Selecting the Right Plant Tissue Test Package

All the routine plant analysis packages at A&L Great Lakes Laboratories include the elements, phosphorus, potassium, magnesium, calcium, sulfur, sodium, iron, aluminum, manganese, boron, copper, and zinc. The only difference between the packages is the type of nitrogen analysis that is included.

The P1 package does not include any nitrogen analysis. All the other nutrients are included because they are all collected with the same laboratory process. This package is generally used for research and field trials where nitrogen is not a variable.

The P2 package is the standard for all row crops and most specialty crops. This package includes total nitrogen. The nitrogen sufficiency status for nearly all crops is based on total nitrogen.

The P5 package includes nitrate analysis. Nitrate is the mobile form of nitrogen in most plants. So, when analyzing entire leaves, the concentration is generally very low. The nitrate analysis is only appropriate for very few crops and plant parts, primarily potato and tomato petioles. The concept is to capture the fraction of nitrogen that is moving between the leaves and stems so that fertilizer inputs can be adjusted in highly managed specialty crops. For most crops there are no sufficiency ratings for nitrate levels. For that reason, when routine row crop samples are submitted to the lab requesting the P5 analysis, the package will usually be changed to P2.

The P6 package includes both the total nitrogen and nitrate. Again, this package is intended to be used for the same crops as the P5 package. However, any plant submitted requesting the P6 package will receive it since it contains the total nitrogen that will provide sufficiency ratings.

For routine plant tissue testing, the nitrate levels really do not provide any useful information and are often below the minimum reporting limit. The P2 package is the appropriate package 99% of the time. If you are working with a new crop or have questions regarding plant tissue sampling, contact your ALGL agronomist.