**2. Factors that affect nutritional diagnosis**

It is important to know the main factors that interfere in the diagnosis of plant nutritional status, so that confident analytic results are obtained and compared to pre-established litera‐ ture standards. The composition of the vegetal tissue reflects the interaction of factors acting up to the moment the samples are collected for analysis.

Initially, it is necessary to exclude biotic and abiotic factors that affect nutrient concentra‐ tions in plants. Among these should be considered, lack or excess of water, high or low tem‐ peratures winds, pests and illnesses, compacted or poorly plowed soils, mechanical damage and herbicide toxicity [1]. These and other factors may produce deficiency symptoms in the plant by preventing absorption and/or translocation of nutrients. In such cases symptoms of deficiency are only eliminated by removing the stress factors.

Table 1 shows some of the factors directly involved in the appearance of real or apparent symptoms, which are similar and confound typical deficiency and toxic patterns.


**Table 1.** Effects of biotic and abiotic factors, that may directly or indirectly induce typical deficiency or toxicity patterns. (Adapted from [1]).

To exclude the factors in Table 1, the professional must know the interactions "plant-envi‐ ronment-soil – farming activity" before proceeding to sampling.
