**4. Recommendations about foliar sampling and adequate nutritional levels in some plant species**

To evaluate nutritional status the sample, one plant, a set of plants or a previously deter‐ mined plant part, must be compared to a standard, which consists of a set of nutritionally "healthy" plants. A plant is considered "healthy" when all its tissues show nutrients in ade‐ quate quantities and proportions, it is able to attain high productivity and it looks like the specimens found in very productive cultures. However, the reference culture must be as close as possible of the culture to be sampled and analyzed, and it should be a true represen‐ tative of the peculiar soil-climate characteristics as well as of type of handling and ecological zoning. The reference may have the best productivity but the comparison must be with the same genetic material under the same handling regime and the sampling must follow the same procedures for normal and problem plants.

It is important to establish which plant part it is going to be analyzed in the best period since composition of different parts is not the same and nutrient concentrations also vary accord‐ ing to growth stage.

The previously established physiological stage of the comparison standard must be kept if it is available, or else if this is not existent the start of the reproductive stage should be preferred be‐ ing a period of the highest nutrient concentration. Thus, if a deficiency is detected, it can still be corrected and it will not compromise or minimize the productivity of the next crop.

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

**•** sample collector must make sure hands are clean.

118 Soil Fertility

**•** samples packed in open and perforated paper bags sent to the laboratory two days after collection do not need decontamination and previous field drying procedures. If this is not possible, samples could be treated as already described or a) washed successively in clean water, 0.1% detergent solution, clean water followed by drying in a 70ºC oven or in a sunny environment before being sent to the laboratory and b) samples packed in poly‐ ethylene bags may be kept at low temperatures (2 to -4ºC) for a maximum of 72 hours. 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.

**4. Recommendations about foliar sampling and adequate nutritional**

To evaluate nutritional status the sample, one plant, a set of plants or a previously deter‐ mined plant part, must be compared to a standard, which consists of a set of nutritionally "healthy" plants. A plant is considered "healthy" when all its tissues show nutrients in ade‐ quate quantities and proportions, it is able to attain high productivity and it looks like the specimens found in very productive cultures. However, the reference culture must be as close as possible of the culture to be sampled and analyzed, and it should be a true represen‐ tative of the peculiar soil-climate characteristics as well as of type of handling and ecological zoning. The reference may have the best productivity but the comparison must be with the same genetic material under the same handling regime and the sampling must follow the

It is important to establish which plant part it is going to be analyzed in the best period since composition of different parts is not the same and nutrient concentrations also vary accord‐

The previously established physiological stage of the comparison standard must be kept if it is available, or else if this is not existent the start of the reproductive stage should be preferred be‐ ing a period of the highest nutrient concentration. Thus, if a deficiency is detected, it can still be

corrected and it will not compromise or minimize the productivity of the next crop.

sidered that 20 single units would be sufficient to compose a sample [1].

**levels in some plant species**

ing to growth stage.

same procedures for normal and problem plants.

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‐ 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 and leaf as stated by the author.

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



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

full bloom in the culture.

80 leaves (4/tree) for each homogeneous plot.

florescence.

homogeneous plot.

totally expanded.

Guava c.v. Paluma

Mango

Apple

Papaya

Passion fruit

Peach

Grape

plot.

Autumn.

100 leaves (4/tree) for each homogeneous plot.

100 leaves (1/tree) for each homogeneous plot.

totally expanded.

Type of leaf: recently matured and

**period of sampling**

Type of leaf: 3rd pair of leaves, recently matured (with petiole) from branch extremities, collected in the period of

Type of leaf: middle leaves in branches with flowers in the extremities from the last vegetative flux. Thus, during

100 leaves (4 a 8/plant) for each

Type of leaf: recently matured and

15 petioles of young leaves, totally expanded. (1/tree) for each homogeneous plot. When leaves are mature (17th to 20thleaves from the apex), with a visible axially set flower.

20 laves (1/tree) for each homogeneous

Type of leaf: 3rd or 4thleaf, from the apex of non-shaded branches. (As an alternative, collect a leaf with an axially located floral bud soon to be opened).

