When trying to grow a lot of food in a small space, every little bit counts. Anything you can do to increase the yields, productivity and health of your plants can make a big difference come harvest time. And if there’s one thing that will keep your soil productive for many years to come, it’s monitoring your soil pH.

The term pH is nearly unavoidable in agriculture, even on small farms. Put simply, it’s a scale by which we measure the alkalinity or acidity of a substance—in our case, soil. Anything under 7.0 on the pH scale is acidic. Anything above 7.0 is alkaline. And 7.0 itself is considered neutral. Although we all know this to be extremely important, do we all know why? As it turns out, there are many good answers to that question.

1. Soil pH Affects Nutrient Uptake

The pH of soil can determine whether or not a plant can access the nutrients it needs. According to the Colorado State University Extension Service:

“In very acid or alkaline soils, some plant nutrients convert to forms that are more difficult for plants to absorb. This can result in nutrient deficiencies. Plants which have evolved under such soil conditions often have developed mechanisms to deal with this issue.”

In essence, without proper pH, your plants may not be able to get the food they need to thrive.

2. Soil pH Affects Microbial Activity

“The soil microbial community is responsible for most nutrient transformation in soil, regenerating minerals that limit plant productivity,” according to a study from the American Society for Microbiology. Lower soil pH tends to favor fungal growth, whereas higher pH tends to favor bacteria, thus the importance of balancing the two becomes an obvious inference: Too low of pH may lead to fungal diseases (described below), and too high may lead to bacterial proliferation. You need fungi and bacteria, but too much of one or the other may lead to issues.

3. Soil pH May Affect Certain Diseases

In a study of soybean diseases performed by the University of Wisconsin, researchers determined that proper soil pH decreased crop damaged by soybean cyst nematodes and brown stem rot. Of course, this idea is likely applicable across crops—that a proper soil pH for the specific crop will help reduce risks of disease by encouraging vigorous plants and not allowing for conditions to become ideal for disease. Note that each crop may have a slightly different pH requirement, but few are extreme, so getting a good balanced pH is the best way to ensure health across the board.

4. Soil pH Affects Crop Yield

Crop yields is a term for how much you get off a single plant—pounds, leaves, fruit, etc.—and this amount is affected by all of the above. If you have poor soil life, yields will suffer. Same goes for rampant disease, nutrient deficiencies and so on. Proper soil pH, which creates a healthy environment in which plants can grow, gives the farmer his or her best shot at high yields.

Measuring Soil pH

There are many home kits you can purchase to test you own soil pH, though it’s recommended that you purchase a soil test from either your local county extension agent or a private tester. A professional test will not only give you an idea of your soil pH and exactly how much of certain amendments you’ll need to apply to find soil balance, but depending on the test, it could provide an idea of what other nutrients or micronutrients your soil is missing. These tests can run anywhere from $5 to $50 per sample. That said, it’s always a worthy investment.

Balancing Soil pH

The two most common soil balancers to increase alkalinity are calcitic lime or dolomitic lime, which has the added bonus of magnesium and calcium. To increase acidity, you’ll need to add elemental sulphur or peat moss. There are other factors that go along with this, however, such as so-called “free lime” in alkaline soils, which may make lowering the pH difficult. Generally speaking, areas with more rainfall have more acidic soils, whereas drier areas tend to have more alkaline soils. But again, a soil test will tell you your pH and how much of what amendment to add—never guess.