Influence of phosphorus and temperature on shrubs

Especially in spring, it is therefore important to consider temperatures when choosing the right fertilizer.

The 10-degree rule

The 10-degree rule (also RGT rule or van’t Hoff rule) states that the reaction rate doubles with a 10°C increase in temperature. This rule applies to all biochemical processes, including all plants.

The growth of shrubs and the associated uptake of nutrients are also temperature-dependent and can only be influenced to a limited extent. An exception is high phosphorus supply in the root area at low substrate temperatures.

Phosphorus availability and soil temperature

There is considerable disagreement about the soil temperature at which plant metabolic activity increases. However, the German agrochemist Horst Marschner has found slowly increasing root respiration and metabolic activity from about 5 °C onward. Further studies with potassium and phosphorus show the strong influence of soil temperature on nutrient uptake. Unlike phosphorus, the uptake capacity of potassium increases significantly faster and more strongly with increasing temperature (see graph).

Influence of temperature on potassium and phosphorus uptake by roots. Source: Mineral Nutrition of Higher Plants, 1997

Compensating the cold effect with phosphorus fertilization

High phosphorus concentrations in the soil solution can significantly reduce this temperature effect and stimulate rooting. Therefore, it is worthwhile to ensure good phosphorus availability early in spring by targeted phosphorus fertilization. One to two applications of 1 g/l Peters Professional Plant Starter 10-52-10 or Universol Yellow 10-30-10 will have the desired effect.