**Adequate dosages**

**(g kg-1)**

N - 20-23 P - 1,4-1,8 K - 14-17 Ca - 7-11 Mg - 3,4-4 S - 2,5-3,5

N - 12-14 P - 0,8-1,6 K - 5-10 Ca - 20-35 Mg - 2,5-5 S - 0,8-1,8

N - 19-26 P - 1,4-4 K - 15-20 Ca - 12-16 Mg - 2,5-4 S - 2-4

N - 10-25 P - 2,2-4 K - 33-55 Ca - 10-30 Mg - 4-12 S -

N - 43-55(33-43) P - 2,3-2,7(1,2-2,1) K - 20-30(22-27) Ca - 9-25(12-16) Mg - 1,9-2,4(2,5-3,1)

S - 3,2-4

N - 30-35 P - 1,4-2,5 K - 20-30 Ca - 18-27 Mg - 3-8 S - 1,5-3

N - 30-35 P - 2,4-2,9

**Macronutrients References**

B - 20-25 Cu - 20-40 Fe - 60-90 Mn - 40-80 Mo - Zn - 25-35

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

B - 25-50 Cu - 6-50 Fe - 50-300 Mn - 25-200 Mo - 0,1-1,0 Zn - 20-100

B - 20-30 Cu - 4-10 Fe - 25-100 Mn - 20-150 Mo - Zn - 15-40

B - 40-100 Cu - 10-15 Fe - 120-200 Mn - 40-250 Mo - 1,0-1,2 Zn - 25-60

B - 20-60 Cu - 5-16 Fe - 100-250 Mn - 40-160 Mo - Zn - 20-50

B - 45-53 Cu - 18-22

**Micronutrients (mg kg-1)**

[7]

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[6]

[6]

[6]

[4]

[4]

[6]


leaf from the apex when the

eliminate the central rib.

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

25 leaves (1/plant) for each homogeneous plot less than 4ha. For the banana tree it is recommended to sample the third leaf from the apex, when the inflorescence shows all the uncovered female bunches (without bracts) and not more of three male flower bunches. Collect 10 a 25 cm of the internal median part of the limb, and eliminate the central rib. For varieties: Prata, Anã, under

peripheral halves.

irrigation regimens

homogeneous plot.

homogeneous plot.

diameters.

sprouting.

100 leaves (4leaves/tree), for each

100 leaves (4 leaves/tree) for each

Type of leaf: recently matured and totally expanded leaf, in the middle portion of a branch, 3 months after

Type of leaf: 3rd leaf from the fruit. Leaf born in the spring, 6 months old, in branches with fruit 2 to 4cm in

Banana

120 Soil Fertility

Banana

Orange

Fig

**period of sampling**

inflorescence shows all the uncovered female bunches (without bracts) and not more than three male flower bunches. Collect 10 to 25 cm of the internal median part of the limb and

For varieties: Nanica, Nanicão e Grande Naine,under irrigation regimens.

Type of leaf: the 5-10 cm central part of the 3rd leaf from the inflorescence, eliminating the central rib and the

**Adequate dosages**

**(g kg-1)**

Ca - 6,6-12 Mg - 2,7-6 S - 1,6-3

N - 27-36 P - 1,8-2,7 K - 35-54 Ca - 3-12 Mg - 3-6 S – 2,5-8

N - 25-29 P - 1,5-1,9 K - 27-35 Ca - 4,5-7,5 Mg - 2,4-4,0 S - 1,7-2

N - 23-27 P - 1,2-1,6 K - 10-15 Ca - 35-45 Mg - 2,5-4,0 S - 2-3

N - 10-25 P - 1,0-3,0 K - 10-30 Ca - 30-50 Mg - 7,5-10 S - 1,5-3,0

**Macronutrients References**

Mn- 200-1800

Mo - Zn - 20-50

B - 10-25 Cu - 6-30 Fe - 80-360 Mn- 200-2000

[6]

[11]

[6]

[4]

Mo - Zn - 20-50

B - 25-32 Cu - 2,6-8,8 Fe - 72-157 Mn - 173-630 Mo - Zn - 14-25

B - 36-100 Cu - 4-10 Fe - 50-120 Mn - 35-300 Mo - 0,1-1,0 Zn - 25 - 100

B - 30-75 Cu - 2-10 Fe - 100-300 Mn - 100-350 Mo - Zn - 50-90

**Micronutrients (mg kg-1)**


the end of flowering.

