**5. Preparation of vegetal material for analysis**

In the laboratory the collected plant material is decontaminated (only the fresh non-dried material), dried, ground, the residual humidity is determined followed by weighing, nu‐ trients quantification and results expressed. More details about the stages in plant analysis, including the determination of macro and micro nutrients is reported in [12] and [8].

### **5.1. Sample decontamination**

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

Type of leaf: 4th from the tip.

Coffee

124 Soil Fertility

Cocoa tree

some cultures.

fections [1].

**period of sampling**

At least 30 days after the 2nd fertilizer portion or after one foliar spraying, in the pinhead phase, that is, before grain filling (December) sample the 3rd or 4th pair of leaves from the apex of productive branches, located in the plant median portion. Collect two pairs of leaves in both sides of the row in a total of 25 plants /homogeneous area sampled (100 leaves/ sample).

18 leaves/ha of a homogeneous plot in

**5. Preparation of vegetal material for analysis**

Type of leaf: 3rd leaf from the tip, mature in plants half-shade.

the Summer.

**Adequate dosages**

**(g kg-1)**

K - 40 Ca - 14-18 Mg - 4 S – 3


N - 29-32 P – 1,2-1,6 K - 18-22 Ca - 10-13 Mg - 3,1-4,5 S - 1,5-2

N - 19-23 P - 1,5-1,8 K - 17-20 Ca - 9-12 Mg - 4-7 S - 1,7-2

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

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‐

In the laboratory the collected plant material is decontaminated (only the fresh non-dried material), dried, ground, the residual humidity is determined followed by weighing, nu‐

**Macronutrients References**

Fe - 500-700 Mn - 250-400 Mo - 0,3-0,5 Zn - 60-70

B - 40-80 Cu - 8-16 Fe - 70-180 Mn - 50-200 Mo - 0,1-0,2 Zn - 10-20

B - 30-40 Cu - 10-15 Fe - 150-200 Mn - 150-200 Mo - 0,5-1,0 Zn - 50-70

[9]

[8]

**Micronutrients (mg kg-1)**

> 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 stages must not take more than 30 seconds.

> 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 cases must be carefully overseen.

#### **5.2. Drying**

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 hours, depending on the vegetal material.

#### **5.3. Grinding**

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‐ tween procedures.

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

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 analysis, limit of detection and cost [13].

In the laboratory the sample will be submitted to the following procedures: weighing, prep‐ aration of the extract and element determination (Figure 1).

The ratio, foliar concentration and production is characterized by different ranges or zones

Plant Analysis

127

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

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

(Figure 3), which should be discussed as detailed by [16].

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

and sufficiency range.

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