Advise on soil ph issue...

I thought a soil mix of 1/3rd compost,1/3rd coco fiber, 1/3rd perlite with a cup of dolomite lime per 3 gal. container would provide an excellent medium. Prob. w/ph is around 5 or so.
Water's neutral at 7. Any thoughts on how I might correct or bring ph up to better level without harming plants.

water is fine once you add nutrients it will prolly balance out just check your runoff water after watering

nutes will most likely lower your pH even more.

hmm maybe .. you might wanna try some more lime to bring the ph up ?

Lime will bring the pH down. It is acidic which corresponds with a low pH. A high pH is basic. Fallen-I think you are thinking along the right lines but backwards with the numbers.

Thanks, but soil is reading like the ph is around 5 and month old plants are beginning to get some yellow leaf curl on first/second leafsets. Slower than normal growth. Can I powder some dolomite lime and add to water or you think 1/2 teaspoon of baking soda would be better. Have limited access to any other ph up
products here in central america.

Lime is basic,.. takes the pH up. Dolomite is added to counter the acidity of the compost. Sometimes compost is more acidic than the stuff used in the recipe and you need more dolomite. Don't expect your watering solution to bring the pH up if the soil is buffered. Unless your'e adding a bunch of nutes, the watering solution isn't buffered.

So add more Dolomite. Take a gallon of your soil,.. add some dolomite (teaspoon to a tablespoon) mix and then take a quarter cup of that soil and add a cup of water. Mix well,.. let it sit for a while ten minutes is good,.. an hour is better,.. mix again then take the pH. This will tell you if the amount you added was too much or too little,.. calculate it out and add that much dolomite to the rest of your soil.

Actually, lime is neutral, not a base.

Siddhartha said:

Lime is basic,.. takes the pH up. Dolomite is added to counter the acidity of the compost. Sometimes compost is more acidic than the stuff used in the recipe and you need more dolomite. Don't expect your watering solution to bring the pH up if the soil is buffered. Unless your'e adding a bunch of nutes, the watering solution isn't buffered.

So add more Dolomite. Take a gallon of your soil,.. add some dolomite (teaspoon to a tablespoon) mix and then take a quarter cup of that soil and add a cup of water. Mix well,.. let it sit for a while ten minutes is good,.. an hour is better,.. mix again then take the pH. This will tell you if the amount you added was too much or too little,.. calculate it out and add that much dolomite to the rest of your soil.

Click to expand...

BigBudBalls said:

Actually, lime is neutral, not a base.

Click to expand...

That's wrong. It's alkaline. Try putting some in a cup of water and testing the pH.

There are a lot of different types of lime,.. but I've never seen an agricultural lime that wasn't basic. Hydrated lime will give a pH over 11 if you dissolve it water. Some hydrated limes will go over 12. The different pH's are due to the differences in solubility of the type of lime. Most agricultural limes are hydrated.

If you take dolomite lime put it in water a water with it I will bring the PH up or down to 7 very true look it up I had a high PH watered with dolomite and it buffered it to around 7 give or take.

if your tap water is ph of 7 , just flush thoroughly with your 7.0 tap water and test ph of water run off every couple of minutes untill your where you want to be. this just happened to me. Ive found that certain soil materials can turn acidic after sitting for a period of time. Its the biological composition still taking place within the soil mixture. Trust me, flush for a while with your tap, youll thank me.

Lime is alkaline. Dolomite can be a different story.

Agricultural lime is used to RAISE the pH of soil.. it is used to LOWER the acidity of soil. That means it's alkaline or at the very least a pH over 7. I think some folks are misreading those statements when they read the facts, and think it raises the acidity.

Slaked or hydrated lime will raise the pH the most and quickest. It contains a high level of Calcium hydroxide. Other forms of lime contain mostly calcium carbonates with some calcium hydroxide and calcium oxide.

JRod,.. I'm sure you did put some dolomite in a glass with some water and stuck a pH meter in it and measured 7. The fact that it reduced pH in your case is incidental and I can't imagine that it would normally be used for that because it's not good at it. It's much easier to use a few drops of citric acid or lemon juice.
But tap water is not buffered at all, whatever was in your dolomite reduced the pH. Tap water pH is high usually only for one reason and that is high levels of alkalinity. Some municipalities add it to prevent corrosion. Dolomite is carbonate based,.. which is alkalinity, which is part of the reason why your tap pH is high. Adding carbonate to lower pH doesn't make sense, unless it's over 8.4 coming out of the tap. Even in that scenario.,. carbonates are so insoluble I'm not sure you'd see much of an effect from carbonate alone. It dissolves more in acidic solutions to make carbon dioxide and water.

Dolomite is called that because it contains magnesium carbonate as well as calcium carbonate, but since it's collected from mines,.. and not processed much, it has a variety of constituents, and isn't entirely consistent from mine to mine and some can have higher levels of sulfates and lower levels of bicarbonates. BUT even carbonates, which dolomite is, buffers pH to about 8,.. if you let it dissolve enough,.. bicarbonates buffer to around 8.4 (if I remember right) and hydroxides go to 14. The magnesium or calcium have no affect on pH.

pH is a direct measure of hydrogen ion concentration or H+ It is the inverse log of the hydrogen ion concentration. that means each unit you go,.. is a log change in concentration.

Things that react with H+ are carbonates which if allowed to dissolute,.. will make carbon dioxide and react with the H to make water. Carbonate = CO3 so if allowed to dissolve> CO3 + 2H = CO2 + H20
bicarbonates pretty much do the same thing,. only they're HCO3 and they make CO2 and hydroxides.

Carbonate chemistry and pH isn't easy to understand and I'm no expert,. But when "looking it up" I can't find a site that isn't a stoner forum,.. that says use carbonates to reduce pH.

Oxides are virtually insoluble.
Carbonates are hardly soluble,.. I mean you're lucky to get a couple hundred ppm,.. and buffer to pH 8.
Bicarbonates are relatively soluble and buffer to pH 8.4ish.
Hydroxides are very soluble and since they react directly with the H+'s and very rapidly, the pH is basically limited to the solubility of the material.

Wow,. sorry for that ramble,.. I was watching TV while writing it. (and smoking)

Ha, and here I thought the first mention of lime was referring to actual limes...

Taking a horticulture class or picking up a gardening book will usually help out with any soil problems/issues you may have

tdiddy said:

Ha, and here I thought the first mention of lime was referring to actual limes...

Click to expand...

LMAO,... That's funny. Lime juice would definately lower the pH,..

That's a lot of dolomite lime----and it takes a while to go to work----you should see a raise in PH of the run-off. Is the mix new or have you been using it for awhile? note: 1 Tablespoons of dolomite will raise the the PH from 5.5 to 6.5 in 1 gallon of soil. It takes 4 days to raise the PH and the effects will last about 4 weeks with average water and nutrient applications. Dolomite lime also releases Calcium and Magnesium which are assimilated by the plants and needed.