To understand Soil pH and its Effects on Plant Growth let’s first understand what soil pH , ways to measure and preserve it is. In simple terms, soil pH means the measure of sourness (acidity) or sweetness (alkalinity) of the soil. It is measured on the scale of 0.0 to 14.0. The highly acidic soil is 0.0, and highly alkaline soil is 14.0. If the soil measure 7.0 its is neutral, i.e., it is neither acidic nor alkaline. When the soil’s pH value decreases from 7.0 to 0.0, it gets more acidic, and if the value increases from 7.0 to 14.0, it gets more alkaline.
How does soil pH affect plant growth?
Bacteria that are responsible for releasing nitrogen from the organic matter and some fertilisers operate ideally if soil with pH value ranging from 5.5 to 7.0.
Plant nutrients leach quickly from the soil if the pH value goes below 5.5 than from soils within the range of 5.5 to 7.0.
In some soils, aluminum can be dissolved if the pH level is below 5.0 and becomes toxic to plant growth.
Soil pH may affect the plant nutrients too. Nutrients are readily available to the plants if the soil ranges from 5.5 to 7.0.
Soil pH can also affect the structure of the clay soil. In the optimum range, clay soils are granular and easy to work with. But, if the soil is extremely acid or alkaline clay, the soil tends to become very sticky and makes it hard to cultivate.
How to measure soil pH?
To measure the soil pH, you could pick up inexpensive soil test kit, digital soil ph meter or a pH tester from the local nursery. The soil test kits are readily available and consist of a test tube, testing solution and a colour chart. All you have to do is - put your soil sample in the test tube, add recommended amount of solution, shake it and leave it for about an hour to settle. Once the solution changes the color, you could match the hue to the colour chart and determine the pH value of the soil. Depending on the result the further course of action could be decided. Read about ways to prepare healthy garden soil.
How to adjust the soil pH value?
Now that you have tested your soil, it's time to set the pH value. Result: If the soil pH value is less than seven then (acidic)
Add organic matter in the form of a well balanced, neutral compost. Note that adding humus is an ideal and efficient way of changing pH
Add agricultural lime. Apply 100g to each meter squared. Remember that lime can only be accurately used if a complete and through the mineral test is performed. This process will slowly increase the pH value of your soil (6 months). But be very careful and do not over apply.
Result: If the soil pH value is greater than seven then (alkaline) Keep in mind that the soil with this pH value will be harder to rebalance
Add green manure crops into rotation more frequently
Add organic matter in the form of a well balanced, neutral compost. Note that adding humus is an ideal and practical way of changing pH
Use powdered sulphur in an extreme condition. Note that sulphur is antimicrobial i.e. it will kill the beneficial microbes in your soil if applied regularly. The most efficient way is to use a handful per square metre, that too once a year. It will take about six months to show significant results.
Balancing the soil’s pH is indeed a shortcut to growing healthy food. Once you work on this, it is pretty easy to treat the mineral deficiencies in the plants.
Books for learning more about garden soil health in depth:
Marathi book - Sashvat shetisathi sendriya khate. Fun Fact: Dr Soren Sorensen - The inventor of the pH scale developed it in 1909 to determine the acid content of his beer!
