Liebig's Law

(or the Law of the Minimum)

An important concept to understand when dealing with plants (like algae) is Liebig’s Law or the Law of the Minimum. This concept was formulated by German chemist Justus von Liebig, often called the “father of the fertilizer industry”.

Imagine you are building a dog house using nails and boards. As long as you have both, you can continue building. When you run out of nails, you have to stop building. Nails (or rather lack of nails) are “limiting” your building process. So you buy a 5 pound box of nails and return to work. Inevitably, you will run out of boards next. Even though you still have plenty of nails, you need more boards to continue building. Now boards are “limiting”. You could call the home store and have an entire semi truckload of nails brought to your house, but it won’t help the doghouse get built, because you need boards.

This is an example of Liebig’s Law of the Minimum, which states that plant growth will continue as long as all required factors are present (e.g. light, water, nitrogen, phosphorus, potassium etc.). When one of those factors is depleted, growth stops. Increasing the amount of the “limiting” component will allow growth to continue until that component (or another) is depleted.

The nutrient most typically “limiting” algae growth in lakes is phosphorus. If phosphorus concentrations can be controlled, then algae can be controlled…usually. Sometimes, other nutrients or conditions can limit algae. In Mark Twain Lake, for example, light is the factor that most often limits algae.

Tony Thorpe

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