What is soil pH, and why is it important for my garden?
The acidity or alkalinity of your soil is measured by pH, which stands for potential Hydrogen ions.
pH is measured on a scale from 1 to 14:
pH of 7 exactly: neutral (neither acidic nor alkaline)
pH less than 7: acidic soil
pH greater than 7: alkaline soil.
Alkaline soil is known as “sweet” and acidic is known as “sour.” In humid climates, soil tends to be acidic, and in dry climates it tends to be alkaline.
How soil pH affects plants
Soil pH affects the availability of nutrients in the soil to plants, and a proper pH level helps prevent soil borne diseases.
Vegetable plant pH preferences
Most plants prefer a value of around 6.8, but will grow just fine with a pH in the range of 6.4 to 7.5. If you want to fine tune your garden soil, be aware that different types of plants have different preferences for soil pH, which you can research through a quick online search. Sweet potatoes, for example, prefer more acidic soil (5.5 – 6.0). Tomatoes, however, prefer more acidic to neutral soil (5.5 – 7.5) and asparagus prefers more neutral to alkaline soil (6.0 – 8.0). Acid loving plants like rhododendrons like a pH of 4.5 to 6.0. So you can see that you might want to have an idea of pH requirements for plants when planning your garden.
Testing your soil pH
Check your soil pH regularly, at least twice per year. It’s easy to find out the pH of your soil using a kit available at most garden stores, hardware stores, and online. A good garden center will most likely test a soil sample for you.
Test kits normally contain a test tube, solution, and a color chart. You place your soil in the tube, add a few drops of solution, shake up the tube, and let it settle for about an hour. Then match the color of the tube’s contents to the chart.
A creative way to test your soil pH is to plant a hydrangea. If your soil is acidic, the blooms will be blue. If the soil is alkaline, on the other hand, the blooms will be pink.
Adjusting your soil pH
It’s generally easier to make your soil more alkaline than it is to make it more acidic. To make your soil more alkaline by increasing the pH, add agricultural lime (a form of calcium) to your soil, less for sandy soils and more for clay and peaty soils. Bone meal, ground limestone, chalk, and crushed marble all contain significant amounts of lime.
Making your soil more acidic by lowering the pH takes time and is best done over a growing season, or even several seasons. You may want to consider building a raised garden bed and filling it with neutral soil. A thriving population of microorganisms tends to help soil be slightly acidic. So adding Great Big Plants Natural Compost Extract will provide a base of beneficial microorganisms and supply a food source for them.
If your soil is already slightly acidic but you want to increase the acidity, add peat, iron sulfate or even coffee grounds to it. For a more dramatic increase in acidity, use ground rock sulfur mixed thoroughly with the soil before planting. To ensure the effectiveness of the sulfur in the root zone, the most crucial area affected by pH, apply Great Big Plants Natural Compost Extract along with this mixture. The beneficial microbes contained in Great Big Plants react with the bacteria in the sulfur to create minor amounts of sulfuric acid. It is possible that you have enough sulfur in your soil already, but have a sub-optimal microbe population. Additions of Great Big Plants should help remedy this condition as well as provide other benefits.
Maintaining the pH balance
Adjusting soil pH is not a one-time task, but rather a regular process. Over time, nutrients and other constituents will be leached from the soil, and the pH will shift back to what is was before adding amendments. Keeping tabs on it and managing pH will encourage your plants to grow efficiently and beautifully.