Laboratory Analysis of Plant Samples Techniques
Numerous methods have been developed for the analysis of plant tissue. Most procedure require that the organic matter be burned away first, leaving the various elements to be analyzed. Some scientists have proposed the use of extraction procedures which utilize dried, green tissue.
These techniques, however, have been developed only for a few crops and elements.
Method of Ashing
The ignition of a plant sample should be carried out at a low temperature, in order to avoid any loss of volatile, mineral constituents. This is especially important if the individual minerals left in the ash are to be subsequently determined.
A dry ashing method is normally carried out in a muffle furnace at temperatures not exceeding 5000C. Ashing may require two hours or more depending on the type of tissue.
Tissue which is highly carbonaceous may need a longer ashing period. The use of high-wall crucibles is preferred over flat vessels for holding the materials.
Wet ashing can be done using various combinations of HNO3-H2SO4– HC104. Aluminum block digestors are also recommended for this ashing process.
Read Also: Principles of Plant Analysis Data Interpretation
Method of Analysis
Various analytical methods are available for the analysis of plant – tissue ash. It is difficult to select any one method or techniques as superior over another. Those listed below are the most commonly used.
- Colorimetric
- Flame emission
- Atomic absorption
- Mass spectrometry
- X-ray fluorescence
- Neutron activation analysis
- Folarography
Small changes in the concentration of elements found in a plant may result in substantial changes in its growth. For this reason, precision is important in any analysis, regardless of the method chosen.
Techniques used in sample preparation, ashing and analysis need to be standardized in order to obtain results which are both accurate and reproducible. This is essential, along with good standard reference samples.
Interpreting Analysis Data
Data which are both reliable and interpretative are lacking for a number of plant crops. This is particularly true for those crops in their initial stages of growth, with concentration values were sought; but it became evident, after continued study, that a plant’s nutrient status could be more accurately described using concentration ranges.
Comparing a plant’s concentration of elements with its sufficiency range, is a procedure which is commonly used. The concentration of each element found during analysis is reported as “less than” “greater than” or “within the range”. For successful, corrective treatments, data on soil analysis and cultural practices are necessary.
In conclusion, plant tissue tests are used in conjunction with soil tests to obtain a complete picture of plant nutrient requirements.
Fertilizer recommendations must be based on both soil analytical data, crop response to fertilizer added in the field and plant analysis.
The data therefore must be correctly interpreted by knowledgeable soil scientists to facilitate high crop yield and quality, economic returns and environmental protection.
Read Also: Methods of Sampling Plant Tissue
