What factors can affect the N-Tester reading and which do not?

These factors can affect the N-Tester reading:

• Growth stage: Measure plants at the correct growth stage (BBCH 30-51). Measurements on less developed leaves may lead to higher recommendations.
• Atypical leaves: Avoid measuring grained or thick leaf tips, and plants with visible drought stress, such as rolled leaves. Intense drought can lead to increased chlorophyll concentration in leaves and false N-Tester readings.
• Atypical field areas: Avoid measuring areas with distinctly different soil properties, such as sand banks or similar.
• Sulfur deficiency: A sulfur deficiency, like a nitrogen deficiency, will make the leaves lighter and the nitrogen recommendation may not be correct. Other nutrients have no significant effect.

These factors won't affect the N-Tester reading:

• Time of day
• Pesticides
• Moisture on the leaf
• Strobilurin use
• Yield level