SOIL FERTILITY EVALUATION Flashcards
TECHNIQUES USED TO ASSESS NUTRIENT STATUS OF A SOIL
- Nutrient Deficiency Symptoms
- Plant Analysis
- Biological Tests (pot test, field experiments, microbiological test)
- Soil Analysis or Soil Testing
Principle: When plant nutrients are not adequately supplied by the soil or are not utilized by the crop, specific biochemical or enzyme activities are adversely affected. These are reflected by physiological processes causing the plant to display an appearance from normal.
Nutrient Deficiency Symptoms
2 Advantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
- Cheap; needs no elaborate equipment but require skill.
- Quick; needs no chemical analysis required to identify the problem.
- Cheap; needs no elaborate equipment but require skill.
- Quick; needs no chemical analysis required to identify the problem.
Advantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
Disadvantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
- Does not indicate the primary cause of the deficiency problem.
- Does not indicate the primary cause of the deficiency problem.
Disadvantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
- It has problem in identifying what is really the problem; is it low in supply or poor assimilation?
Disadvantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
- Does not indicate the amount needed to correct the limiting element.
Disadvantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
- Deficiency can be relative to deficiency of one nutrient may be related to an excessive quantity of another or very low level of one can induce poor absorption or utilization of other elements.
Disadvantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
- Hidden Hunger can occur and may cause misinterpretation of nutritional status.
Disadvantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
- Many nutrients have chlorosis symptoms and these can overlap in advanced growth stages if not diagnosed early enough.
Disadvantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
- It is difficult to distinguish among the deficiency symptoms in the field because disease or insects damage resemble certain micronutrient deficiencies.
Disadvantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
- May be too late to correct the problem when the deficiency appears.
Disadvantages of Using Nutrient Deficiency Symptoms in Soil Fertility Evaluation:
determination of the nutrient content of a plant part or whole plant sampled at a specific stage of growth.
Plant Analysis
Principle: As more of a nutrient is applied or is present in the medium, the nutrient concentration in the plant increases as the yield increases up to a given point.
Plant Analysis
The total amount in the plant is a function of the available supply from the soil.
Plant Analysis
Premise: amount of given element in a plant is an indication of the supply of that
particular nutrient and as such is directly related to the quantity in the soil.
Plant Analysis
Two General Types of Plant Analysis:
- Tissue Test- done on fresh plant tissue, in the field.
- Total Analysis- done in laboratory using precise analytical techniques.
● rapid test for determination of nutrient elements in plant sap of fresh tissue.
● sap from ruptured cells tested or unassimilated N, P, and K.
● semi-quantitative test intended for verifying or predicting deficiencies of N, P, and K.
Tissue Test
● plant parts to be tested in tissue test:
● in general, conducive tissue of the latest mature leaf is used for
testing.
● immature leaves at top of plant crop are avoided.
● laboratory determination of total elemental content of plants or of certain plant parts, using precise analytical techniques.
● used for: monitoring the nutrient status of crops and diagnose existing nutrient problems. Serve as basis for nutrient recommendations for
perennial fruit crops.
Total Analysis
this involves drying, grounding, and ashing of plant samples.
● many elements can be determined simultaneously.
● use of ICP optical emission spectrometry; flame atomic absorption spectrometry.
● plant parts to sample are recently matured materials (leaves).
Total Analysis
in total plant analysis the following method can be done in determining each element:
- Vanadomolybdate Method
total phosphorus
in total plant analysis the following method can be done in determining each element:
- Flame Photometer Method using Solution B or
Ammonium Oxalate Extract
total potassium
in total plant analysis the following method can be done in determining each element:
- Ethylenediaminetetraacetic Acid (EDTA) Method
total calcium
in total plant analysis the following method can be done in determining each element:
-Titration of Calcium plus Magnesium with EDTA
total magnesium
in total plant analysis the following method can be done in determining each element:
- Kjeldahl Method
total nitrogen
● Indicates the end result of absorption as affected by factors of availability existing in the location or environment.
● Provides direct measure of the nutrient status of the plant that is affected by the availability of the nutrients in the soil.
Total Analysis- Advantages
● Needs more complex calibration of analytical test values; consider the
age of plant, and cultivar.
● Expensive; requires laboratory equipment.
● Concentration easily affected by environmental conditions such as drought, rainfall and drainage.
● Shortage of one element may cause other elements to accumulate or it may result in poor utilization of other elements resulting in increased concentration.
● Postmortem analysis.
Disadvantage: Total Analysis
This method includes:
● field experiment
● pot experimentation
● microbiological test
Biological Test
● comparison of several treatments of fertilizer, lime, etc., including a control to answer specific questions under field condition.
Field Experiment
Principles: comparison of plant growth rate at different treatments or levels of the selected factor under actual field condition better reflects the influence of the environment.
Field Experiment
