nutrient salts build-up

I have a number of raised beds for veggies. I have had to line the bottom of each bed with a layer of heavy plastic because nearby oak tree roots invaded and sucked up all the moisture. The problem now is that after several years of growing veggies and fertilizing with Osmocote slow realease pellets, I suspect that there is a build up of nutrient salts, since there is very little natural leaching of the salts.
My question is, can I offset that build up by adding dolomite lime to the beds, or do they need to be flushed out to eliminate that build up?

What makes you believe that salts are accumulating?

Well, it's just that each bed has no outlet for water. Plus, it seems that produce from each bed has been declining over the last few years. Most currently, one bed that I planted with okra has been particularly slow to develop. I planted seeds maybe 8-10 weeks ago and even though they all germinated, the tallest of them is no more than 12-15" tall. With our weather, I would have expected them to be 2-3' feet tall by now. In another bed the pole beans should be hanging over the top of the trellis by 2-3 feet. But they are barely 5' tall. Plus, I have Hale's Best cantaloupes planted in another bed and they have been growing as if it was the middle of February.
It just feels like everything is growing very "weakly".

I don't know about the accumulation of "salts". Good draiage is usually considered essential for the types of vegetables you are growing. The problem is that waterlogged soil cut off the oxygen supply to the roots and the plant drowns. In any event adding calcium magnesium carbonate is just adding another salt. It is useful only when you need to raise the pH and add magnesium at the same time. It may be that using the soil as a medium for three or four years while only adding nutrients, that it has become compacted and denying oxygen to to the plant roots. In that event it would be worthwhile to turn over the soil in the beds and add organic matter to hold the soil open.

I think a good soil test would be really helpful to you. It does sound as though the bed is "dead soil," but a soil test will give you numbers on those salts.

Edited to say I missed FDill's post... it's good advice.

This message was edited May 29, 2007 9:11 PM

If the beds are made of wood, you can drill holes around the bottom of the beds about 1" up from the ground. The roots wouldn't get in, but the beds could drain.

Karen

Thank you all for the advice. FD, here in north Fl we don't have soil. We only have sand, so nothing ever gets compacted. And our drought is just as bad as yours, so it's for certain that nothing is waterlogged.
I think I will go ahead and have the soil tested in each bed. Which brings up another question. Do you suppose I could use some of those little ph test strips that I use for testing the water in my above ground pool? I'm thinking that if I use distilled water with a scoop of dirt, stir it well, and then let it settle, it might give me a reliable indication.
And just to be on the safe side, I'm going to follow the advice of drilling a few holes near the bottom of each raised bed to improve drainage. If we ever get any rain it should help flood out any unwanted salts. Any thoughts?

blmlb; Ther is a reason this area is known as the sandhills. Unfortunately this type of sand is sterile, hold no nutrients and water runs through it like a sieve. I am familiar with growing in sand. I use green manures, leaves, pinestraw and anything else I can scrounge to add organic material. I use granular fertilizers, but need something to hold it in the soil untile the plant roots can get to it. I don't use raised beds, but most of the folks who do use artificial soils which I thought might be your case. It does seem that dumping some composted cow manure and working it into your beds might be in order.

Litmus or hydrion test paper used in the manner which you describe will give you a ballpark figure which is all you need. The vegetables that you mention will grow well in apH range from 5.6 - 7.

Thank you, FD. Do I understand that the "litmus or hydrion test paper" you refer to is the same as, or similar to the little ph test strips I use for my "poor man's" pool?
As you well know, it is an uphill battle to maintain a fertile growing bed in sand. And I have, indeed, thrown in I don't know how many of those 40 pound bags of composted cow manure. But they seem to have a limited "shelf life". Within 2-3 years, those bags of cow manure tend to degenerate to nothing more than clumpy dark sand.
FD, I have a tremendous volume of oak leaves that could be worked into the dirt, but I have always hesitated to use them because it seemed that the benefit was offset by the acidity that they produced.
A few years ago I created a mini compost pile of leaves. But to get them to compost, I had to add dirt (sand) along with copious amounts of nitrogen rich lawn fertilizer. Economically, it just wasn't worth the effort.
I do have a benefactor (neighbor) who maintains an extra-ordinary lawn. And she has it mowed and bagged every other week. I carry off those bags of lawn clippings for composting. But what I am composting clearly has a high level of pesticides and fertilizers in it. There just doesn't seem to be a good source of good dirt.
It wasn't that long ago that I used to feel sorry for those folks "up north" who couldn't get a garden started until the snow had melted in mid-April. I no longer feel sorry for them. In fact, I envy them.
They don't have the composting problem that I am faced with year round. They don't have the bug problems and the unending plant diseases that I see from Feb thru Nov. They can grow such beautiful flowers that are unheard of here in the deep south.
And on top of all that, they get a respite from their efforts. They get a real winter. And they get to enjoy a rather "lull season" when they can look forward to, and plan their next garden. Here, there is no dead zone, no opportunity to plan and anticipate.
I'm thinking, maybe it is time to move a bit further north, like to Nashville or Chattanooga. I've been told that those folks have actual seasons. In the meantime, I will continue to fight the pickle worms that are enjoying the hell out of my cucumbers.

Good luck on those pickle worms. They come up here everyyear around the first of July and take out the cukes. They also do a number on young melons and Cushaw pumpkins. Never won a battle with them, but I can work around them most years.

By the way oak leaves work fine, just add a little ground limestone. You can sheet mulch with them which is what I do or grind them and incorporate them directly into the soil. I would not worry about fertilizers, herbicides or pesticides in composted grass clippings. But Florida probably uses Bermuda grass is some lawns, That stuff is murder to get out of a garden plot when it takes hold.

FD, I will remember that. Like I said I have tons of oak leaves. And ground limestone is cheap enough to come by. thanks.

and Gymson also helps rid salt build up. plus it adds calcium to soil.

blmlb - If you used your local "soil" in your raised beds definitely check your soil test before adding lime. My "soil" out here in Atlantic Beach tested outrageously high for Calcium everywhere I tested it. Sarah

thank you sarah.