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Re: [compost_tea] in-furrow soil insect prevention?



Why would wet sugar make a hostile environment for any insect? 

Consider what we know about sugar, kelp and lignite added to soil.  Is this a sufficient set of conditions to have teh desired result?  

No.  These additions will not work under certain conditions.  When will addition of these things be sufficient to have the desired effect?  You need to understand something more than just adding sugar, kelp and lignite.  

Do you have to add all three?  And how much? You need to understand WHY they MAY have an effect.  What are the conditions that allow for success, what conditions mean no benefit should be expected?

Simple sugars are bacterial foods.  As bacteria grow using the excess simple carbon that was added, they suck up all the other nutrients, like N, P, S, etc.  You get an area where anything else needing these nutrients is SOL.  Bacteria win in competition with anything else when they have enough simple sugar.  Of course, you have to have decent bacteria, so an inoculum is a good idea (as in good aerobic compost), especially in chemically treated soils.  

Add enough sugar, you'll kill your plants simply because there are no nutrients left for them to grow.  What is the right amount of sugar?  Kelp is added to provide nutrients, but what's the right balance?  

The nutrients in kelp supply which set of organisms with nutrients?  The bacteria and fungi.   Plants can't access the nutrients in kelp material.  How do you get the nutrients in kelp into a plant available form?  You have to have the protozoa, nematodes and microarthropods present to allow that to happen.  What's the right balance of bacteria and fungi, and protozoa, nematodes and arths?  

Where can you find out this information?  Soil Foodweb.  The Soil Ecology Society.  Applied Soil Ecology.  Biology and Fertility of Soils.  Univ of Georgia's Soil Ecology program.  

But think about this - if you add enough sugar, the soil in these areas will go anaerobic as the bacteria grow and use up the oxygen.  

If you have wire worm, cut worm or other obnoxious pests, you might be able to drive them away, since these pests need some oxygen.  But then the soil is anaerobic.  Bad news for seed germination and root growth.

Will the soil stay anaerobic?  Depends on the health of your soil.  If you have good soil strucutre, then life will be ok, as the oxygen returns, the normal set of organisms will revive and life goes on only a little hammered.  

But what if you don't have good soil structure?  Then your seed is in trouble.  You might even say, "See, the cut worms and grubs are hurting the seeds" when in fact the pests have been driven away from the seed by the anaerobic conditions and aren't responsible for this damage.  

What if the soil is anaerobic only in the zone you added the sugars?  Then the pests just go a little ways and hang out until the root arrives.  And the root may be weakened from the anaerobic conditions.  

These pests also like reduced oxygen conditions (how reduced? Probably in the range of 5 to 6 ppm, but I don't know of any hard data on this - does anyone?).  Why do the pests like the reduced oxygen conditions?

The bacteria that grow in aerobic conditions make the environment unpleasant for these pests.  If you are careful to add only enough sugar to help the beneficial bacteria, soil structure will be improved as these bacteria make glues, form microaggregates, and help oxygen diffuse more rapidly into the soil.  The critters that eat the pests move back into the soil.
Get some fungal and bacterial species that prey on the pests to grow - but they require aerobic conditions, or at least not-reduced-to less than 6 ppm oxygen.

What does the kelp do?  Micronutrients, some plant growth factors (which the bacteria and fungi consume quite rapidly, probably long before the factors make it to the root.  If the soil is healthy, the bacteria and fungi that these things grow are probably the real answer to why kelp growth factors work well).  Kelp also contains all the foods normally in plant cytoplasm, and so good growth foods for bacteria and fungi.  Probably more bacteria than fungi, but some really great fungi.  So, the nutrients are made plant-available because the biology is functioning.  

Lignite is a source of very complex foods for the fungi.  Only after fungal enzymes start chewing on the lignite will any bacterial food be released.  Which fungi and bacteria grow on these materials?  There's a whole area of research that needs to be addressed, and people are addressing it.  SFI is part of that work.  

So, again, is too much of these foods are added in, the soil can be driven anaerobic as the organisms start to grow faster than oxygen can diffuse into the soil.  If the soil has good structure, then this problem is less likely to occur.

I had to laugh when I read something the other day that said that molasses or sugar causes root-feeding nematodes to explode.  Really?  And what's the mechanism there?  Root-feeding nematodes have no mechanism to take-up sugars from the soil solution.  They eat plant cellular liquid.  Sap-suckers, if you will.  They like reduced oxygen conditions.  They have thick cuticles that prevent bacteria from having much affect on them.  Could root-feeders get drunk on the alcohol produced when lots of sugar is added and the bacteria and fungi (yeasts) grow?  Maybe that's the mechanism.  But some data on that would be useful, because then you would need to know that sugar addition only works on root-feeders when the soil is badly compacted.  

Please, make sure you understand that I'm trying to point out lack of knowledge here - do not go around saying that Elaine said alcohol kills root-feeders.  We don't know that.  

I'm saying we need to know the mechanism by which SOMETIMES molasses addition reduces pests.  It does not work in all cases, and until we understand WHY it works sometimes, we will never be able to predict when additions will work and when they will not. 

It isn't appropriate to claim that sugar kills pests, because there are many conditions where it doesn't work.  When does it work?  We need to understand these things first, or these statements lead people to believe that organic ag, or sustainable ag, does not work.  

So, to understand when this group of soil amendments have an effect on soil pests, you need to understand the life in your soil. 

Elaine Ingham
President, Soil Foodweb Inc.
SFI Corvallis, OR
SFI Port Jefferson, NY
SFI Lismore, NSW, Australia
SFI Hilversum, The Netherlands
SFI Cambridge, New Zealand
www.soilfoodweb.com

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