The Pro Farmer

Ph measurement of soil

PH is a measure of how acidic/basic water or soil are.

The range of pH extends from zero to 14.

A pH value of 7 is neutral, because pure water has a pH value of exactly 7.

Values lower than 7 are acidic, values greater than 7 are basic or alkaline.

The pH level determines the availability of the essential elements to plants.

PH level has an effect on mineral absorption.

For example, nitrogen (N), phosphorus(P) and potassium(K), calcium (Ca) and more, are optimally absorbed when the level of acidity in the soil ranges from: 6.5-7.5.

The level of acidity in the growing medium directly affects the ability of the roots to absorb nutrients.

Each nutrient has a range of acidity where the absorption to the plant is maximum but there is a range of acidity level where all the essential ingredients for the plant can be absorbed.

This range varies slightly from soil substrate to other hydroponic substrates but in principle can be used for all crop forms.

An acidity level which is too high or too low will impair the plant’s ability to absorb the minerals and fertilizers given in irrigation.

The benefits of PH balance in irrigation water are:

Faster growth rate results in larger plants.

Balancing acidity around the roots will allow the plant to absorb more of the minerals they need at each stage of its life.

An acidity balance in irrigation water compensates for a pH that is too low or too high that can be caused by various minerals.

Balancing acidity in irrigation water will help prevent deficiencies in the plant.

When growing in a soil substrate, the optimal pH range is 6.0 – 7.0

When growing in a hydroponic substrate, the optimal pH range is 5.5 – 6.5

For checking the PH of the soil.

Good for small gardens or growing in pots.

How is PH measured in irrigation water?

There are several ways to measure acidity, which are common and effective either by a digital PH meter, by a drop kit or a stick kit.

Drop kit
Stick kit

How to lower or raise PH?

Usually, heavy rain soils will tend to be more acidic (less than 7), while dry soils will be less acidic (more than 7).

Adding nitrogen-rich fertilizers tends to lower the pH level in the growing medium.

Sulfur or aluminum sulfate can lower ph.

The most common way to lower the PH in drip irrigation or hydroponics is to add Phosphoric acid to every irrigation (called PH down).

This can be found at a garden supply center.

Raising the PH is done by adding compost to the soil.

Adding limestone (calcium carbonate) to the soil will raise the PH also.

Dolomitic limestone contains magnesium, as well as calcium.

The best way to apply sulfur and limestone to your soil is to use a drop spreader (the same machine you may use to apply lawn fertilizer).

This simple machine doesn’t cost very much, and it helps you spread the material more evenly.

It takes around 100 pounds of limestone per 1000 square feet, depending on the initial soil PH, and if it’s sandier or clay.

A common way to raise the PH in drip irrigation or hydroponics is to add Potassium Hydroxide to every irrigation (called PH up).

High Calcium liquid fertilizer, for rapid soil pH change 

In general, soils in climates with high rainfall — such as east of the Mississippi River (particularly east of the Appalachian Mountains) or in the Pacific Northwest — tend to be acidic.

West of the Mississippi, where less rainfall occurs, soil is more alkaline.

But regardless of where you live in the United States, you should easily be able to find the lime or sulfur that you need at your local garden center.

The solution that we use to measure the PH is extracted from the environment near the plant’s roots in the soil, using the soil water sampler, or in hydroponics from the runoff water that is coming out of the pot.

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