[Homestead] Rotation, was Re: Tomatoes, to rotate or not to rotate

Clansgian at wmconnect.com Clansgian at wmconnect.com
Sun May 4 20:53:37 EDT 2008


>James, you posted that  
you bought a lot of seed potatoes. Did you do that rather than using  
your own because the seed potatoes are certified disease free?

Not primarily, it's a fringe benefit.  I buy them because they are so 
damnably cheap.  Here a 50# sack of the varieties I mentioned cost right around $10.  
You could easily buy the seed potatoes to eat at that rate.

And no mistake, you get better yields from virus free (notice I didn't say 
disease free necessarily) potatoes.  But have you considered this, shades of 
Monsanto, that we are setting the bar in the wrong place?   That is, if you keep 
spuds from the virus free crop, the yield the next year will be less, happens 
every time.  But as time goes on the potatoes adapt and the yield goes up, 
never back to the levels of the original crop, but respectable.  Here's the 
mental trick being played on us:  this crop after several generations is the NORMAL 
yield for potatoes.  The commercially bought seed potatoes give an exagerated 
yield which we have become conditioned to think of as normal and to feel 
cheated if we accept less than that.

I have some all blue, all red, caribe, kerr's pink, yellow Finn, and some 
others growing in the garden from seed spuds at least ten generations from the 
original virus free stock.  The yields are more modest but not nearly enough to 
offset the cost of those very expensive seed potatoes.  They DON'T cost $10 
for the sack!

It's normal for potatoes (and raspberries, and strawberries, etc) to 
incorporate viruses into their DNA and go on.  The yields drop some from those 
exagerated yields from the new plants, but not so much as to lose sleep over.

If the yield drops 30% over time (it doesn't, but suppose it did), a 
commercial agribuisness farm with a 10% profit margin would be wiped out and in the 
hole.  But if I get 700 lbs instead of 1000 lbs, so what?  Different world with 
different rules.


>But potatoes do  
benefit from calcium. I have never figured out how to resolve this  
paradox. I have read that some commercial growers provide calcium  
chloride during the growing season. My mindset is that as long as I  
provide large quantities of mulch and compost, the soil community will  
take care of the rest of it.

The calcium chloride (road salt) bit works, but I am absolutely convinced 
that you are right about the compost.  When I have adequate compost available for 
a plant, I've never seen the first signs of deficiency disease in them, no 
matter much the origin of the compost.  Compost is living and self regulating.  
I have a lot of wood ashes from maple which adds calcium and potassium (in the 
forms of calcium and postassium oxides).  Even that is a bit of an overkill, 
but it will counter act the effects of acidic decomposing compost quite well.

> >That may very well be. I believe there are, however, sound reasons for  
> garden rotation.

There are, and I do quite a bit of it myself.  My mico-plots are my favorite 
crop rotation technique.  But  I think it is little understood.   A lot of the 
root diseases only diminish after five years or more without the host.  Think 
of how few genera our food plants come from.  Potatoes, tomatoes, peppers, 
and eggplants are all one genus.  Not only are cabbage, broccoli, cauliflower, 
Brussels sprouts, kale, collards, kohlrabi, broccoli rabh,  all the same genus, 
they are the same species as well!  Beets, spinach, and chard are the same 
family (Chenopodiaceae) and so is the comon wild lambs quarter in many of our 
gardens.  All the new world beans are the genus and most are the same species.  
Peas, fava beans, and lentils are closely related, as re onions, leeks, and 
shallots (obviously).  All pumpkins and squashes are the same genus, etc. etc.

That is, to rotate off these families and genera of plants for long enough to 
attenuate the diseases is impractical if not impossible because at best our 
gardens aren't all that biologically diverse.

Not saying there's nothing to crop rotation, but that it isn't as simple as 
the common gardening literature portrays it.


James



 Root diseases tend to diminish when deprived of their  

> hosts. The roots of some crops till the soil and bring up  
> micronutrients. Crop residue may hold disease organisms. Just as I do  
> not leave fruit tree prunings lying on the ground under my trees, I  
> prefer, when I have time, to compost crop residue. Many crops benefit  
> from raising the pH with lime: legumes, brassicas, tomatoes, peppers  
> and more. But I would not follow a liming year with potatoes, so as to  
> plan against scab, which, while not especially damaging to the tubers,  
> causes most of us to peel and therefore waste the product. Yeah, I  
> know, just grow more. But I also do the cooking in our family and I  
> consider potato peeling a waste of time and nutrients. But potatoes do  
> benefit from calcium. I have never figured out how to resolve this  
> paradox. I have read that some commercial growers provide calcium  
> chloride during the growing season. My mindset is that as long as I  
> provide large quantities of mulch and compost, the soil community will  
> take care of the rest of it.
> 
> For those of you who grow potatoes, do you use the same area for  
> potatoes from year to year? To what factors in your garden do you  
> attribute greater or lesser incidence of scab? James, you posted that  
> you bought a lot of seed potatoes. Did you do that rather than using  
> your own because the seed potatoes are certified disease free?
> 
> The one factor of which I am certain is that constantly working to  
> raise the organic content in my garden is beneficial. The end product  
> of adding organic matter above and into the soil is humus, which is  
> the final state of plant matter, the state where the soil community is  
> happiest. That organic matter also creates oxygen pathways and holds  
> moisture during periods of inadequate rain are bonuses. The biggie for  
> me is providing optimal conditions for the gazillions of microscopic  
> and visible animals living below the surface of my garden beds. 

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