General lythea 3rdleaf

main rib

main rib.

emergence.

the tip.

Soybean

Sugarcane (Plant)

Sugarcane (Ratoon)

Potato

Onion

**period of sampling**

Type of leaf: leaves of the upper third.

30 leaves/ha of a homogeneous plot at

Type of leaf: first matured leaf from the branch end, excluding the petiole.

20-30 leaves/ha of a homogeneous plot Type of leaf: leaf +3; leaf +1 = with the first ligula (=membranous outgrowth at the junction between the leaf blade and the sheath). Median third excluded the

20-30leaves/ha of a homogeneous plot,

Type of leaf: leaf +3; leaf +1 = with first ligula (=membranous out growth at the junction between the leaf blade and the sheath). Median third excluded the

30 leaves/ha of a homogeneous plot, in the middle of the cycle, 30-45 days after

Type of leaf: Petiole of the 4ty leaf from

40 tip leaves/ha of a homogeneous plot

at the middle of the cycle. Type of leaf: the highest one.

Tomato 40 leaves/ha of a homogeneous plot in full flowering, or first ripe fruit;

4 month after sprouting.

**Adequate dosages**

**(g kg-1)**

K - 20-24 Ca -17-22 Mg - 9-11 S - 5-7

N - 45-55 P - 2,6-5,0 K - 17-25 Ca - 4-2 Mg - 3-10 S - 2,5


N - 19-21 P - 2-2,4 K - 11-13 Ca - 8-10 Mg - 2-3 S - 2,5-3

N - 20-22 P - 1,8-2 K - 13-15 Ca - 5-7 Mg - 2-2,5 S - 2,5-3


N – 30 P - 3,5 K - 50 Ca - 20 Mg - 7,5 S - 3,5

N – 40 P - 3 K - 40 Ca - 4 Mg - 4 S – 7

N – 30 P - 3,5

**Macronutrients References**

Fe - 150-300 Mn - 300-600 Mo - Zn - 70-140

B - 21-55 Cu - 10-30 Fe - 51-350 Mn - 21-100 Mo - Zn - 21-50

B - 15-50 Cu - 8-10 Fe - 200-500 Mn -100-250 Mo - 0,15-0,3 Zn - 25-30

B - Cu - 8-10 Fe - 80-150 Mn - 50-125 Mo - Zn - 25-30

B - 40-50 Cu - 5-8 Fe- 800-1000 Mn - Mo - Zn -

B - Cu - Fe - Mn - Mo - Zn -

B - 50-70 Cu - 10-15

**Micronutrients (mg kg-1)**

[8]

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[8]

[8]

[8]

[8]

[8]


Corn

122 Soil Fertility

Sorghum

Eucalyptus

Pinus

Peanut

**period of sampling**

Type of leaf: the youngest, recently matured, from branch apices.

30 leaves/ha, of a homogenous plot showing female inflorescence (hair). Type of leaf: leaf obsta and below the

30 leaves/ha of a homogeneous plot at

18 leaves/ha of a homogeneous plot, in

Type of leaf: recently matured primary branches in the superior third of the

18 leaves/ha of a homogeneous plot in

Type of leaf: Recently matured , primary

30 leaves/haof a homogeneous plot at

Type of leaf: 4th leaf of the main stalk from the basis (1ª = above the cotyledon air ebrabches).

corn ear

the start of tillering. Type of leaf: median

Summer- Autumn.

Summer-Autumn.

the start of flowering.

Sunflower 30 leaves/ha of a homogeneous plot at the start of flowering.

plant.

