If we talk about the ideal pH for plants then it would be a little difficult to generalize as different plants have different requirements. But most of the plants growing in our backyards and in our houses are more or less of the same nature. Their nutritional requirements, water requirements and pH level requirements are almost same. The ideal pH for houseplants is between 5.5 to 7. If we want to talk about more accurate values then a pH of 6.5 is best suited for them.
Maintaining a proper pH is very important as it determines the nutrients which can be absorbed by the plants. If the plants are too sensitive, improper pH can lead to severe deficiencies and death of plants.
Usually plants require pH which is slightly acidic. Some house plants like ferns require a slightly basic pH which is between 6 – 8. Most of the vegetables, except for asparagus also require pH between 5.5 to 7. And what about our beautiful flowering plants? Well, they also require a slightly acidic pH with a few exceptions like geranium, begonia and day lily which require slightly basic pH. Some fruit trees like apple and blueberry require pH between 4-6 which is medium acidic. Rest of the common fruits like orange, strawberry, grapes etc. thrive well between 6-7.
What happens when we add fertilizers to the soil?
Addition of any kind of chemical may cause a shift in soil’s pH. The most common supplements that we give to our plants consist of NPK. Nitrogen can be given in the form of nitrate or ammonia. Addition of ammonia can lead to a decrease in soil pH making it more acidic while nitrate based fertilizers like sodium nitrate hardly cause any noticeable change in soil’s pH.
Phosphorus and potassium fertilizers cause a very slight change in pH of soil. So they are nothing to be concerned about. Phosphoric acid fertilizer can lead to change in soil pH levels towards acidic.
Micronutrients like manganese, zinc, iron etc. are required in very small quantities and cannot cause any significant change in soil pH.
If you are concerned about the soil being too acidic and can harm your plants, there is a very simple solution to it. Add a little bit of lime (Calcium Carbonate) to the soil which acts as an amendment. This will increase the pH levels and save your plants from any further damage.
First of all let us understand what exactly pH is?
In a simple non scientific language, pH is the value which indicates whether a solution or a substrate (i.e. soil) is acidic, basic or neutral. But even this little information can help us manage our plants more efficiently.
How can we measure the pH value?
There are various methods to determine pH levels. Some are complicated and require sophisticated lab equipment while some work with just a little piece of paper. Here is a list of methods for you –
Using vinegar and baking soda – This can be a DIY kit for you to measure or at least have an idea about the pH level of the soil. Dig up soil from a few inches below the top layer and clean it. Remove pebbles or dried up leaves and dissolve the soil in clean water to make it into a solution. Pour the solution in two separate bowls and add vinegar in one and baking soda in another. If the soil is acidic it will form bubbles or fizzes in the bowl containing baking soda while a basic soil will fizz when mixed with vinegar. This will not give you an accurate measurement but will indicate the direction of your soil’s pH.
Litmus paper – It is a small strip of paper which comes in either blue or red colour. All you need to do is place a small drop of solution on it and wait for a few moments. After some time the red coloured paper will turn blue indicating that the sample is alkaline or basic. If the paper doesn’t changes colour, that indicates acidic solution. An interesting fact to know here is that this paper is derived from organisms known as lichens which change colour after coming in contact with acid or base. A colour indicator strip is also available along with litmus paper. This will help in determining the various ranges of red and blue colour which will give us a more appropriate value of pH.
pH meter – This instrument uses aqueous solution of soil to measure pH. All you need to do is to dissolve some amount of soil in clear water and measure the pH using pH meter. It will give an accurate value without much hassle.
The optimum value of pH for plants is between 5.5 – 7. Addition of fertilizers or even watering the plants can sometimes disturb the pH level of the soil. Hence it becomes important for us to know whether our plants are in some kind of distress or not. Try and measure the pH in 6-8 weeks or after addition of any fertilizers to maintain healthy plants.