If you’ve been gardening for a while, then soil pH will most likely not be a new concept to you. If you’re completely new to gardening, a basic understanding (at the very least) of how pH chemistry works is important for the best farming and gardening practices.
Soil pH indicates the acidity or alkalinity of your soil. Working with soil that is either too acidic or alkaline for the nature of your plants would largely affect germination and ultimately reduce yield.
Soil pH is a useful property to measure in garden soil because it influences several soil factors key to improving plant growth and long-term health. pH is an acronym for Potential Hydrogen, a property represented on a scale of 0 to 14 which measures the amount to hydrogen and hydroxide ions present in a substance – which in this case, is your soil.
Why is it important to know your soil’s pH?
While you don’t have to know everything about the complexities of pH chemistry, a substantial amount of knowledge is required to get you through your farming needs. Essentially, the amount of hydrogen in the soil indicates how acidic it is, which affects a host of plant health factors as a function of plant type.
Acidity is an important property to take note of in any plant because it determine a host of factors such as plant health, ripeness for harvest, and variety difference.
The most essential use of hydrogen to soil content is its role in nutrient uptake. It also plays major roles in several other soil processes such as microbial activity useful for breaking down material to create nutrients.
This article aims to provide you with solid information on how to get the best out of your soils by testing for pH and knowing what affects pH levels in soils.
Quick breakdown of the universal pH scale
The pH scale is a standard model all over the world, running from 0 to 14, with 0 being the most acidic and 14 the most alkaline. A neutral substance will have a pH of approximately 7, e.g water. Most soils are within a pH range of 4.5 to 8.5. Too much or too little hydrogen in the soil will adversely affect plant growth and health, and every plant has its own required pH range, although a neutral of 7 is the most desired.
Altering the pH of a soil can be done either by mixing it with another material of a varying pH to even things out or adding chemicals to increase hydrogen or hydroxide ion supply.
Testing soil pH with strips
One of the quickest and most reliable methods of testing pH is by the use of litmus paper, a pH indicator made from dye-treated filter paper which changes colors (mostly red or blue in accordance with the acidity levels of a substance).
- Mix a handful of soil with distilled water at room temperature. Distilled water is the best choice to prevent impurities in tap or rain water from altering the results. Collect soil from various points in the garden to ensure that you obtain an absolute result representing the entire area. Mix the soil and distilled water in a bowl to form a homogenous and reasonably combined slurry or paste.
- Insert the pH strip into the middle of the mixture and hold the strip steadily for 20 to 30 seconds. Ensure to read the instructions on the strip packaging as some manufacturing companies may require you to hold it for a longer time.
- Remove the strip from the mixture and immediately dip into another bowl containing distilled water to wash off soil paste. The portion of the strip dipped into the paste is likely to have changed color in accordance with the color code of the strip (usually written on the packaging).
- The color code is the key to obtaining the pH of your soil. Compare the color on the strop to any provided code and know you soil pH.
Testing soil pH without strips
It’s important to note that outside the litmus test, all other pH tests are less reliable and usually error-ridden. However, they are an interesting way of exploring pH and make a fun experiment for children as well as being a useful tool for the serious gardener.
Vinegar and baking soda
- Collect soil in a cup or bowl from every point in your garden and pour two spoonful’s each in two separate bowls. In one bowl, pour half a cup of vinegar and observe the reaction. If it foams or froths, the soil pH is probably about 7 or 8, indicating a slightly alkaline nature
- If there is no reaction upon addition of the vinegar, add enough distilled water to the other bowl to make a muddy mixture. Add half a cup of bicarbonate of soda (baking soda) and mix thoroughly. If it foams or froths, the pH of the soil is somewhere between 6 or 7, indicating a slightly acidic nature.
- If there is still no reaction, the soil can be deemed pH neutral and perhaps the result most gardeners and growers are looking for.
