5 Natural Ways To Make Soil More Acidic

Your soil pH should be at the top of the many things to worry about when growing plants. Although many people overlook it, maintaining the correct pH in the system could be the difference between a bountiful harvest and a failed one. Generally, plants prefer slightly acidic soil to alkaline, so changing your soil’s pH usually means you have to make it more acidic.

Here are 5 natural ways to make your soil more acidic:

  1. Avoid using hard or alkaline water.
  2. Use acidic compost.
  3. Consider using compost tea.
  4. Opt for sphagnum peat moss.
  5. Use acidic fertilizer.

Your soil is extremely important to the crops you plan to grow in your setup. As long as you’re not going aquatic, it’s essential to understand how the quality of your soil will affect the plants you grow. This guide will explain all of that and help you solve your soil’s pH problems.

1. Avoid Using Hard or Alkaline Water

Not all water is created equal. The water type you use to water your plants can have far-reaching consequences on their growth.

Among the types of water to avoid is hard water. The term hard water might be strange to some as it’s something most people don’t have to worry about. But if you plan to go far with your crops, you must avoid hard water.

Hard water is water that has taken on calcium and magnesium salts from its surroundings. Usually, these salts are chlorides like magnesium chloride, bicarbonates like magnesium carbonate, or sulfates, as in magnesium sulfate. Of these three, only the bicarbonates are reversible, and even then, it might end up not being worth the effort.

Why Hard Water Can Be A Problem

Hard water is a problem because most of the salts in it will make the soil surrounding your plants more alkaline if used frequently. Raising the pH of your soil this way is very bad for your plants, especially when growing acid-loving plants like blueberries

The best solution to this is to find a way to collect rainwater where possible. Doing this will give you a clean, natural source of slightly acidic to pH-neutral water you can use to your heart’s content. Alternatively, you can also use distilled water if you don’t have rainwater available.

If you don’t have either of these, here are some things you can try at home to soften your water:

  • Use vinegar. It’s a natural way to soften hard water. Simply mixing a cup (237 ml) of white vinegar with a gallon (3.8 L) of water and letting it rest will clear up a significant amount of the calcium deposits. Adding this solution to your soil can help reduce pH.
  • Consider boiling to soften your water. Boiling will cause the minerals dissolved in the water to dissipate.
  • Use a water softener. It works on the principle of ion exchange. The water softener passes the hard water through a resin bed, removing the hard minerals from your water. However, water softeners use sodium, which can be bad for your plants in excess.

2. Use Acidic Compost

Compost is one of the best ways to naturally raise or lower your soil’s pH while also giving it essential nutrients. It’s formed from the decomposition of different types of organic matter over a period. Once this period elapses, you’re left with a crumbly compost similar in texture to the soil. 

Although the nutritional benefits of compost are well documented, its effects on soil pH aren’t often discussed. However, if you add compost to your soil over time, you can regulate soil pH quite well. 

Two things affect your compost’s pH:

  • The content of your compost
  • The composing time

Being able to regulate both properly is key to your soil health.

Add More Green Material to the Compost

All organic matter will eventually decompose over time to give you compost. However, depending on the material type you use, the pH of your resulting compost can be vastly different. 

If you want your compost to be more acidic, you’ll need to add a lot of “green” material. Green refers to compostable material high in nitrogen, like coffee grounds and food scraps. When these materials decompose, they usually lower the pH of the compost.

For acidic compost, you should also use less “brown” material, which has high carbon content as it raises the alkalinity of the compost. Examples of brown materials are sawdust, paper, and tree branches.

Give Your Compost More Time to Decay 

Composting time is the amount of time you leave the matter to decay. Compost goes through a series of changes over time, and once past a certain point, it becomes usable. However, “usable” compost will still change when left alone.

As a result, the “endpoint” for your compost is arbitrary and is determined on a case-by-case basis once you’re satisfied with the result.

Here’s a good rule to follow: younger compost is usually more acidic than older compost.

The changes that organic matter undergoes before its considered compost are brought about by microorganisms and animal activity. As both parties break down the matter, it gradually becomes highly acidic and eventually neutral. 

However, with a high green matter content and enough time, you can use the compost in its acidic state to lower the pH of the soil.

How to Make Acidic Compost

Making compost is an ongoing process rather than a one-time thing. Once you approach it with this idea, it’s easier to maintain your compost pile because it becomes an ongoing habit rather than a task with a clear end.

Follow these steps to make acidic compost:

  1. Get a functional compost bin. I use “functional” here because a compost bin doesn’t have to be specially made. It can be any container large and durable enough to hold the compost you need.
  2. Add your green and brown matter to the bin. The key here is to ensure the matter you use is majorly green. Ideally, compost should contain 30 brown units for every unit of greens. For better chances of getting acidic compost without compromising the quality of the pile, you can reduce the ratio to 20-25:1.
  3. Mix your compost occasionally. Ideally, you should do this every 2–3 days. Mixing is important because it stirs in the microorganisms that decompose the matter and helps the compost mature evenly.
  4. Check the finished compost’s pH. Once the pH is in the acidic range, it’s fine to use. You should use your compost when it’s in the 5–6.5 range on the pH scale. Anything higher on the acidic scale will likely not have much effect on soil pH, and anything lower might be bad for your plants.

