Plant analysis provides two approaches to enhancing fertilizer effectiveness. One is the diagnostic approach where plant analysis is made when there is an obvious growth problem in the field. A sample is taken from the poor growing area and compared to a sample from an adjacent normal growing area.

Ward Laboratories, Inc. suggests using this diagnostic approach to researching production problems. The comparative samples are very important for proper interpretation of the analysis. The cost for comparative testing is first sample at regular fee, second sample at one-half the regular fee.

The monitoring approach is used to confirm that the plant had proper nutrition. Plant samples should be taken when the crops are in the bloom (reproductive) stage of growth. Samples taken earlier than bloom stage contain higher levels of nutrients while samples taken during grain fill will be lower. For this reason it is very important to identify the growth stage for proper interpretation.