Plant tissue testing (Part 2): Making sense of results

By Greg LaBarge

Last month, I discussed best sampling practices for collecting leaf tissue for nutrient analysis: This month, we will cover using the results to make nutrient decisions.

The lab results you receive typically report nutrients in two different ways. The macronutrients of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) are found in higher quantities in the plant and reported as a percentage of the total biomass. Micronutrients of Manganese (Mn), iron (Fe), boron (B), copper (Cu), zinc (Zn), and molybdenum (Mo) are reported as the plant concentration using the units parts per million (ppm). As we have preached in the interpretation of soil test results, it is important to note these units and see that they match the sufficiency tables you use for comparison.

One common soil-plant growth interaction seen in tissue testing occurs with P and K. There is a significant and positively correlated linkage between soil tests P and plant P, and soil tests K and plant K, irrespective of other soil factors.… Continue reading