“Gardening Soil – Importance of Soil pH”
High quality nutrient rich gardening soil is the most prominent factor for maximum production of vegetables. The importance of soil pH is always the first thing to look at when working with your gardening soil. Without knowing your soils pH you can easily waste hundreds of dollars trying to solve a growth problem.
The Bird Man provides professional soils testing and makes specific recommendations on what amendments to use and when to apply them based off the soil test results. To schedule your Professional Soils Test fill out this form – Contact The Bird Man.
The importance of soil pH is normally overlooked by most gardeners as they struggle to figure out why some or all of their garden vegetables are not growing well. Because these vegetables are not growing well they are more susceptible to insect damage, hence applying unneeded pesticides.
“Why is the Importance of Soil pH the #1 Factor to Amazing Gardens?”
In order to understand why soil pH is so important you have to understand a little chemistry. In order to focus on the importance of soil pH on this link I have created anther link for Properties of Soil which is a very good read to understand the importance of nutrients on gardening soil and plant growth.
If your soils pH is too high or too low one or more of the sixteen essential plant nutrients can’t be absorbed by plant roots. Gardening soil can have ten times the nutrient level needed by plants, but when the pH is not within the optimal range many of these available nutrients can’t be absorbed through the root system. Many of these problems appear to the average gardener that more fertilizer is needed, hence causing even bigger problems.
“Why pH Matters!”
The optimal pH of gardening soil should be between 6.0 and 7.2, but many plants can produce sufficiently in the range of 5.0 – 8.5. What do these numbers mean? pH is expressed as base 10 logarithmic (log) scale. The scale goes from 0 – 10 with zero being pure Hydrochloric Acid and fourteen being Sodium Hydroxide (lye).
Anything (water, soil, coffee, …) with a pH of 7 is considered neutral and everything below 7 is Acidic and above 7 is alkaline. Pure water has a pH of 7 and is considered neutral. Simply speaking there are no units associated to a pH of 0 or 14, just know that a pH below 7 is acidic and above 7 is alkaline.
The optimal range of gardening soil is 6.0 – 7.2 which is a very thin slice of the pH chart above. To put this in perspective, each number is a factor of 10 over the next or previous number. For instance 5 is ten times more acidic than 6 or 4, while 7 is a thousand (10 x 10 x 10) more alkaline than 4.
Gardening soils in areas with high annual average rain fall normally have high acidic soils. Most all alkaline gardening soils are in arid areas that have very low average annual rain fall. Most soils in the state of Georgia have a very low pH while soils in Colorado have a high pH.
Earlier I mentioned that if your pH is out of range then plants have difficulty absorbing nutrients. Take a look at the chart below comparing the gardening soil pH to nutrient absorption. This chart indicates the ability of a plant to absorb nutrients at any level of pH. The thinner the bar the less a plant can actually absorb that nutrient.
Soil pH vs Nutrient Absorption Chart
The red lines intersect the chart through the thickest combined part of the absorption bands. When the gardening soil pH gets lower than 6 potassium, sulfur, calcium and magnesium absorption drops. When the pH gets above 7.2 you can see iron, manganese, and boron absorption drops. Again, the importance of soil pH is critical to the gardening soil for maximum growing results!
Certain vegetables thrive in a gardening soil pH outside the optimal range of 6 – 7.2. Potatoes prefer a soil pH of 5.5 and if you want to grow cranberries they prefer a soil pH of 3.5. Cherries, plums, sage, filberts, and sunflowers prefer a gardening soil pH of 7.0 – 7.5.
What may appear to be blossom-end rot in tomatoes from a deficiency in calcium could be that the pH is too low, hence not allowing the available calcium to be absorbed by the tomato roots. A low gardening soil pH can also cause:
- Stunted growth
- Some plants can suffer with iron and manganese toxicity
- Blighted leaf tips
- Yellowing of foliage
- Poor stem development
- Necrotic or burnt leaf tips
- Cupping & hooking of the leaves
A high pH in gardening soil can exhibit these, and many more, symptoms:
- Overall yellowing of leaves
- Limited root system
- Slow and stunted growth
- Interior leaf veins turn yellow
- Plants look stumpy
- Leave tip dieback in younger leaves
- Leaves may become white
- Leaves may turn red or cherry along their margins
- Older leaves becoming dark green, purplish, or reddish purple
- Sparse looking plants
The importance of soil pH can’t be emphasized strong enough! No one on the planet can look at your gardening soil and tell you what the pH is. Don’t waste your time with the little gardening soil test kits you can buy as they are very inaccurate and unreliable.
“Other Garden Health Check Tools”
None of these tips below are a replacement for knowing the pH of your gardening soil, but rather additional tips every should be doing every year.
- Perform a “Worm Test” – contact The Bird Man for directions
- Creating an Organic Ecosystem