In chemistry, pH is a scale that ranges from 1 to 14 and is used to specify how acidic or alkaline a substance is. Acidic solutions have a lower pH number, while alkaline – or basic – solutions have a higher pH number. If the pH level is exactly 7, such as that of pure water, it’s neutral. Soil with a pH of 6 is ten times more acidic than soil with a pH of 7. If your soil has a ph of 5 and an alkaline soil-loving plant will be planted there you need to learn how to raise pH in soil fast.
This guide is focused more on smaller areas of soil rather than full-on fields.
Different types of plants need different levels of soil pH to survive and thrive; plants can only absorb nutrients that are dissolved in water, and if the soil pH is too high, or too low, the needed elements and compounds may remain insoluble or incapable of being dissolved.
Soil pH varies from region to region and from one garden to the next. Most plants need a pH that is slightly acidic (between 6.0 and 7) but others – ivy or flowering vines like clematis and jasmine, and dark, leafy, green vegetables as well as cruciferous vegetables, asparagus, and squash – prefer slightly alkaline soil conditions and will thrive at pH levels up to 6.5 to 7.5.
Another reason to increase the pH level of the soil is that if you have lead or other heavy metals that tend to be more mobile in acidic soils, raising the soil pH can make those minerals less mobile, and less likely to be taken up by plants.
Once you’ve chosen what you’ll be planting, it’s best to verify the soil’s current pH level before making any adjustments. If you find your soil pH is too high – read my article How to lower pH in soil fast
How to raise pH in soil fast
To increase the pH level of your soil, you should introduce alkaline material, known as a base. Applying these products to your garden is known as liming – probably because the most common method of raising the alkalinity of soil in the past was to add crushed limestone to the soil.
How can I raise the ph of my soil fast?
There are several ways to raise the soil pH, at various price points and difficulty levels. Some will work quite quickly, while others may take longer to affect the pH level.
Baking Soda to raise soil pH
This is one of the easiest, most cost-effective, and fastest ways to increase the alkalinity of your soil. Since you probably already have baking soda at home, you will not have to buy any further soil amendments to raise the pH level. Baking soda provides a rather convenient solution – especially if you need a quick fix.
Take a look at this baking soda (bulk) to see if it suits your needs – Baking soda – bulk container
How long does it take to raise soil pH?
Baking soda is cost-effective since it is not expensive to buy, even in bulk – It also produces almost immediate results; in fact, there can be noticeable changes in the soil pH in less than 24 hours provided you use the baking soda properly.
If you use baking soda to increase the alkalinity of the soil, you will never have to worry about harming it – or the growing plants. Baking soda is far more gentle on soil than other compounds and can be applied even when the plants are already growing.
Although there are more potent liming agents that will offer you long-lasting pH changes, they may be more expensive to buy than baking soda.
Wood Ash to raise soil pH
If you’d prefer an organic way to make your soil less acidic, you can use wood ash over the soil and mix it into the top 6 to 8 inches of the soil.
While this method can be highly effective if done properly, it’s easy to oversaturate the soil with ash; in fact, if you add more than 2 pounds of wood ash per 100 square feet of soil per year, you risk interfering with plants’ ability to take in nutrients.
If you want to raise soil pH significantly, then it is best to introduce wood ash very early on, before planting, and not rush the process.
You should plan periodic, small applications over several years, but it can be very effective, as well as a great way to recycle wood-burning fireplace ashes!
Oyster Shell Lime
This finely ground soil amendment is entirely organic as it’s composed of oyster shells from the seafood industry. As it can contain up to 39% calcium, oyster shell lime can be used to correct calcium deficiencies while raising pH levels.
This product breaks down very quickly and is far safer for plant health – and human health – than hydrated lime products. You should apply 2-4 tablespoons of oyster shell lime per plant or 50 lbs per 1,000 square feet, depending on your original soil analysis and the requirement of your chosen crop.
Have a look at what others have to say about this 25lb bag of oyster shell lime by Down to Earth Organics
Dried and pulverized eggshells can be an excellent soil additive; this kitchen by-product is an excellent source of calcium. It will also reduce the acidity of your soil if 1-2 pounds per square foot are added.
Also known as calcium magnesium carbonate, dolomitic limestone is one of the most common soil amendments for raising soil pH and is used by both organic and conventional farmers. It should not, however, be used in soils with adequate or excess magnesium.
While plants need magnesium in small amounts, excess magnesium can stunt plant growth and kill vegetables. Should a soil test indicate that the soil contains adequate or high magnesium levels, use an alternate calcium source for changing soil pH. Read more about Dolomite lime
This soil additive is made from pulverized limestone or chalk and, while its primary active component is calcium carbonate, additional chemicals found within the compound will vary depending on the mineral source but might include calcium oxide, magnesium oxide, and magnesium carbonate.
Unlike other types of lime such as quicklime (calcium oxide) or slaked lime (calcium hydroxide), powdered limestone does not need to be burned in a lime kiln; it only requires milling.
Hydrated pulverized limestone is the fastest-acting alkaline soil amendment, but it is extremely easy to overdose. It can burn plant roots easily and should be avoided by all but the most seasoned gardeners.
As with all lime products, hydrated lime will work much better if it can be worked down into the soil, rather than left on top.
Summary of products to raise soil pH
All the products I have listed above will raise the pH of your soil – you must choose the one which suits your soil’s needs best.
For example, if you have high magnesium content in your soil it is best to choose a calcium carbonate product rather than a magnesium carbonate product. Depending on your initial pH result, you may only need a small adjustment in which case add a little product at a time until you have achieved the correct pH. Good luck.