When and How to Sample Plants
Table 1 and Figure 1 outline the proper stage of growth, plant part, and number of plants to
sample for major agronomic and horticultural crops. Similar information is depicted in figures
on the last page of this publication. If a crop is sampled at other times in the growing season, the
analysis will be provided but may not be interpreted on the University of Wisconsin plant
analysis report. However, when plant analysis is being used to confirm a suspected nutrient
deficiency, the samples should be taken as early int he season as possible so that the deficiency
can be corrected and minimize the potential yield loss. Plants showing abnormalities usually
continue to accumulate nutrients even if growth is impaired by some limiting factor.
Samples should not be taken from plants that obviously have been stressed from causes
other than nutrients. Do not take samples from plants that —
· Are dead or insect damaged;
· Are mechanically or chemically injured;
· Have been stressed by too much or too little moisture (i.e., flooding or drought);
· Have been stressed by abnormally high or abnormally low temperature.
Sample Normal and Abnormal Areas
When a nutrient deficiency is suspected (even without visual symptoms), or there is a need
to compare different areas in a field, it is recommended that similar plant parts be collected
separately from both the affected plants and adjacent normal plants that are at the same stage of
growth. In this way, a better evaluation can be made between the nutritional status of healthy
and abnormal plants of the same variety grown under the same conditions.