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...)