This document discusses different types of biological tests used to evaluate soil nutrients and fertilizer treatments, including field experiments, pot experiments, and microbiological tests. Field experiments compare plant growth under different fertilizer or soil treatments under actual field conditions. Pot experiments similarly compare treatments but under more controlled artificial conditions. Microbiological tests use microorganisms like Azotobacter and Aspergillus niger to determine soil nutrient levels by measuring their growth response. The document also defines different types of fertilizers and fertilizer terminology.

1. Biological Tests
• Field Experiment
• comparison of several treatments
of fertilizer, lime, etc., including a
control to answer specific
questions under field condition.
• 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.
• Plants are harvested after a
uniform time interval, usually at
the end of the growing season
• Microbiological Test
• use of microorganism to determine
the presence of nutrients in the soil:
Azotobacter or Aspergillus niger
reflects nutrient deficiency in the soil.
• Azotobacter and Aspergillus niger
were used to determined phosphorus
and potassium.
• Small amounts of soil are incubated
for a period of four days in flask
containing the appropriate nutrient
solutions. The weight of the mycelial
par or the amount of potassium
absorbed by these pads is used as a
measure of the nutrient deficiency.

2. Biological Tests
• Pot Experiment
• comparison of several
fertilizer treatments
including a control
using small amount of
soil in pots to have
better control of
environmental factors.
• under artificial
conditions.
• Soil in pot; short
duration; preliminary in
nature
• Sunflower test for
boron
• Minus One Element Technique
• developed by Dr. Cesar P. Mamaril in PhilRice
• compares pots with one missing element to a
pot with complete N, P, K, S, Zn, Cu; most
common nutrient deficiencies associated with
lowland rice soils

3. Fertilizer
• Fertilizer – any substance that is added to the soil to supply the plants with one or
more elements
• Inorganic fertilizers – it has definite chemical composition; man made
• Organic fertilizer – fertilizer materials of organic origin
• Fertilizer element – macro or micronutrient supplied by a fert material (ex. N, P, K)
• Fertilizer nutrient – available or soluble form of fertilizer element (ex. P205, K20)
• Fertilizer material – organic or inorganic material used as fertilizer (ex. Urea, guano)
• Fertilizer grade – percent nutrient in a fert material (Ammophos: 16% N, 20% P2O5)
• Fertilizer ratio – relative proportion of nutrients in lowest term (T14 1:1:1)
• Fertilizer recommendation – expressed in either wt of fertilizer material or wt of
fert nutrient per ha basis (ex. 2 bags MOP per ha., 120 N-90 P2O5-60K2O/ha)

4. Fertilizer
• Single/straight fertilizer –carries only one element
• Compound fertilizer –it carries two elements
• Complete fertilizer – it contains all the three basic (primary) elements. N P K)
• Mixed fertilizer – it contains several elements and the source of elements can
not be identified, achemical or mechanical combination of two or more
fertilizers