Plant Nutrition: Part 1

Managing plant nutrition is crucial to successful hydroponic production. In this issue, we discuss the macro-elements nitrogen, potassium and phosphorus, and their interaction with one another.

Many hydroponic nutrient formulations are available today, but all are fairly similar. Most differ merely in the ratio of nitrogen to potassium; there is no ‘secret ingredient’ that makes one formulation better than the other.

The rationale behind the different nitrogen-to-potassium ratios is the fact that plants require less nitrogen during short or dark days (as found in Europe, for example) and more nitrogen during long, sunny, hot days (as found in Africa).

Sixteen mineral elements are considered essential for the growth of plants. These are divided into macronutrients (macro-elements), which are required in relatively large quantities, and micronutrients (trace elements), which are needed in considerably smaller amounts.

Macro-elements include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), potassium (K), phosphorus (P), calcium (Ca), magnesium (Mg) and sulphur (S).

Trace elements include iron (Fe), chlorine (Cl), manganese (Mn), boron (B), copper (Cu), molybdenum (Mo) and zinc (Zn).

NITROGEN

Nitrogen is a critical component of proteins required for plant growth, and is even found in chlorophyll, which gives plants their green colour.

Plants utilise nitrogen in two forms: ammonium and nitrate. The latter is the most available inorganic form for the plant; the ammonium form of nitrogen encourages vegetative growth.