As we all know, soil itself is a buffer system. If added some acid solution, soil will buffer and slow down decline of soil pH. And soil pH might be unstable after addition of acid solution for some period.
Now I’d like to change soil pH from 7 or 6 into 5 or 4, and change it from 5 or 4 into 7 or 6, what should I do?
One way is to add HCl or NaOH solution, separately.
Another way is to add buffer solution, which is mixed by Tris (hydroxymethyl) aminomethane, butene diacid, citric acid and boric acid, dissolved in HCl or NaOH solution, separately.
In addition, should I add acid or alkaline solution at a time or add them little by little?
Is there other good way to achieve this? Hope your answer sincerely.
I would be very careful if strong acid (HCl) or strong base (NaOH) are used to adjust soil pH. Upon contacting with soil particles, these strong chemicals may dissolve soil minerals and the whole system would be altered. You may need to go slowly, by adding varying quantities of CaCO3 or (NH4)2SO4 to raise soil pH or to lower it, respectively. Such processes may take 2 to 4 weeks (subjecting the amended soils through 2 to 4 wetting-drying cycles).
Do you want to change soil pH but the purpose should be very clear
even planting flowering tree and allowing sprinkiling water to flow brings down pH
select method based on the purpose
is it for soil amendments, i am in conformity with other answers
To get a precise soil pH value, First you need to get the buffering capacity of the soil. At the acid region buffering capacity shows a linear changes of pH with liming materials. to get a quick result, Ca(OH)2 is better than CaCO3 . When you need to reduce pH elemental sulfur is much suitable. However at the alkaline range buffering curves do not show linearity with acidifying materials in some soils.
Dear Dr Gong: I agree with what Dr Mahesh Suggested above.
I'm however of the opinion that elemental S is more effective in biologically active fresh soils, as is required for S oxidation to reduce soil pH. In air-dry soils or long-stored soil, soil mixed with FeSO4 could be incubated at field capacity moisture (25-40 degree C) for 7-10 days for reduction of soil pH.
In my lab, I tried to modify the soil pH (initial pH 4.5) using CaCO3 and FeSO4. in 10 days, I found a pH range of 3.15 to 8.0. that was enough to serve my purpose.
Thanks.
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