkaline - maybe too much pgkevet.  I think the first thing I'll do is a pH check.  If that's wildly out then it could affect trace element uptake so that's what I'll check for next Chris.

I think being realistic there's no chance of removing the top foot of soil and replacing it.  If that is necessary then it would be easier to move the tunnel onto fresh ground and start from scratch.

To anyone who's read this entire screed, than you and thank you for your replies - there's enough to keep me busy for a while there 

[clydesdaleclopper]

I would stop digging as that destroys the fungal hyphae in the soil which form symbiotic relationships with plants and help to transport nutrients to them. I would also think about remineralising the soil. You could use Rockdust for this or for a more targeted approach I would recommend reading "The Intelligent Gardener" by Solomon which is all about getting the mineral balance in the soil right.

[Fleecewife]

The book sounds really interesting CDC - I'll see if I can find it.

We're kind of stuck with having to dig as we have been invaded with creeping thistle.  The roots go down as far as there's soil, and spread horizontally deep down.  The thistles are undeterred by mulches organic or barrier.  If we try just to pull them out then they proliferate madly.  I agree that digging, ploughing etc destroys the structure of the soil - it also upsets the worms and soil micro-organisms, but until we can get on top of the thistles I don't see what else we can do.
'How to' books on gardening skip over the problem of perennial weeds by their little catch-all phrase - 'first remove all perennial weeds' 

[clydesdaleclopper]

Pull the thistles now. When they are flowering all of their efforts have gone into that and if you put on some thick gloves and grab them at the base some of the root will come up. It is usually enough to stop them regrowing or to significantly weaken them.

[cloddopper]

My friend Don ran the same polytunnel ( with new covers ) for well over 12 years ( till he died of old age )  with great success. he never had any crop reductions far from it ...the longer he ran them the better his crops .

Question ?
If you soak an area with water for 1/2 hr or so & put a couple of square yards of cardboard , , black plastic sheet ,  sacking or some other barrier over it after a few days will you have worms  at the surface or close to it underneath where  it has been well wetted ?
  My old Percy Throwers , " Encyclopaedia of Gardening " published in 1962 says that red spider mite is common in glasshouses ( polytunnels wern't invented till much later on ) is worsened by by a hot dry atmosphere & as a consequence it is very very effective to spray clean tap water  in the glashouse to kill them off.
 At the men's sheds group I go to I set up a Hozelock battery timer with Antelco sprays heads using 15 mm main supply lines and 1/4 " take off lines. I've set it to do programme two which gives five min of fine spray once every 12 hours (07.00 A.M & 19.00 P.M )sessions of 5 min each.
This has cured the red mite problem entirely .
Initially it also started to show red rust on the 10 wek leeks as I'd set the timer to operate in two 15 min slots in 24 hours .
 
Percy also recommends using a sulphur candle to fumigate an empty greenhouse , as it not only knocks mites on the head it also does in lots of other bugs in the empty glasshouse

I feel that if you are perpetually growing inyour tunnel this may be part of the problem of pests moving from one crop to another without being interrupted for a while .

Something else comes to mind if you get a hot day outsidesay in the 80 oF's  inside the tunnel it can reach well in excess of 100 oF .  This is far too hot for most plants in the UK will really knock the  growth and leaving them susceptible to pest & disease attacks .
 Now add in a not quite enough water situation when the plants need it (not when you feel like watering them )  & you have a recipe for disaster. 

 DG Hessayan's , " Greenhouse Expert " is a book I'm happy to recommend for it's how I started our glasshouse ( concrete floor ) seven or so years ago .  The only problem I've  realised I had was the start of a greyish white powdery  mildew , cured by putting a car boot sale electric oscillating fan under the seed bench on a timer set up & switching it on so as to get better air circulation  .
This extra air circulation is also good on hot days when the auto air vents open up & it is still too hot without the fan .
 It cured it and also gives the unintended consequence  that the gentle air movement causes plants to sway ever so slightly and thus they grow stronger stems .

[Fleecewife]

Clydedaleclopper - you've clearly been pondering my problem - thank you.
I bought the mineralising book but I couldn't get past the self-justification bit - sorry.

For the tunnel being too hot, well, this is Scotland and we certainly haven't had any temps anywhere near 80.  Nonetheless, it does get really hot in the greenhouse, although the tunnel is usually ok as it's well ventilated with doors and big louvres at both ends, and lies east-west to catch the prevailing breeze (and it sure is breezy here).  I do wish I could use a fan, but we have neither electricity nor mains water to the tunnel, in fact we don't have mains water, full stop.  When it gets hot in the greenhouse then I have to fan it by hand, and damp the whole place down.  If it's really hot then I would take the pots out, as everything in there is in containers.   For the tunnel, we water a lot, most mornings unless the soil is still damp from the previous day, and we give it a thorough soaking, not just a surface splash.  Plants such as beans, tomatoes, peppers and chillies are sprayed with water twice a day to help flower set and prevent blossom drop.  I think what could help waterwise would be to spray water over the metal bits of the tunnel - hoops and reinforcing bars, in case there are mites hiding.
I do agree that we should try clearing the whole tunnel for the winter so there's no plant material for diseases to survive the winter on.  It would be difficult as all our winter crops have to be grown inside due to the harsh weather.   The soap spray does work against the mites, just not total wipeout as you would get with chemicals.

Earthworms - it depends just which part of the tunnel, and when.  Our garden outside and all the pastures are heaving with earthworms - Darwin would be proud of us.  As a method of weed control, we let the soil dry out completely in the tunnel at times, especially in the winter.  I can see that this has its drawbacks.

Incidentally, the tomatoes have recovered from their scrawniness and are producing well.  As this is a cherry - Sakura - they will go on producing for 2 or 3 months more, so we should get a heavy crop from them 

[Piggerswiggers]

We don't have mains electric to the poly either but we do have a 12 volt fan that runs off a solar panel. It makes a real difference to the air flow and tends to come on when it's most needed I.e. when the sun comes out and the temp in the poly really starts to climb. The poly is 50 ft long so air movement in the middle isn't great even with both sets of doors open and I've found this to solve the problem of that still and damp bit half way down.

[Fleecewife]

Brilliant idea Piggerswiggers     Why on Earth didn't I think of a solar panel  ?  What size do you need to run your 12 volt fan?

[Piggerswiggers]

Hi FW, we've completely over specced it with a 100 watt panel as that was what we had spare at the time. However I've just looked at the back of the fan and it says rated as 15W. At the risk of stating the bl*****g obvious the panel needs to produce at least 15 Watts.

[Fleecewife]

    

I handed the idea over to Mr F who loves stuff like that and agrees it's a great idea, so he has it all planned and ready to order for next summer   

We also have a plan of how to rejuvenate the soil in the tunnel over the winter, so  we have a better year in 2017