**3. Criteria for plant sampling**

were obtained from an extensive literature review and also were inserted professional expe‐

Again, it is emphasized that efficient foliar diagnosis includes all procedures starting from

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

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

Table 1 shows some of the factors directly involved in the appearance of real or apparent

Occurrence of illnesses and/or pests causing damage to the aerial or root systems in the plant and

It is a tightly regulated process involving the coordinated expression of specific genes and hormonal participation, mainly cytokinins and ethylene in sequential events and mechanisms that are not well

Extreme environmental conditions (temperature, drought, floods, strong winds), especially in the 10 to

Inadequate application of products or interaction of products like chemical fertilizers, organic matter, fungicides, insecticides herbicides, antibiotics, growth regulators or foliar fertilizers, which could

Inadequate physical and/or chemical soil conditions like poor manipulation, erosion, sharp slopes,

Culture practices inductive of plant abnormal symptoms, like poor irrigation, addition of organic

symptoms, which are similar and confound typical deficiency and toxic patterns.

riences of the authors.

116 Soil Fertility

Biotic

Abiotic

correct field sampling to adequate laboratory analysis.

**2. Factors that affect nutritional diagnosis**

up to the moment the samples are collected for analysis.

deficiency are only eliminated by removing the stress factors.

**Factors Cause**

known [2].

patterns. (Adapted from [1]).

inducing symptoms similar to mineral deficiencies. Natural leaf senescence produces color changes.

15 days before sampling and recent removal of weeds.

prevent absorption of a nutrient and/or simulate deficiency symptoms.

excess aluminum, iron or manganese, low levels of available nutrients.

matter not completely digested, intense pruning and deep soil harrowing.

**Table 1.** Effects of biotic and abiotic factors, that may directly or indirectly induce typical deficiency or toxicity

In this item, sampling criteria will be discussed, in terms of leaf analysis, although it should be emphasized that these principles are also applied in visual diagnosis and indi‐ rect methods.

Sampling is a fundamental step in the outcome of foliar analysis. Poor or inadequate sam‐ pling compromises all available recommendations. Results quality and precision are directly dependent on the procedure. This is a critical step since nutrients concentrations are not the same in all plant parts, and may differ according to age and variety. Foliar analysis results will only be useful and representative of the culture if sampling is correctly performed.

Some criteria are similar to the ones employed in soil sampling and follow basic procedures [3].


Additional important details are:


The sampling must follow recommendations, as discussed above, to produce reliable analyt‐ ical results that will be compared to a standard. The analytical results should be produced

Publications by several authors, [4], [5], [6], [7], [8], [9], [10], [11], report previously defined plant organs, sample numbers and the sampling period for diverse cultures. But to utilize such data as a standard it is necessary to be careful about the physiological age of each plant

Table 2 shows that there is not a standard method of sampling for all cultures. Furthermore, adequate levels of nutrients vary according to different authors emphasizing the care that should be taken to always consider the same author when following a method of collection and in comparing the adequate nutrient levels. It should be noted that adequate levels of


N - 16-20 P - 0,8-2,5 K - 7-20 Ca - 10-30 Mg - 2,5-8,0 S - 2,0-6,0

N - 15-17 P - 0,8-1,2 K - 22-30 Ca - 8-12 Mg - 3-4 S - 2-6

N - 20-24 P - 0,8-1,2 K - 15-20 Ca - 15-25 Mg - 1,5-2,5 S - 4-6

N - 27-36 P - 1,6-2,7 K - 32-54

**Adequate dosages**

**(g kg-1)**

**Macronutrients References**

B - 50-100 Cu - 5-15 Fe - 50-200 Mn - 30-100 Mo - 0,05-1,0 Zn - 30-100

B - 20-40 Cu - 5-10 Fe - 100-200 Mn - 50-200 Mo - Zn - 5-15

B - 25-100 Cu - 5-15 Fe - 50-100 Mn - 15-50 Mo - Zn - 30-50

B - 10-25 Cu - 6-30 Fe - 80-360

**Micronutrients (mg kg-1)**

[4]

Plant Analysis

119

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

[6]

[4]

[4, 5]

by a competent laboratory engaged in a constant quality control program.

chlorine were not described and only some gave values for molibdenium.

and leaf as stated by the author.

Avocado

Pineapple

Acerola Barbados Cherry

Banana

**Culture Plant organ; number of samples and**

50 leaves (1/plant) for each homogeneous plot

50 leaves (1/plant) for each homogeneous plot.

to be sent to the laboratory.

50 leaves (1/plant) for each homogeneous plot.

25 leaves (1/plant) for each

Type of leaf: to sample the 4 sides of the plant, for young leaves totally expanded from fructifying branches.

homogeneous plot less than 4ha. Tree it is recommended to sample the third

Type of leaf: recently matured "D" (generally the 4th leaf from the apex), soon before floral induction. Cut leaves in pieces of 1 cm wide, eliminating the basal portion without chlorophyll. Homogenize and separate about 200 g

crowns.

February to March.

**period of sampling**

Type of leaf: leaves 5 to7 months old, recently expanded from medium height

Recent matured leaves are the usual plant organ analyzed but eventually stem pieces or branch‐ es may be used. In leaves, analysis may be performed in the whole structure or only in specific parts like the lamina or the petiole. In some cases, like in sugar cane, the leaf midrib is removed when foliar diagnosis is desired. In perennial cultures, like coffee or citrus, leaf composition may vary by the presence or absence of fruit in branches. In general, recent matured and physiologi‐ cally active leaves are the plant organs, which better reflect the nutritional status. They respond more readily to variations in nutrient supply and are, thus, better qualified as samples.

Concerning the number of samples, it must be enough to reduce variability and be represen‐ tative of the plant population. In rare occasions, dry material in each sample must exceed 10g (100 to 200g fresh green tissue for most species), but this indicates that different number of samples may be necessary for particular needs of cultures and soils. On average, it is con‐ sidered that 20 single units would be sufficient to compose a sample [1].
