Your results and the agent's response leave me with more questions than answers. I really do not understand at all the agents response to the results you posted above.

First, what are you trying to grow, or want to grow? That is a key determinant of where you want soil pH to be. If you want to grow potatoes you're okay, and a tad lower wouldn't hurt. If you want to grow tomatoes you want it a bit higher. So what do you want to grow?

Second, are you sure about the potassium number (107) and the "very high" descriptor? At 107 ppm it looks midrange to me, not very high.

Ca, Mg and P are all okay, but raising the Ca and Mg levels if lime is need for pH won't be a problem.

Soil pH is determined predominantly by carbonate euqilibira, not by Ca or Mg. Ca and Mg are the most common associated base (carbonate) cations. While important as plant nutrients, as a matter of pH they come along for the ride with carbonate. They also come along with other anions, like sulfate. Consider gypsum - basically calcium sulfate. Adding that to your soil will raise the calcium level but not the pH (no carbonate). Adding lime (calcium carbonate) will raise the calcium level and the pH. Adding dolomitic lime will raise both calcium and magnesium, and the pH.

When you say "It did okay with some things, but struggled with many other items", what items did okay, which ones struggled, and what does struggled mean? How did you manage nitrogen? What's the soil texture like - is it mostly clay like or is it mostly sand like?

Thanks for the response! I am trying to grow a variety of vegetables including tomatoes, sweet peppers, cucumbers, cantaloupe, okra, eggplant, green beans, southern peas, winter squash (various) and cut flowers.

Typo on potassium. It is 197.56. Sorry!

Last year tomatoes, cukes, cut flowers, southern peas, winter squash and cantaloupe all did fine.

Green beans made plant and fruit but both seemed stunted. Okra, same thing. Poor yields on both, as well. Bell peppers yielded well but were small and plants seemed stunted, as well.

The soil is classified as silt loam on the soil test. It contains a lot of clay. For nitrogen, I used pelletized, composted, chicken manure 3-2-3. 100 lbs per quarter acre. I foliar fed weaker looking plants with a fish fertilizer listed as 2-3-2.

Okay, 197 is high. Now that makes some sense.

I think the two biggest issues you're facing are pH and N.

For what you're growing pH should be in the 6-7 range, and shoot for 6.5. You need lime. You can use dolomitic if you want to, but it's not necessary. Don't be surprised if you need to do this again every few years. Did LSU give you a lime recommendation?

N - 100 lbs per quarter acre of 3-2-3 is 3 lbs of N per 11,000 sq. feet. That's pretty low. I believe if you consult some plant nutrient demand references you will find you probably need about 3X that amount. For N I would stay away from the manure stuff - you're adding as much K and nearly as much P as N. Do that over time and you may start to see some other problems. Given your mineral nutrient profile you want as clean an N source as you can find for at least a year. Bloodmeal if you want to stay on the organic side or urea if not would be good choices.

Some additional thinking - did you have micronutrients or soil organic matter tested? From LSU the only thing micro's will add are iron and manganese, but you should at some point check those as well.

If after dealing with the pH and N issues you see what appear to be the same problems continuing over time, you may need to look into plant disease or pest issues, but not now.

High Mg can bind to clay/silt particles and outcompete other cations for holding/exchange because of it's ionic radius.

If you think of nutrient attraction as you do elements, with the proton/neutron + electron orbits forming "little planets"...well, Mg forms a tight/small orbit which both holds tighter and has less overall area to be bumped/replaced by other cations. Compared to other nutrients competing for holding/exchange sites that are attracted by negative sites (and some positive sites) on clay/silt, Mg can be thought of as a "stronger magnet" for both attraction and holding...kinda.

The nutrients, themselves, are actually hydrated (surrounded by H + H2O) so there's a little more to it than just the bare elements, but that's basically how competition between charged particles happen.

The Mg is hard for many other cations to replace, therefore they stay in the soil solution, unbound, or leech out below the root zone depending on the soil type and moisture.

So basically, high Mg levels can lead to depletion of other nutrient cations by leaching, if the level is high enough relative to the soil's cation exchange capacity. Mg at high levels doesn't bind other nutrients making them unavailable, but excessive soil Mg levels can lead to very low levels of other nutrient cations. That could further be exacerbated by high acidity. I don't, however, believe at 250 ppm Mg that would yet be a problem, and if it were there should be other symptoms of various nutrient cation deficiencies, such as chlorosis.

tdaigle - if you haven't already take a look the the LSU Ag Center Soil Recommendation Sheets. Specifically, look at G-707. That explains nutrient needs (mostly N for you) for three categories plants along with timing / frequency based upon your soil test results from their lab. Be sure and read the fine print (Note) at the bottom of the table. You can sub any about any available N fertilizer source for their recommended fertilizers (their's is based upon water soluble N, so a bit of consideration of slow organic sources may be needed). The idea is getting the amount and the timing right.

