The Perils of Growing Tomatoes in Inorganic Clayey Sand

[MelonHed]

An extremely tough lesson learned: Growing tomatoes in inorganic clayey, silty sand, combined with bone-headed overwatering, is a recipe for root knot nematode hell! You may have seen my pix posted two weeks ago here, of some pretty robust Old Italian vines in my jim dandy new heavy duty Florida Weave trellis. In the days immediately following that, the older leaves began to yellow, wither and fall from the plants. The plants at the downhill ends of the rows were eventually decimated, so I pulled them up, and inspection of the roots confirmed the presence of RKNs. I researched the problem and found that tomatoes grown in sand are especially susceptible to these pests: something about air in the pore spaces and the absence of decaying organic matter, combined with high temperatures, being a prime incubation environment for root knot nematodes.

Of the 10 vines I started with, I have pulled up 3, and expect to lose 4 more. As you can see from the first 3 photos here, they are still bearing abundant fruit, but I don't imagine I will see much more than what is coming ripe right now. There are 3 plants at the extreme uphill ends of the rows (photos 4-6) that seem to be relatively unaffected, but I wouldn't be surprised if the worms weren't already there as well; just not in large enough populations to visibly damage the vines yet.

What is interesting is that although I am watering only once every 14 days, core samples taken between the vines indicate damp sand below 2 inches, 2 weeks after watering! There has been no significant rainfall for a month now, and the temperature has been in the mid-to-high 90s every day! There is apparently just enough clay to retain moisture through pretty adverse conditions, but I find I must be very careful not to overwater.

Also, I have two rows of Cherokee Purple which seem to be unaffected by the nematodes. The older row (photos 7-9) were planted in 10" x 18" post holes filled with Miracle Grow potting soil, so perhaps the decaying organic matter is protecting them, but the youngest row (photos 9-12) is planted naked in the river sand, amended only with Shultz's Plant Food, as are the ailing Old Italian vines. I wouldn't be surprised if they are still unaffected by virtue of their being planted last of all, and the nematodes are there, just building up their population...

All I know to do is prepare for these pests next year; all I can do this year is keep my fingers crossed. Any advice would be greatly appreciated!

(Sorry about the poor quality of these pix...My wife has the good camera on vacation...)

[TZ-OH6]

Bummer,

Canadian researchers used uncomposted chipped branch wood (hardwood) [ramial wood chips] as a soil ammendment in depleated african soils and it supposedly cleared up the nematodes. Unfortunately I can't find the research paper, only annecdotes in their other publications. I suspect the biological activity associated with in-situ decomposition directly affects the nematodes in a way that pre-decomposed compost does not.

[MelonHed]

Thanks! That makes more sense than what I was planning on trying next year: 2 rows with French Marigolds planted all around, and 2 rows of "nematode-resistant" vines. For one thing, I really don't want to grow ornamental flowers (I can't eat them!), and for another thing, none of the so-called "nematode-resistant" varieties seem like particularly interesting fruit.

I saw I guy on YouTube growing a massive "tomato tree" in a pile of rotting garbage. Must be the same principle.

[TZ-OH6]

The pile of rotting garbage would be mostly organic material-compost. Nematodes need loose sand grains to move around, so the high organic content screws them up by getting in their way. The wood chips are not used that way, less than 2 inches of wood chips are mixed into the top 3 inches of soil, with a little forest topsoil to inoculate it with the natural soil forming microbes. There is a little nitrogen deficit the first year (so just fertilize a little), but after that more chips can be added every three years with no more nitrogen problems.

This sets up a natural soil making microbial community, slowly feeding on the wood, that retains and recycles nutrients long term within the living organisms, whereas compost is more of a slow release fertilizer that gets depleated in a season or two.


I'm a biologist, not a rabid bandwagon riding organic gardener so I'm not going to say its a magic bullet, more of an economical soil reclamation method. Spreading manure or compost every year will get you better yields, but if you have poor soil, it will help make it better.

Like I said, I haven't found the nematode report so I don't know exactly what happened with that, only that other papers on "ramial chipped wood" say the nematodes disappeared. I don't see how the microbes in the top layer of the soil could have affected subsurface nematode populations though, unless it was a good environment to breed nematode predators, maybe predatory fungal species. Cultivated soil is notoriously low in fungal diversity compared to forest soil (because of the lack of a long lasting food supply -such as wood- and the effect of tilling chopping up their little fungal bodies.)



www.uvm.edu/vtvegandberry/Pubs/Wood%20Chips%20in%20Vegetable%20Production.pdf

http://cat.inist.fr/?aModele=afficheN&cpsidt=13997770

[organichris]

I'm doing the pile of rotted garbage thing this year, and it simply works amazingly. My Jetsetter tomato plant is well over 7 feet tall right now with no end in sight. It has plenty of tomatoes and is still blooming like mad. I haven't had any ripe tomatoes to eat yet, but I should within the next two to three weeks. I'm anticipating a very nutritious and flavorful product.

The video MelonHed mentioned is of L.A. Rotheraine. His website is rotheraine.com. I think he gets amazing results not only from the garbage method but also the good genetics. You can buy seeds from his company, and I think they'll even send you some for free. They have a astrological view of farming that's a bit strange to me, but you can't argue with results.

[MelonHed]

Thanks, guys! Live and learn! These findings are extremely interesting to me, especially the practice of top-dressing with the wood chips, rather than turning them into the soil, and the idea that tilling the soil is not always a good thing...

Chris—I would love to see a photo of your Jetsetter plant.

[dice]

Decent survey of nematode control methods:

http://attra.ncat.org/attra-pub/nematode.html

It doesn't include wood chips specifically, but it does mention
compost and healthy soils with plenty of organic matter as an
aid to minimizing plant parasitic nematode populations.