How to Adjust Soil pH for Vegetable Gardens
Soil pH for Vegetables
If you slept through high school chemistry class, never fear - you can still learn the basics of soil pH for vegetables to ensure a great garden this year. pH refers to the scale of acid to alkaline, a scale developed in the early 20th century by chemists trying to describe the range of pure acid (0) to pure alkaline (14) of chemistry in the world. The pH scale runs from 0 to 14, with 7 being at the very center. Most vegetables thrive in a slightly acidic environment, and indeed most plants need a soil pH of 5.5 to around 7.0. That range is variable and flexible, however, and depends greatly on the type of vegetables you're trying to grow in the backyard garden, or in the case of blueberries, fruit. Some plants such as the aforementioned blueberry need a highly acidic soil. Few need a deeply alkaline soil.
So given that you just want to grow a few tomatoes or some lettuce, what do you really need to know about the acid and alkaline base? What do you need to know about soil pH for vegetables? I'll give you the basics of soil PH, pH testing for soil, and other ways to analyze your soil below, along with some simple ways of adjusting the soil pH if you have to do so.
Note that I say "if you have to do so." You shouldn't try to drastically change your soil pH without first consulting someone from your local County Cooperative Extension Office or another expert. Once you drastically alter your soil pH, it can be difficult to get change it back. It can get costly and time consuming. Be certain of your soil pH before adding anything to change it, and have your soil tested and analyzed by a professional laboratory before adding vast quantities of additives. Most of the time, you can and should adjust soil pH gradually and slowly using natural additives such as compost and peat moss. You really can't go wrong adding compost to the soil.
How to Test Soil pH
You can have your soil analyzed professionally at a laboratory, take a sample to a garden center or another location that tests soil, or purchase a test kit and test it at home. All three methods have pros and cons, and all three will yield a basic soil pH reading that will help you understand your soil's chemistry and potential additives it needs. If you have your soil professionally tested through an independent laboratory or a garden center, they should be able to analyze other aspects of soil compositions such as particle size and organic material. These three points of information - pH, particle size (which tells you your soil type) and organic matter - can help you better understand what your vegetable garden needs in order to grow more abundant, tastier vegetables.
How to Test Soil pH: Soil Collection Basics
No matter which route you pursue, the basics of collecting soil are the same.
- Use a plastic bag or a plastic or glass container to transport soil samples. Don't use a metal container, as metal has the potential to contaminate the readings.
- Scoop approximately 1/2 cup of soil from several locations around the potential garden area into each soil container. Keep them separate from one another, and mark or label the container with the location and date of sample collection. Dig down a few inches but not too far for the samples. Don't take it right off the top.
Taking several samples yields a more accurate test result than a single sample. For example, my garden on Long Island had odd stripes of clay alternating with sand. If I had just taken a soil sample to the lab from the clay area, the result would be different than if I had taken a sample from the sandy area.
If you're taking soil samples at home, follow the pH test kit instructions to test your soil. Once you know the results, write it down in your garden journal or somewhere you can keep track of it.
Those taking soil samples at home may also want to consider conducting an at-home test to determine how much organic material is in the soil. You want plenty of organic material in the soil; it feeds the soil colonies of bacteria, microbes, worms and insects that make for happy plants. Here's how to determine the type of soil you have (clay, loam, sand) and how much organic material is in the soil.
What’s My Type? Do-It-Yourself Soil Test
- Clean glass jar, such as a clean and dry mayonnaise or pickle jar
- Soil from your yard
Fill the jar about 2/3 full with water. Now fill the jar with soil, leaving about 1” from the top free of water and soil. Put the lid of the jar on very tightly. Shake the jar back and forth vigorously for about a minute. Now put the jar down on the countertop. Let the soil settle. After a minute, put a mark on the jar next to the first layer that settles out. This tells you about how much sand you have in your soil sample. Allow the jar to sit for an hour, and place another mark on the next layer. That’s your silt later, and shows you how much silt is in your soil. Allow the jar to sit for a full 24 hours, and place your last mark on the top layer. That’s the amount of clay in your soil.
Depending on the amount of each element – clay, silt or sand – you’ll know what you are dealing with. No matter what type of soil you have, adding organic material can improve it.
Adjusting Soil pH
Soils generally fall into the acidic range or the alkaline range. Most garden vegetables thrive with a soil pH of around 6.5 or so, but know your veggies - check on individual vegetables if you're not sure what each one needs.
Acidic soils have a pH around 5.0 to 6.0. Garden lime adjusts the soil pH gently for acidic soils. Follow the package directions and add lime according to the amounts per square foot as indicated on the package. Acidic soils are actually fairly common in the United States.
Alkaline soils soil types generally register a pH of 7.0 to 8.0. Powdered sulfur is used to lower soil pH in alkaline soils. As with adding lime, read and follow the package directions for the amount of sulfur to add and frequency of application.
All Soils Benefit from Compost
It doesn't matter what your soil pH reading is...all soils benefits from compost. Compost is nature's ultimate soil booster. You can compost banana peels, coffee grinds, eggshells, fruit and vegetable peels, leaves and grass clippings. You don't even need a fancy compost tumbler or bin. I've made compost bins from stacks of bricks and blocks, an old dresser drawer on the ground, and a garbage can with holes cut in the side for ventilation. The point of composting is to allow nature to break down the organic materials into the elements that feed the soil and in turn, feed your plants. A good well-rotted animal manure such as cow manure, horse manure or chicken manure also boosts soil fertility. Just don't compost meat, bones or similar items; they attract vermin.
Test Soil Frequently
After testing your soil, adding compost and planting a garden, it's a good idea to test soil annually or at least every two years. Soil pH can change over time. It's important to work slowly with soil, too, and never dump a lot of amendments on it at once. The only exception to that suggestion is compost. You really can't go wrong adding plenty of good old fashioned compost to the soil. Test your soil each spring before planting, add amendments as recommended, and record the results. Over time, your garden will reward you with abundance.
More Information on Soil Testing and Soil pH
- Soil pH
NASA's explanation of soil pH. It's written for kids, but worth a read.
- SUNY-ESF E-Center: Soil pH: What it Means
SUNY-ESF is the oldest and most distinguished institution in the United States that focuses on the study of the environment.
- Soil Types and Testing
- Welcome to Texas A&M University Soil, Water and Forage Testing Laboratory
Texas A&M University Soil, Water and Forage Testing Laboratory
- Soil Testing
NCDA Soil Fertility Note 1. An explanation of the importance of testing soil for pH and nutrient content
© 2011 Jeanne Grunert