What is the three digit N-Tester value and how to interpret it?

The N-Tester determines the relative amount of chlorophyll present by measuring the light absorbance of the leaf at two wavelengths. The measurement result is expressed as the three digit N-Tester value.

What is the N-Tester value?

The N-Tester value is a relative measure of the chlorophyll concentration in the leaf. It has no unit and the range of values has been chosen to be easy to use for monitoring nitrogen levels.

Due to the almost linear relationship between chlorophyll and nitrogen content, the N-Tester value, together with crop and region specific data in YaraPlus Atfarm, can be used to determine whether the plant is under or over supplied with nitrogen. A nitrogen recommendation in kg/ha can be derived from this.

How to interpret the N-Tester value?

Each N-Tester reading has an associated N-Tester value. On the measurement results screen in the YaraPlus mobile app, you can view the N-Tester value of each measurement by clicking Single measurements (N-Tester BT only). Click on a value to highlight its location on the map (N-Tester BT only).

The more nitrogen absorbed by the plant, the higher the chlorophyll concentration and therefore the higher the photosynthetic output – which has a particular effect on grain yield, grain quality and protein content. If you're fertilising from a deficient supply, the N-Tester value will increase as nitrogen levels improve over the weeks.