plant tissue, tissue analysis, nutrient deficiencies
If you can see something wrong with the crop but can’t figure out the cause, plant tissue analysis may give you the best diagnosis. Tissue analysis is particularly good in determining a nutrient deficiency because these symptoms are hard to tell apart in the field. Nutrient deficiencies are also hard to differentiate from symptoms caused by diseases, herbicide residues, insects, too much to too little moisture, or adverse temperatures. Tissue analysis may be your best bet.
Gerwing, Jim, "Plant Tissue Analysis" (1985). SDSU Extension Extra Archives. 248.