About The Long Island Gardener Expertise Do you know the wrong fertilizer will keep your plants from blooming?
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Experience Homeowner with gardens indoors and outdoors, lawns back and forth. I wrote my first gardening column for our college newspaper, teaching roomates about the right way to feed those windowsills gardens. Today I look for challenges. Organic Fertilizers are the key to proper feeding of all our plants. Can you make your own fertilizer? Some people think so -- but there are side effects. I have been there, done that for 54 years and there is nothing like the voice of experience when it comes to Horticulture and Fertilizers.
Publications Numerous and sundry but only in college did I write about plants.
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I have a question regarding soil amendment and hope you could help me with this one.
I would like to decrease the pH soil of some potted plants from 7.0 to 5.0 using H2SO4 (density 1.27 kg/ltr).
How much H2SO4 in ml should be mixed per 1 ltr of destilled water ? How many times of watering with this acid ingredient approximately to reach the target pH ?
The reason behind was that I need more acidic soil for some plants such as rose and hydrangea (blue). Have a bottle of H2SO4 (liquid one litre), d=1.27 kg/ltr, used normally for car battery. Instead of buying Sulphur Powder, I'm thinking about using this liquid H2SO4. If the concentration still too high, the plants will die but if too low then pH will never or change very slow.
Rgds,
Ari
Answer Technically, you are right -- and to put this very simply, you could lower the pH with the method you describe. Electrolytes in lead acid battery cells contain 33.5 percent Sulfuric Acid. It also has a pH of around 0.5 to 1.0. A product we could loosely call Chemical Fertilizer is produced from a 62.18 percent concentration of Sulfuric Acid.
And technically, you can indeed calculate the amount of H2SO4 --Sulfuric Acid -- for a given Soil sample.
And technically, Sulfur is a secondary macronutrient (along with Calcium and Magnesium).
Now for the fine print.
FYI: The Gold-celebrating Russians at Chemindustry.Ru point out: 'As a strong dehydrating agent, Sulfuric Acid reacts destructively with some organic compounds. Thus, starch or sugars, being treated with it, become charred.' Here's their website for your reading pleasure:
www.chemindustry.ru/Sulfuric_Acid_extra_pure.php
Fact is, Sulfuric Acid will merely acidify the Soil before leaching out. Slow, enduring Soil corrections may require patience, but they also buffer your Soil. The pH of the Soil depends not on the pH of the liquid you use, but many properties of the Soil itself. Sort of like the difference between jumping off the roof of a building and taking the elevator. You are not going to like the results of that jump.
BTW are you aware that the Blue in your Hydrangea depends not on pH of the Soil, but on the Aluminum that is freed up under acidic conditions?
Bottom line: If you just have to play with the Battery Acid, find a pH buffer solution with a pH of 5.0. Battery Acid works in theory, but it will dissolve minerals present in the Soil and leave lumps of Salt deposits as the Water evaporates. Yes, you will still be confronting some precipitation if you use a buffer -- but because it's a buffer, pH won't fluctuate wildly.
