Why Does Your Soil pH Keep Dropping?

As a gardener, you probably already know how vital soil pH is. Occasionally, checking it can give you some inside knowledge about how your plants are absorbing and feeding on the soil it’s planted in. If you’ve noticed a steady decline, you may be wondering why the drop keeps happening.

Soil pH can drop if you lose organic matter in your garden, have an eroded or compact top layer, have issues with irrigation or rainfall, or use nitrogen or sulfur fertilizers for a long time. pH is also dependent on the soils in your garden, and some soils are naturally more acidic than others. 

Below, we will discuss some of the common causes of soil pH dropping and give a few strategies to raise the pH back up. Additionally, we will discuss the importance of tracking your soil pH and keeping it at a stable level. 

Reasons Why Your Soil pH Drops 

Whether you’ve already done some testing or you just have some suspicions, it can be challenging to figure out why your soil’s pH is dropping. 

A few things can indicate soil pH drops, and tests that keep coming back lower and lower can be frustrating. Is it something you’re doing or a natural occurrence for soil pH to drop? 

Here are some reasons why your soil pH may drop:

  • Extended nitrogen or sulfur fertilization
  • Rainfall
  • Irrigation
  • Loss of organic matter
  • Problems with the top layer of the soil
  • The soil you are using is naturally more acidic and significantly reduces the soil pH when blended with other soils. 
  • Harvesting high-yielding crops

Low pH can be caused by any number of things or a combination of a few. Usually, if your soil pH is pretty low upon receiving it, you might be able to determine right off the bat that your parent soil is high in acidity. 

Otherwise, it might take a little more troubleshooting. You can use the process of elimination, slightly change your gardening routine, or try some DIY solutions to figure out what’s been making your soil so low in pH.

Let’s look further into how the reasons mentioned above can lower your soil pH:

Extended Nitrogen or Sulfur Fertilization 

Nitrogen or sulfur fertilization may be making your soil low in pH if you’ve been doing it for an extended period. Typically, for soils too alkaline or low in organic material, experts advise gardeners to fertilize with nitrogen or sulfur. 

This method will make these two nutrients readily available and lower the pH of the soil. However, it can lower your pH too much over long periods and make your soil too acidic for your plants.

Rainfall & Irrigation 

Sometimes, rain can affect the pH level of your soil. In general, soils that have experienced more rainfall or are in more humid places can become more acidic than those that are dry. 

It isn’t necessarily because of “acid rain”, a phenomenon where rain falling from the sky has a low pH, though acid rain is a leading cause behind the theories of why soil has become more acidic over the years.

By the logic that rainwater or rainfall is affecting your soil, you’ll want to be sure to have a proper drainage system in place. Long-term exposure to too much moisture, humidity, or rainfall might cause your pH to drop, so making sure to get excess water out of your garden is critical. 

Setting up an irrigation or drainage system will also prevent compact soil and soil that doesn’t seem to be absorbing moisture

Loss of Organic Matter

Organic matter has a great deal to do with the health of your soil, and its effect on pH is also an essential concept to understand. Not only does organic matter have a direct effect on the amount of pH in soil, but it can also support soil in reaching a stabilized pH so that your plants are not constantly going back and forth between acidic and alkaline levels. 

If you’ve faced the loss of organic material in your soil, this can be fixed by composting or mulching. Both will add organic content to your garden and help raise and stabilize your garden’s pH. 

Harvesting Crops

Harvesting crops affects the soil because nutrients are no longer getting to the soil or being taken from the soil in the way they were before. 

Additionally, problems with the top layer of your soil, such as compaction or erosion, are troubles within themselves beyond the outlasting effects on soil pH. 

Signs of Low pH in Soil 

So how will you know if your plant is low in pH? If you’re reading this article, chances are you’ve already tested your pH and are looking for solutions. If not, there are a few indicators for low pH. 

Your plants may give you a sign that their pH is low if they:

  • are dying with seemingly no cause
  • seem as if they are suffering from deficiency in nitrogen or other nutrients affected by low pH
  • facing some kind of discoloration
  • aren’t growing as rapidly as before

You may also notice a pH problem if repotting the plant (but keeping the same soil) hasn’t fixed the issue

Measuring Your Soil pH 

If you’re suspicious your pH is low and want to be sure, you can test your soil pH in a few different ways. 

Laboratory Testing

First and foremost, if you have the resources and budget available, you can send a sample of your soil into a lab. Not only will this give you information on your soil’s pH, but it’ll give you insight into nutrient deficiencies and other exciting things about your soil. 

If soil pH doesn’t end up being your problem, having the results at your disposal may help you further troubleshoot.

pH Meter

You don’t have to send soil into a lab to figure out what’s going on, though. Many moisture meters have a pH setting that moves based on the acidity in your soil. 

If you don’t have a moisture meter, you can purchase a three or five-setting one that determines your house plants’ pH, moisture level, light level, temperature, and humidity or smaller outdoor plants. All you have to do is stick the two metal rods into the soil, avoiding any roots, and read out the results.

pH Testing Kit

Additionally, you can find a testing kit for just about any budget. Some are similar to the acid testing kits you may have used in high school or college science classes, while others are made specifically for soil and soil samples. 

Usually, you’ll test a strip or add a test sample to a container, which will read back results to you. 

How Can I Raise My Soil pH?

If you’ve determined the cause of your soil pH getting lower, you may now be wondering how to raise it back up. Soil pH can determine how many nutrients are available to your plants, and something too low might deprive them of the vitamins they need to grow. To raise your soil pH, you have a few options. 

You can raise your soil pH to a less acidic level by composting, liming, or mulching. Mulching and composting will help organic matter infiltrate your soil and prevent pH drops. On the other hand, liming is utilized by farmers and gardeners alike to make the soil more alkaline. 

Though none of these are quick fixes, investing in one of these solutions will change your pH in the direction you want. Just be cautious not to use too many strategies or any excessive combination of all three. 

Doing too much can increase your pH to a level that makes the alkalinity of the soil a problem instead. Soils must stay right around the 6.0-7.0 range, almost neutral but a little acidic. Otherwise, plants do not have access to all the nutrients present in the soil. 

The Importance of Soil pH 

Soil pH is the measure of how acidic or alkaline your soil is. On the pH scale, 7.0 is neutral, with everything below being acidic and everything above being alkaline. 

In our real life, acidic things include citruses like oranges and vinegar, while something alkaline might be milk or your antacid (hence why they help you when you overeat or have a sour stomach).

Only certain nutrients are available at any given pH level. For this reason, soil pH can indicate how many nutrients are readily available to your plants. Even if your soil is rich in vitamins and minerals, your plants can’t utilize them if the pH is too high or too low. 

In the garden, acidic soil isn’t necessarily harmful or bad for plants as long as it’s kept above a 6.0 on the scale. 

Even then, some vegetables and fruits (namely blueberries) like even more acidic soils. Alkaline soil can also be harmful because it means your plants are missing out on some nutrients that are only available in more neutral soil. 

Nutrient deficiencies in your plants can inhibit health or stop plants from growing to their full potential. The soil pH can determine the yield of a crop or give you indicators as to why a crop isn’t blooming as usual, so farmers are constantly testing for their soil pH. 


If you’ve noticed your soil pH dropping, you’re at least one step ahead of the gardeners who don’t know how vital soil pH is. It can affect your plant’s growth and hinder it from thriving if not properly dealt with. 

Typically, if your soil becomes acidic, it has something to do with the parent soil, overharvesting of materials, organic material decaying, over-fertilization, or rainfall. You can lime, compost, or mulch to help raise your soil pH and ensure your plants get all the nutrients they need.

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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