If after looking at that sheet you have question about how much vs. type, ask and we can work through the calcs, explanation, etc.

Thanks,TXEB. Fascinating stuff info on the mg! Regarding lime, I prefer to use the pelletized type as it is easier for me to spread. My sample said one ton per acre would get me up to 6.65 pH. But I've read conflicting information about how much pelletized lime to add. Some say you need less of it than pulverized lime. Any thoughts on this?

You really need to know the calcium, carbonate equivalent (or neutralizing efficiency) of the lime you're using, and also consider how deeply it will be mixed . Deeper means more soil getting treated so more lime. LSU's recommendation is probably based upon a 6" soil mixing depth, Michigan uses an 8" 9" depth. You might check with your county agent on the basis for the recommendation if it's not explained in your test results.

It's really more a matter of the amount of calcium carbonate than it is speed - it's the end, equilibrium result that should be your focus.

Pelletized is fine, and reacts about the same as the fine ag lime. Just get the calcium carbonate equivalent and adjust accordingly. They can vary quite a bit. Check out the link below.

edit - a bug in my head led me to go back and check - MI bases their conventional ag field crop lime recommendation on a 9" depth, and uses a 3" depth for recommendations on established sod, all for a neutralizing efficiency of 90%, which is the average for lime sold in that state (very different than KY's 67%).

Here's another good reference from Missouri on lime that may help.

Here is a link that might be useful: Pelletized Lime

This post was edited by TXEB on Tue, Sep 24, 13 at 8:39

tdaigle - a discussion in another thread about stunting of plants reminded me ... a couple of questions:

- about when (month / week) did you notice the stunting / poor growth and lower yields of the plants affected?

- in what part of LA are you growing?

- do you have sodium (Na) results too?

BTW - silt loam is pretty low on clay (0-28 %), but is quite high in silt (>73%), which would be consistent with what your test results are suggesting about your soil's cation exchange capacity.

TXEB - thanks for the info on the lime. Soil test said if I added one ton to the acre pH would be 6.8. A little too high. Will cut back to about 2/3 of that recommendation to shoot for 6.5. Don't know much about CEC of the lime available but will find out.

In regard to your earlier question, I think some of the stunting was a result of a very wet, cold spring (for Southwest La.) and poor drainage. But on some crops, like the okra and bell peppers, I noticed the poor growth and yields around May and early June. For the green beans, I noticed it around April for the first planting and May for the second. Both plantings were total duds. Didn't harvest a single bean (that I would eat or sell).

Sodium test was fine: 43.27 ppm

Thanks, that pretty much completes the picture for me.

Your soil is pretty low in clay and has a low cation exchange capacity. That means it will tend to loose nutrient elements / minerals rather easily. Don't be surprised if you find yourself fighting a persistent battle against low pH. Here's one more reference, from the Aggies on soil pH and lime - it's the one I was looking for earlier had trouble finding it. I believe it provides the clearest explanation out there on the proper use of lime. Acidic soils are unusual in TX, except for the eastern side next to LA, which is where this article comes from.

The long-term solution for your low CEC silty soil is to build soil organic matter, but even that may be a bit of a struggle. On building soil OM be cognizant of what you're adding and what it brings as nutrients, especially P. But your soil will be more forgiving than most. You have some freedom that I don't have on heavy, fine-textured clay.

I suspect you're partially right about the wx effect on your plants, but also suspect that on your legumes pH played a significant role as well. We had the cold spring, with frosts and freezing temps right through 3/25 - about 3 weeks past statistical norms. I put up a row cover in early March and kept it there until 3/27. LA had he rains that we didn't get.

I think once you get your pH near 6.5 you'll be doing fine. Building soil OM will help stabilize everything and make it easier to maintain mineral levels, and in turn pH.

BTW, with that acidic soil you're in great shape for potatoes (I can't even think about them), and maybe blueberries and other acid loving crops. You might want to think about reserving some space to allow to remain on the acid side for some "specialty crops".

Thanks, TXEB! Learned a ton! Will follow your advice.