Pistachio Zinc deficiency
Estimating soil nutrient content
Soil micro-nutrients can be quite difficult to measure - due to issues of sample contamination.
Laboratory methods. : The American Society of Agronomy have a series of excellent publications outlining laboratory methods for soil analysis Link
Micro-nutrient deficiencies are increasingly observed - especially in heavily cropped areas. There are 7 micro-nutrients essential for plant growth:
Soil nutrient deficiencies
Plant deficiency symptoms: Plant deficiency symptoms often are one of the best indicators of possible deficiency or excess (Link).
Soil pH: Soil pH can be a good indicator of the probability of a nutrient deficiency Link (requires flash)
Simple tests for identifying deficiencies: There are a number of simple tests for identifying possible plant nutrient deficiencies (Link)