**Adequate dosages**

**(g kg-1)**

K - 15-20 Ca - 13-18 Mg - 4,8-5,3 S - 3,3-3,8


N - 27,5-32,5 P - 2,5-3,5 K - 17,5-22,5 Ca - 2,5-4 Mg - 2,5-4 S - 1,5-2

N - 13-15 P - 4,0-8,0 K - 25-30 Ca - 4-6 Mg - 4-6 S - 0,8-1


N - 14-16 P - 1-1,2 K - 10-12 Ca - 8-12 Mg - 4-5 S - 1,5-2

N - 12-13 P- 1,4-1,6 K - 10-11 Ca - 3-5 Mg - 1,5-2 S - 1,4-1,6


N – 40 P - 2 K - 15 Ca - 20 Mg - 3 S - 2,5

N - 33-35 P - 4-7

**Macronutrients References**

Fe - 97-105 Mn - 67-73 Mo - Zn - 30-35

B - 15-20 Cu - 6-20 Fe - 50-250 Mn - 50-150 Mo - 0,15-0,2 Zn - 15-50

B – 20 Cu - 10 Fe - 200 Mn - 100 Mo - Zn – 20

B- 40-50 Cu - 8-10 Fe - 150-200 Mn - 100-600 Mo - 0,5-1 Zn - 40-60

B - 20-30 Cu - 5-8 Fe - 50-100 Mn - 200-300 Mo - 0,1-0,3 Zn- 34-40

B - 140-180 Cu - Fe -

Mn - 110-440 Mo - 0,13-1,39

Zn -

B - 50-70 Cu - 30-50

**Micronutrients (mg kg-1)**

[8]

[8]

[8]

[8]

[8]

[8]


trients quantification and results expressed. More details about the stages in plant analysis,

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According to [12], when only macro nutrients are to be determined in samples washing may be plain, to eliminate gross contaminations like dust. Just shaking the sample under tap wa‐ ter and rinsing with distilled water will be enough but the procedure must be fast to avoid the loss of soluble elements. Procedures are more elaborate when determination of microele‐ ments is contemplated. In this case the samples must be successively washed in tap water, dilute non -ionic detergent (0.1%, v/v), distilled water to remove detergent, 0.1M HCl, distil‐ led water and finally deionized water. With samples highly soiled the battery of solvents must be changed as necessary. To avoid loss of soluble inorganic constituents the washing

Contaminations by pesticides and foliar fertilizers (especially when applied with surfactants in the spraying mixture) are difficult to remove by washing. Collection of samples in these

Drying of samples must be as fast as possible to minimize biological and chemical altera‐ tions. After eliminating excess water, samples packed in paper bags are dried in 65 to 70ºC ovens fitted with devices for forced air circulation [12]. According to [1] temperatures must be higher, 70 to 80ºC to avoid putrefaction especially if samples are too close together. Sam‐ ples should be kept in the oven till constant weight, which will be attained after 48 to 72

Mills provided with stainless steel or plastic chambers are recommended to grind the vege‐ tal material to reduce to a minimum contamination by micronutrients like Fe and Cu. Grind‐ ing is necessary to homogenize samples for analytical determinations and it must produce material that can be sieved through 1 to 20 mesh when using Wiley type mills. When alter‐ nating grinding of different samples mills are cleaned by brushing with 70% alcohol be‐

Chemical quantification of nutrients is the next step in the diagnosis of the nutritional status of a foliar sample. Several factors are involved in the choice among the different analytical methods available for this purpose. Some of them are: safety (hazard or toxicity), equipment available, type of element to be determined, precision and accuracy, period of time taken by

**5.4. Chemical analysis: extraction and determination of nutrients**

including the determination of macro and micro nutrients is reported in [12] and [8].

**5.1. Sample decontamination**

stages must not take more than 30 seconds.

hours, depending on the vegetal material.

analysis, limit of detection and cost [13].

cases must be carefully overseen.

**5.2. Drying**

**5.3. Grinding**

tween procedures.

**Table 2.** Procedures for leaf collection and ranges considered adequate of macro and micro nutrients contents in some cultures.

The table shows how important it is to follow the same recommendation (standard) for sam‐ pling and after the comparison of results. Collection mistakes that lead to wrong diagnostics and recommendations are common. It is emphasized that the main factors responsible for different nutritional levels in plants are:1- plant age; 2- organ analyzed; 3-type of plant (spe‐ cies, variety, graft/stock, crown);4- period of the year; 5- method of sample cleaning, extrac‐ tion and quantification of nutrients; 6- water percentage in soil (for nutrients determined in the sap); 7- time of day (for nutrients determined in the sap);8- inadequate production of dry matter from the plant due to isolated or interative soil, climate, genotypic or human imper‐ fections [1].
