The document discusses soil fertility evaluation and nutrient assessment techniques. It describes how plant nutrient needs vary based on species, yield, soil properties, environment and management. Several assessment methods are outlined, including visual deficiency symptoms, plant tissue analysis, greenhouse and field tests, and soil testing. Plant tissue analysis involves tests on fresh or dried tissue to diagnose nutrient needs and quantify crop responses. Greenhouse and field tests are used to verify nutrient recommendations. The objectives of soil testing are to predict available nutrients and provide a basis for fertilizer recommendations.

1. SOIL SCIENCE
FPT 2093
Lecture Week 14:
Soil Fertility Evaluation
En Mohd Fauzie Jusoh
Lecturer
Agrotechnology Programme
Faculty of Agro-Based Industry
Universiti Malaysia Kelantan (Jeli Campus)
Locked Bag No.100, 17600 Jeli, Kelantan.
014-2903025/fauzie.j@umk.edu.my/

2. Introduction
Optimum plant health and productivity of a cropping system
depends on an adequate supply of plant nutrients. The quantity of
nutrients required by plants varies depending on:
• plant species and variety
• yield potential
• soil properties
• environment
• Management
Knowing the relationship between test results and crop nutrient
response is essential for providing an accurate nutrient
recommendation. Several techniques are commonly employed to
assess the nutrient status of a soil:
• nutrient-deficiency symptoms of plants
• tissue analysis of plants growing on the soil
• remote sensing
• soil analysis

3. Plant Nutrient-Deficiency Symptoms
Each visual symptom is related to a nutrient function in the
plant.
Most nutrients have several functions, making it difficult to
identify the reason for a particular deficiency symptom.
Understanding nutrient mobility in the plant is important to
accurately identify a specific nutrient-deficiency symptom.
In addition to leaf symptoms, nutrient deficiencies have a
marked effect on root growth.
Visual deficiency symptoms can be related to factors other than
nutrient stress.

4. Plant Nutrient-Deficiency Symptoms

5. Plant Nutrient-Deficiency Symptoms
Nutrient-deficiency symptoms appear when nutrient supply is
so low that the plant cannot function properly.
Nutrient-deficiency symptoms appearing during early growth
may disappear as the growing season progresses, or there
may be no measurable yield benefit.
With cooler temperatures, nutrient uptake is reduced
because:
• mass flow of nutrients is reduced by decreased growth rate and
transpiration
• diffusion rate decreases with declining temperature and a lower
concentration gradient
• Mineralization of organic bound nutrients is reduced

6. Plant Analysis
Plant analysis methods include tests on fresh tissue in the
field and analyses performed in a laboratory. Plant analyses
are performed to:
• verify the accuracy of an assessment of visual deficiency
symptoms
• identify plant nutrient shortages before they appear as symptoms
• help in determining the relative nutrient-supplying capacity of the
soil
• quantify the effect of nutrient addition on nutrient concentration
in the plant
• study the relationship between plant nutrient status and crop
performance (i.e., yield)

7. Plant Analysis
• Tissue Tests
Nutrient analysis on fresh tissue is important in
diagnosing nutrient needs of growing plants.
Application of nutrients to correct a nutrient stress
identified with a tissue test may not be feasible
because:
• the deficiency may have already caused yield loss
• the crop may not respond to the applied nutrient at the specific
growth stage tested
• the crop may be too large to apply nutrients
• climatic conditions may be unfavorable for fertilization

8. Plant Analysis
• Tissue Tests (cont.)
Cell Sap Tests
Semiquantitative estimates of plant N, P, and K can be rapidly obtained
with simple plant tissue tests conducted in the field. Plant leaves or
stems are chopped up and extracted with reagents specific for each
nutrient. Plant tissue can also be squeezed with a garlic press to
transfer plant sap to filter paper and color-developing reagents are
then added. The color intensity of the cell sap/reagent mix is
compared with a standard chart that indicates very low, low,
medium, or high nutrient content.

9. Plant Analysis
• Tissue Tests (cont.)
Total Analysis
Total analysis is performed on specific plant parts (e.g., petioles,
stems, leaves) in a laboratory. After sampling, plant material is
dried, ground, and nutrient content determined following wet
digestion with concentrated acid or dry ashing in a high-
temperature oven. As in tissue tests, the plant part selected is
important, with the most recently matured leaf preferred.
Samples should be kept dry or refrigerated and protected from
contamination.

10. Plant Analysis
• Tissue Tests (cont.)
Sampling Time
Growth stage is important in plant analysis because
nutrient status and demand vary during the season.
Nutrient concentration
in vegetative parts
usually decreases
with maturity.
Misinterpretation of
plant analysis results
are common if
sampling time is not
identified correctly.
Deficient
Adequate
CNR

11. Greenhouse and Field Tests
• Greenhouse Tests
Simple greenhouse tests involve growing plants in
small amounts of soil collected from a field suspected
of being nutrient deficient to assess nutrient availability.

12. Field Tests
• Strip Tests
Narrow field strips where selected nutrient treatments have been
applied
can help verify the
accuracy of nutrient
recommendations.
The test results
must be interpreted
with caution if they
are unreplicated.
Replication of strip
tests on several
farms is also
helpful.

13. Greenhouse and Field Tests
• Field Tests
Measuring crop response to applied nutrients is commonly done by
agricultural scientists developing nutrient recommendations. After
treatments are selected, they are randomly assigned to an area of land.
The treatments are replicated to obtain more reliable results and to
account for soil variations at the experimental site.

14. Soil Testing
• Objectives of Soil Tests
Soil test information can be used to:
• provide an index of nutrient availability in soil. The soil test or extractant
is designed to extract a portion of the nutrient from the same “pool” (i.e.,
solution, exchange, organic, or mineral) used by the plant
• predict the probability of obtaining a profitable response to fertilizer or
lime. Although a response to applied nutrients will not always be obtained
on low-testing soils because of other limiting factors, the probability of a
response is greater on low-testing soils.
• provide a basis for development of fertilizer and lime recommendations.
The basis for nutrient recommendations relies on detailed laboratory,
greenhouse, and field studies.

15. Soil Testing
• Objectives of Soil Tests (cont.)
– The objective of soil testing is to simply help predict
the amount of nutrients needed to supplement native
soil nutrient supply.
– The soil testing-nutrient recommendation system is
comprised of four consecutive steps:
1. Collect a representative soil sample from the field.
2. Determine the quantity of plant available nutrient in the soil sample
(soil test).
3. Interpret the soil test results (soil test calibration).
4. Estimate the quantity of nutrient required by the crop (nutrient
recommendation).

16. Soil Testing
• Nutrient Recommendations
Nutrient Mobility: Soil test interpretation for purposes of making
nutrient recommendations is influenced by the mobility of the
nutrient.
Mobile Nutrient Recommendations: With mobile nutrients, soil test
buildup and/or maintenance programs are not viable, because these
nutrients are readily mobile in the root zone in many soils.
Immobile Nutrient Recommendations: With immobile nutrients, crop
yield potential is limited by the quantity of nutrient available at the
soil-root interface. Generally, solution concentrations of immobile
nutrients are low, and replenishment occurs through exchange,
mineralization, and mineral solubility reactions.

17. Questions…
Thank You