While plant activity accounts for most of the pH fluctuations, there are also other causes which might either mask what the plant is doing or add to it.

Microbes

Microbial activity is similar to that of plants and contributes carbon dioxide to the medium or nutrient solution. This microbial activity can be quite marked and will contribute to the acidity.

Among commercial growers there is a strong trend towards adding beneficial microbes and/or a supporting substrate to growing systems to improve the root environment. This trend has gathered pace over the last four or five years. At the moment, the only place you will find this hybrid organic/conventional technology is in Canadian Xpress nutrients. This fusion nutrition was introduced in 2004 as a world first and we expect to see most manufacturers following this lead as its benefits are realized.

If you are using this nutrient, you can therefore expect different pH fluctuations from what you are used to.

Water

The water that you are using will have its own influence on pH. Hard water raises it and rain or acidic water will lower it. The pH value of water can be sometimes quite variable which is why it pays to measure it frequently. Not because it will vary so much that it will cause major problems but mainly so a grower won’t get any nasty surprises and is ready for the changes.

Management of pH

Generally, the pH can be managed by using a nutrient suited to the water, a pH meter or indicator solution, and the appropriate “pH Up” or “pH Down” additive.

We do need to mention growers in hard water areas. Your problem is that the buffering capacity of the water is so high that you need to use huge amounts of pH Down to control the pH. In this situation, even though the pH may not be over 8, the chemical composition of the water is such that it takes a lot of acid to get it down. In this case, you would be better off putting the water through a reverse osmosis machine first. Your crop will be substantially better off using r