3. Consider Using Compost Tea

Compost tea is a form of liquid compost beneficial to plants. Being liquid, it has unique benefits different from its solid form. Unlike solid compost, compost tea is sprayable, allowing you to apply it directly to the leaves of your plants. Also, it loosens up the soil and allows easier nutrient uptake for the plants. 

One key benefit of compost tea comes from its versatility. The preparation time for the tea is short, and as a result, it’s a lot easier to adjust its pH to suit your needs. The preparation is also significantly easier and can be done in a few steps.

Here are the steps for making compost tea:

  1. Gather a handful of compost. It’s important to use compost that is acidic.
  2. Mix the compost into the bucket of water and stir thoroughly. When mixing the compost, add a gallon (3.8 L) of water for every handful of compost you use.
  3. Stir the mixture occasionally. Do the stirring every few hours over two days. During this period, you can add acidic materials like fish hydrolysate or vinegar to reduce the pH of the mixture. Make sure you test with a pH meter periodically.
  4. Separate the liquid from the solid compost after two days. You should be left with a brown liquid, the color of tea (hence the name). This liquid is your compost tea, and you can spray it directly on your plants. 

4. Opt for Sphagnum Peat Moss

Another great way to increase the acid content of your soil is by using sphagnum peat moss. It’s a soil additive formed from the slow decomposition of peat over many years. Peat decomposes slowly due to the phenols in its cells and its wetland habitat. As a result, it can be preserved in its decayed state almost indefinitely. 

This decayed form is great for soil as it promotes drainage and helps in nutrient absorption. Furthermore, peat moss will greatly increase the acidity of your soil, making it a great substitute for regular soil for potted plants. 

However, note that some commercially available peat moss might not be acidic enough to alter the pH of your soil. Always check the pH of the product you purchase from your gardening supply store.

Although useful for gardeners, there are some drawbacks to using peat moss. Peat moss can take centuries to get to a usable point. As a result, it’s not a renewable resource, making it relatively expensive if you plan to use it in bulk.

Another downside to peat moss comes from how it’s mined. The living Sphagnum moss must be scraped off to get to the decomposed peat moss.

This procedure can sometimes cause an imbalance in the ecosystem if it is done excessively, as the top layer that gets scraped off is important to a variety of wildlife. The Royal Horticultural Society has called for a boycott of its use due to these problems and is a strong proponent of “peat-free gardening.”

That said, peat moss does have its benefits, and many agriculturists use it to maximize productivity. To use peat moss to increase soil acidity, simply add 2 inches (5 cm) of peat moss to the top 5 inches (12.7 cm) of your soil and mix it in as well as you can.

5. Use Acidic Fertilizer

Fertilizer is a great addition to soil and works wonders for nutrient growth. However, many fertilizers contain compounds that raise the pH of your soil. If this carries on for too long, your soil can eventually become very alkaline and unsuitable for growing plants.

Consequently, you should limit fertilizer applications if your soil starts to see a significant enough rise in pH level. The optimum pH range for plants is between 6.5 and 7.5. You should correct anything higher than that as soon as possible.

Choose acidic alternatives when it’s time to fertilize your plants. For instance, foliage plants love nitrogen fertilizers during the growing season. In that case, you can choose ammonium sulfate or ammonium nitrate. As they break down, they release nutrients plant roots can absorb while slightly acidifying the soil.

Whenever you use any method or apply soil amendments to alter your soil’s acidity, it’s crucial to monitor the changes by testing your soil regularly.

How to Test Your Soil pH

You should test your soil pH before you decide to alter it. Testing your soil pH will give you a clear picture of where you stand, and from there, you can start to plan out how to get the pH you need.

There are a few methods you can use to test your soil pH, and they’ll be covered here so you can choose which one you prefer.

Use a pH Meter

The first and most common method of testing your soil’s pH is to use the aptly named pH meter. Usually, this comes as part of a larger testing kit and is easier to read as it provides a precise number rather than requiring a reference to compare. 

You could just stick the probe into the soil and take the reading there at face value, but you’ll be much more accurate if you go with the following steps.

Here are the steps involved in using a pH meter:

  1. Dig a small hole about 4–6 in (10–15 cm) deep. It should be the same circumference around, at least. Generally, the circumference doesn’t matter as much as the depth, but there should be enough total volume to hold a cup of water.
  2. Clear the debris at the bottom of the hole. Undoubtedly, there’ll likely be a bit of debris hanging around in the hole. Try and remove as much of it as you can. Depending on your garden’s location, this can be rocks, roots, and sometimes even random trash found underground.
  3. Fill the clear hole with water. Once the hole is cleared of all debris, fill it with some water. Preferably, use rainwater if you can, as it’s more likely to be pH neutral and won’t tamper with the test results. If you don’t have rainwater handy, bottled water is a great alternative as it has a relatively neutral pH.
  4. Stir the water. When the hole is filled, stir the mixture for a few minutes, ensuring the surrounding soil is properly mixed into the water.
  5. Place the probe into the water once everything is mixed. The probe should be in the water for at least a minute or according to the manufacturer’s directions. This step shouldn’t take too long, and once the meter arrives at a final value, you have your results and can act accordingly.

