**6. Interpretation of analytical results**

Results are interpreted by comparing the concentration values of each element in the sample with the respective standard or a value considered optimal.

The foliar chemical analysis may be expressed in different methods, the most used are: 1- in the single variable methods only one of the elements is selected and the results are ex‐ pressed by the deviation of the optimum percentage, the critical level and the sufficiency range; 2- the relation between the concentration values of nutrients is the basis for the dou‐ ble variable method named DRIS (Diagnosis and Recommendation Integrated System), or 3 the multivariable method named NCD (Nutritional Composition Diagnosis).

The flow chart in Figure 2 shows all the steps involved in foliar diagnosis starting with sam‐ pling up to the results obtained.

#### **6.1. Sufficiency range**

Most cultures do not have a single definite point for optimal production but a range of nu‐ trient concentrations. Thus, it is adequate to recommend degrees of fertilization to keep nu‐ trients slightly above the critical level, but included in the sufficiency range [14]. However, both have limitations the critical level by its precise character and the sufficiency range for lack of precision due to very wide limits.

The use of the sufficiency range is an attempt to extend a single optimal point into an opti‐ mal range and to make sure that at its highest level the culture is adequately supplied and at the lowest level it is so deficient that production will be negatively affected [1]. Generally, the sufficiency range corresponds to 90-100% of maximal production [15]. Also, the lowest limit of the sufficiency range will be the minimal critical point and superior limit the toxic critical point [1].

The ratio, foliar concentration and production is characterized by different ranges or zones (Figure 3), which should be discussed as detailed by [16].

In the laboratory the sample will be submitted to the following procedures: weighing, prep‐

**Figure 1.** Simplified schematic procedure of foliar analysis to be conducted in a plant nutrition laboratory.

Results are interpreted by comparing the concentration values of each element in the sample

The foliar chemical analysis may be expressed in different methods, the most used are: 1- in the single variable methods only one of the elements is selected and the results are ex‐ pressed by the deviation of the optimum percentage, the critical level and the sufficiency range; 2- the relation between the concentration values of nutrients is the basis for the dou‐ ble variable method named DRIS (Diagnosis and Recommendation Integrated System), or 3-

The flow chart in Figure 2 shows all the steps involved in foliar diagnosis starting with sam‐

Most cultures do not have a single definite point for optimal production but a range of nu‐ trient concentrations. Thus, it is adequate to recommend degrees of fertilization to keep nu‐ trients slightly above the critical level, but included in the sufficiency range [14]. However, both have limitations the critical level by its precise character and the sufficiency range for

The use of the sufficiency range is an attempt to extend a single optimal point into an opti‐ mal range and to make sure that at its highest level the culture is adequately supplied and at the lowest level it is so deficient that production will be negatively affected [1]. Generally, the sufficiency range corresponds to 90-100% of maximal production [15]. Also, the lowest limit of the sufficiency range will be the minimal critical point and superior limit the toxic

the multivariable method named NCD (Nutritional Composition Diagnosis).

aration of the extract and element determination (Figure 1).

**6. Interpretation of analytical results**

pling up to the results obtained.

lack of precision due to very wide limits.

**6.1. Sufficiency range**

126 Soil Fertility

critical point [1].

with the respective standard or a value considered optimal.

**Figure 2.** Flow chart for evaluation of the nutritional status of plants and its expansions according to the critical level and sufficiency range.

**Figure 3.** Relation of nutrient concentration and relative production.

**1.** In the deficient range or zone the symptoms are visible and occur in soils (or substrates) very deficient in an element due to insufficient dosages. In these conditions the re‐ sponse in production of dry matter is high, the element concentration is not increased and it may even be diluted. The nutrient dilution effect caused by organic matter forma‐ tion is known as the Steembjerg effect. When the concentration of a plant nutrient is set in this range it is considered deficient.

sideration of well-known and documented interactions between elements is severely criti‐

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http://dx.doi.org/10.5772/53388

The deviation from the percentage optimum (DPO) is an improvement of the critical level method [19]. It evaluates each nutrient concentration in relation to the optimum value (me‐ dian of the sufficiency range) by the expression: DPO= [(Cx100/CR)-100] where C is an ele‐ ment concentration in the sample dry matter and CR it is the optimal concentration for the same conditions (culture, tissue analyzed, manipulation, plant development stage etc.). In

This is a procedure not common in the literature but it permits the evaluation of the nutri‐ tional status of the plant and the arrangement of the elements as a function of the degree of deficiency. However, the limitation order is not representative because element interactions

DRIS is an alternative to the conventional method for the determination of the nutritional status of a plant [20]. It considers nutrient interactions in the diagnostic process, which is conducted by the combination of all the relations in the form of ratios [20] or products [21]. In this technique indexes, which express nutrient equilibrium in a plant or culture are calcu‐ lated for each one, as a function of concentration ratios of each element and the total and compared in groups of two to other ratios considered standard or norms obtained in a pop‐

Foliar diagnosis, in this method, aims to adjust fertilization, so far only recommended by soil fertility and culture productivity, by additional production gains and correction of defi‐ ciencies. It also makes possible the management other nutrient availabilities, possibly reduc‐ ing them and permitting an equilibrated fertilization, in view of the culture nutritional

The method relates nutrient concentrations in a multivariable form, as a function of ratios of each nutrient concentration and the geometrical mean of the nutritional composition of the sampled tissue [23]. The method is not widely used although it deals with relations between

DNC and DRIS are independent calibration methods, since use of double or multi variable methods minimizes non controlled effects of accumulated biomass, in contrast to the critical level, which needs calibration assays conducted in places and different years, and maintain control on other production factors (including other nutrients) and on a supply adequate to

the absence of the sufficiency range the critical level is taken as the optimum value.

cized in these methods [17, 18].

ulation of highly productive plants.

**6.4. Diagnosis of nutritional composition (DNC)**

necessities.

all elements analyzed.

full plant development [24].

**6.2. Deviation from the percentage optimum**

are not considered and the conventional table is still used.

**6.3. Diagnosis and Recommendation Integrated System (DRIS)**


Although plant tissues show absorption of the increased nutrient concentrations this is not expressed in increased growth. Thus, the element concentration in this range, which corre‐ sponds to maximal or optimal production and it is below the toxicity critical point, is consid‐ ered to be high.

**4.** The toxicity range or zone starts when increased nutrient concentrations significantly reduce production. Reductions of 5% up to 20% indicate toxic levels. The condition is observed in soils (or substrates) with excess nutrients receiving additional dosages that are absorbed as shown by increased tissue concentrations but expressed in decreased growth and/or imbalance in relation to other nutrients.

The critical level of deficiency is a factor largely employed in research and it corresponds to an optimal nutrient concentration. Below it the growth index (production or quality) is sig‐ nificantly decreased and above it, production represents poor economics.

After attaining maximal production, increased nutrient concentrations will not result in growth but in plant "luxury consumption". During this period nutrients accumulate in cell vacuoles and may be gradually liberated to supply eventual plant nutritional necessities. As already stated nutrient concentrations above the level of luxury consumption can lead to de‐ creased production and characterize the toxicity range.

Interpretation of foliar nutrient concentrations based on the critical level and the sufficiency range is made directly by comparison with standard values. The plant nutritional status (de‐ ficiency, sufficiency, luxury consumption) is defined independently for each element by the range of values found for the sample. However, the plant mineral composition is the result of its adaptation to an environment under the action of several limiting factors. Lack of con‐ sideration of well-known and documented interactions between elements is severely criti‐ cized in these methods [17, 18].
