Use of petiole samples
- Use petiole samples for analysis of nitrogen (as nitrate-N), phosphorus and potassium.
- Use whole leaf samples for other nutrients.
- Samples should be taken from the youngest fully expanded leaf.
- The earliest time a sample can be taken is when a plant has 6 – 8 leaves.
- Early sampling may enable remedial action to be taken if a nutrient is deficient.
- Use the data below to check nutrient levels.
- Do not use threshold levels from the laboratory, as these do not account for the stage of development of your crop.
- If a nutrient is deficient, check the appropriate page for further information.
Taking petiole samples
- Walk across a field in a “W” pattern, taking samples of the youngest fully expanded leaf.
- The youngest fully expanded leaf is generally the fourth leaf below the growing tip.
- A potato leaf is a compound leaf comprising a central petiole / midrib and leaflet blades.
- Remove the whole leaf from the stem.
- Strip off and discard the leaflet blades.
- A sample should comprise sufficient petioles to fill a standard 1/2 pint mug.
- More leaves will have to be picked to make up a petiole sample than a whole leaf sample, particularly early in development when leaves are small.
Target concentrations of nutrients in petiole samples