Use a pH Test Strip

A pH meter is usually more accurate, but if you can’t get your hands on one, you can use a pH test strip to get your results. Unlike pH meters, test trips won’t give you an exact number. However, they give you a set of reference colors to match the result you get from your soil sample.

Here are the steps involved in using a pH test strip:

  1. Dig out a few inches of soil. Try to go more than 4 in (10 cm) deep because that’s the soil the roots will likely come in contact with, and it’ll give you a clearer indication of your soil’s pH.
  2. Add a few teaspoons of your soil sample to a container. Take care to ensure that the container you use is clean and dry. If there’s anything left in the glass before you proceed, it can influence your results.
  3. Separate the debris. Try to get out as much of the debris in the soil sample as you can. Here, you can use a sieve to separate the larger chunks from the soil if you have a fine enough mesh. Try to sift the leftover soil through your fingers, bit by bit, to ensure that it’s as debris-free as possible.
  4. Add distilled water to the soil. If you have rainwater handy, then it’s a good, cheap option, but you can use bottled water as an alternative. Once you have the water in, stir vigorously and leave it standing for at least half an hour.
  5. Filter the water to get the filtrate. You can use a coffee filter. Alternatively, you can get filter paper. Use the filter paper to pass the liquid slurry through it and allow it to filter through. You should get a clear liquid after a while, but if you don’t, repeat the process.
  6. Add your pH strip to the filtrate. The time you might have to leave it in could vary, so it’s best to follow the manufacturer’s instructions here.
  7. Compare your results once the color change on the strip is satisfactory. Remove the strip and compare it to the provided reference sheet in your pack to determine the pH of the soil sample.

Try Homemade Alternatives

You’re still not out of luck if you don’t have access to either a ph meter or a home testing kit. A lesser-known fact is that you can test your soil with vinegar and baking soda, although it’s significantly less accurate. This test will give you a general idea of the type of soil you have rather than a precise figure or range.

Here are the steps on how to test your soil with vinegar and baking soda:

  1. Follow steps 1 to 4 above.
  2. Mix some vinegar into the water/soil mixture. Half a cup (118.3 ml) of vinegar to about a cup of soil should do the trick. The vinegar will react with the mixture and bubble if your soil is alkaline. 
  3. Mix half a cup (118.3 ml) of baking soda with a separate soil and water sample if you don’t get a reaction with vinegar. If the soil is acidic, you’ll get a reaction as the baking soda starts to react.

If you don’t get a reaction with either method, that means your soil is neutral. 

Although these methods have varying degrees of accuracy, with a pH meter being the most accurate, they’re still not enough if you need an exact value. The only way to get an exact pH value is to send some soil samples to the lab for analysis. 

The good thing is that you’ll rarely ever need to be that accurate. You should do this test around the fall, right before you plant new crops. You have an exact pH value during this time and can adjust your plans accordingly to alter the pH to an acceptable level before planting begins.

Why It’s Important to Regulate Soil pH

The pH of your soil is extremely important. It affects various things and ensures that your plants will grow optimally, provided that other conditions like proper lighting and soil nutrients are also met.

pH is the hydrogen or hydroxyl ion content of a sample. These hydrogen and hydroxyl chemical groups give acidic and basic characteristics, respectively. As a result, the pH value measures the acidity or basicity of a sample.

Regulating pH values is very important in all forms of agriculture. One of the most common reasons for yellowed leaves on plants is improper soil pH. Soil pH influences the number of nutrients in the soil and how well they’re absorbed. As a result, the wrong pH in your soil will leave your plants malnourished.

Further, microbial presence in the soil also directly correlates to the pH level. Microbes like bacteria and fungi create symbiotic associations with plant roots and increase adsorption rates. However, outside of the suitable pH, these microbes won’t thrive, and consequently, the plant roots, and by extension, the plant itself, won’t get the nutrients it needs.

Most of the time, it’s a good bet to assume that your soil is neutral. Most plants seem to grow just fine in neutral soil, so you might be wondering why it’s necessary to acidify your soil at all. 

Your soil should be acidic to promote plant growth. Although most plants do fine in neutral soil, they do even better in slightly acidic (6.5 pH) soil where nutrients are more readily accessible to plant roots. Some plants like blueberries and rhododendrons even prefer pH levels of around 5.0, which can be hard to obtain and maintain if your soil is inherently alkaline.

If you’d like to give your plants the optimal conditions for growth, then putting them in soil with a slightly acidic pH is a good choice. Acidic soil conditions are far more important than just the pH value as the right pH level promotes the growth of plants and microbes and increases nutrient availability in the soil.

Alexander Picot

Alexander Picot is the founder of TheGrowingLeaf.com and its lead content writer. He created the website in 2022 as a resource for horticulture lovers and beginners alike, compiling all the gardening tips he discovered over the years. Alex has a passion for caring for plants, turning backyards into feel-good places, and sharing his knowledge with the rest of the world.

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