Ugrow Organic: pH & EC

Ugrow are UK distributors for Metrop products. Information on this page is copyright Metrop 2004.

pH Factor

The availability of food elements depends on the PH.
The width of the band shows the intake.

The pH factor of the growing medium is very important, but also the most misunderstood factor.

A plant transports the elements in water, it is therefore important that the elements can be fully incorporated with the water for maximum intake by the plant.

This depends on the PH value of the element.

The best pH value for each medium is between 5.4 and 5.7.

For example: If the PH level is too high, then the Phosphorus, Manganese and Boron intake is significantly reduced, with deficiencies of these elements showing in the plant by 'leaf burn' (each time water is given, it piles up and creates a lens effect) as a result. If the PH is too low, there would not be an optimal intake of all elements, which results in deficiencies again resulting in similar symptoms; 'leaf burn' effect. The get correct PH measurements, readings should be taken from the medium and not in the storage tank or drainage water.

Measuring pH:

The best way to measure this in a hydro or NFT system is to withdraw some water with a syringe from the medium and then to measure it.

With soil or coco you can measure it with a special soil meter however, if you do not own one then follow this simple procedure:

Sample Method: 30 minutes after watering take a wet sample, from the pot.
Place the sample in your hand and push in the pH measurer.
By depressing the medium, fluid is released where the measurer can take a sample.

Following this procedure will ensure you will have the exact pH value of the soil or coco.

The pH depends on the buffer quality of the medium and of the water (amount of bicarbonate). When the buffer is full or just gone then the pH will change to very low or high values. A lot of problems with a too low pH can easily be solved by for example placing a new buffer. AZ grass calcium is a good solution for this, but be careful, too much will increase your pH again.

EC

EC stands for Electrical Conductivity (ms/litre) and with that we measure the amount of useful and useless salts in water. The EC measurer simply measures the amount of electrical resistance, and that also explains why a medium like soil needs to be "wet" to be measured.

An EC measurer measures a total of all nutrition salts. An EC of 0.1/100 litres from one brand might not have the same nutrition value, as one of an EC of 0.1/100 litres from a different brand.

In most general plant foods, there are a lot of elements like chloride, cadmium and other contaminates. These salts will all be measured by EC and can give a false picture of the nutrients available for the crop.

Growers, who select their plants on the basis of crop yield, want to have a large intake of salts (nutrients) for a heavier end result. These salts have to be available in the nutrient solution for absorption in a balanced way, to ensure maximum absorption.

The best way to measure this in a hydro or NFT system is to withdraw some water with a syringe from the medium and then to measure it.

For soil and coco, mix the mediums lightly with distilled/pure water in a cup, and measure it after a short period. Regular water will also work, but will be less reliable.