The cabbage test
- Red cabbage can be used to test for pH. Simmer a cup of roughly chopped red cabbage in a saucepan with two cups of distilled water for about five minutes. Drain the water and allow it to sit for 30 minutes. If the liquid turns blue purple, it most likely has a pH of 7.
- After the liquid has been allowed to settle, pour a couple of inches of the liquid into a jar and add two spoons of soil from the garden, allow it to sit for another 30 minutes.
- If it turns a reddish-pink shade, the soil is acidic while a blue-green color indicates alkalinity. No color change means the soil is neutral.
Adjusting the pH of your soil
Plants require specific pH levels to thrive and flourish to their fullest potential. For most gardeners, a neutral soil pH is the best bet, but for some plants, they might require a bit more acidity or alkalinity.
Several home-made and store-bought materials can be added to the soil to effect this chance.
Increasing your soil pH
For an undesirably acidic soil, the pH would have to be increased to 7 or above. This is best done by the addition of agricultural lime which is juiced and sprinkled on the soil. This should be done gradually and soil pH re-tested between two and three-months post-mixing. Soil pH can also be increased using ground up animal bones, the shells of any egg or seafood and also ashes recovered from the burning of hardwoods.
This is best done in the fall to enable the amendments begin decomposition and act upon the soil. If you choose to do it during the spring, it’ll have to be done several weeks before planting.
Achieving the pH best-suited to a given plant does not need to be completed in a single year; as a general guideline, pH change should be kept within a limit of about 0.5-1.0 each year, with the soil being re-tested roughly every six months.
Lowering your soil pH
To lower the pH of a soil from a high alkaline level to a neutral or acidic level is best done with sulfur. Sulfur is readily available in gardening stores and is an effective chemical in increasing hydrogen levels.
Alternatively, a range of waste materials from the home and garden can be put to use to reduce pH including leaf mulch, sawdust from pine, manure or even coffee grinds.
As with the mixing of amendments to increase soil pH, materials for lowering pH should be added gradually and the soil re-tested within the next three months. In dry environments, high pH could also be a result of mineral salts accumulating in top soil. If this is suspected, the soil can be regularly rinsed with normal tap water to flush the minerals to the subsoil below the plant or crop’s root zone.
How to determine soil texture
Soil texture is another important property to note about your chosen soil type. It refers to the mixture and content of particles such as sand, silt and clay. It also determines the relative ease at which the soil can be worked. Some plants require soils with a specific texture for maximum yield.
- Clay soils are those containing high levels of alumina-silicates which generally provide higher nutrient levels but poor drainage, and are referred to as fine-textured soils.
- Sandy soils, on the other hand, provide good drainage but tend to be lower in nutrients and are known as coarse-textured soils.
- A soil containing components of both clay and sand is referred to as a loam and is the type of soil desirable for growing most plants.
Factors that affect soil texture include:
- The type of parent material or rock which produces the mineral part of a soil. The two main rock types, igneous and sedimentary determine the soil category with igneous resulting in sandy soil and sedimentary in clay.
- Climate and the type of vegetation in the local area, with climate determining the extent and rate of rock weathering, and local vegetation determining the amount of organic matter gathering on the ground.
To check for soil texture, simply pick up and squeeze a handful of soil. If, when squeezed and then gently poked with a finger, the soil retains its shape, it is clay. Soil that crumbles immediately after squeezing is predominantly sand. A soil that retains its shape when squeezed but then crumbles when poked is a loam which is the best type of soil.
Your gardening affairs would run much smoother if you have a solid idea of your soil’s pH. It influences some of the most important plant-soil processes, such as nutrient uptake and activity of microbes which break down organic matter and convert it into available nutrients.
Of the two types of pH tests, it’s best to use the litmus paper only or a combination of the two to get repeatable and accurate results of you soil’s pH.
Most gardeners prefer a soil pH of 7, neutral, but not all plants would fare well in this condition. However, soil pH can always be altered or adjusted using the above-mentioned home-made or store-bought materials.
Happy gardening people!