(Quantitative or semi-quantitative) chemical analysis of plants (or plant parts) aims to determine whether nutrients in the plant tissue (dry or fresh) are present in a concentration range that allows for normal growth and development.

In Germany, the relationship between nutrient concentration and yield is divided into 5 zones (see also the section "Symptoms"):

a) Zone where yield increases while concentration decreases. This is known as the Steenberg effect, occurs only under severe deficiency, and is thus a rare special case without practical significance.

b) Zone where yield increases at an almost constant concentration. Here, the growth rate is controlled (limited) by nutrient supply, and deficiency symptoms may appear.

c) Zone of latent deficiency. Yield increases with rising plant concentration and reaches a critical concentration at the border of maximum yield. This concentration value is called the yield threshold value. Concentrations above this threshold are either:

d) Sufficient or optimal and do not influence yield, or

e) Too high, leading to toxicity and yield reduction.Bei der Interpretation von Analysenergebnissen geht es also darum herauszufinden, in welchem Bereich der Kurve sich eine Pflanze befindet.

Analogous to soil analysis, the procedure for plant analysis consists of a series of sequential steps, starting with sampling and ending with the interpretation of the analysis result. These steps are summarized in the diagram below.

During growth, the critical concentrations in plant tissue change (see below). Furthermore, they differ among various plant organs. This has led to the development of very detailed descriptions and instructions for selecting plants/plant parts for plant analysis, which must be followed to obtain interpretable results.

In dry and wet years, the nutrient contents [in plants] can differ even on the same soil. This can be attributed to the varying conditions for nutrient transport through the soil to the plant root (see Mass Flow and Diffusion).

There are extensive tabulated references for the nutrient sufficiency ranges of all major crops. These are often specific to certain plant parts. Caution is therefore required when applying these tables if all necessary information is not available (e.g., tables from other countries, etc.).