This document summarizes key edaphic, or soil-related, factors. It defines edaphic factors as abiotic soil components like temperature, pH, and mineral composition. Soil is described as the biologically active upper layer of Earth's crust that serves as a habitat and nutrient reservoir. Soil properties like texture, structure, temperature, moisture, organic matter, nutrients, and cation exchange capacity are explained in relation to the types of organisms that can inhabit different soils. Methods for analyzing soil temperature, pH, moisture, organic matter, calcium, nitrogen, and phosphorus levels in the field are also outlined.

1. Edaphic Factors

2. Edaphic factor
• Gk ‘edaphos’= ground, soil
• Abiotic factor
• Relating to the physical or chemical components of
the soil found in a particular area
– Temperature
– pH
– Mineral composition

3. Soil
• The biologically active, porous medium that has
developed in the uppermost layer of the Earth's
crust.
• Natural reservoir of water and nutrients
• Medium for the filtration and breakdown of
injurious wastes
• Foundation of all terrestrial ecosystems.
– Habitat of billions of plants, animals, and
microorganisms that take part in the cycling of nutrients

4. Soil
• Evolved through the weathering of solid materials. The
bulk of soil consists of mineral particles composed of
silicate ions combined with various metal ions.

5. Soil Profile
• Texturally distinct
layers or horizons
• Different for every area

6. Soil Classification Map

9. Tropical climate

10. Soil Temperature
Color
• Dark soil absorbs more energy than light colored
soil.
Slope
• Greater absorption can be observed as the angle of
incidence of the sun's rays approaches
perpendicular to the soil surface.
Vegetative cover of the soil
• Bare soil warms and cools faster than soil with
vegetation.

11. Importance of Temperature
• Heat is the catalyst for many biological
processes.
• Soil temperature is primarily important in
growing plants.

12. Soil pH
• Soil pH greatly influences nutrient availability and
solubility in plants.
– Acidic soils are often low in nutrient concentrations.
• Soil pH also determines the presence of different
microorganisms
• An indicator of corrosiveness of the soil.

13. Factors affecting soil pH
• pH of the soil can be affected by different
factors such as:
– mineral content of the soil
– climate
– weathering
– properties of rainfall
– induced fertilizers

14. Soil Moisture
• Water that is held in the spaces between soil
particles
• Related to water-holding capacity of the soil
and heat-capacity of soil

15. Organic Matter
• Serves as the “revolving nutrient bank account”
• Serves as a reserve for many essential nutrients,
especially nitrogen
• Serves as an agent to improve soil fertility and hold
important plant nutrients e.g. by adding organic
matter to sandy soil, the ability of the soil to retain
water increases

16. Organic Matter
• Organic matter is related to soil color
– The darker the soil, the more organic matter

17. Soil Nutrients
• Nutrients are required for plants to grow and
develop.
• Low nutrient levels result in stunted growth, low
flowering and fruit production
• Can be supplied by the addition of fertilizers
(inorganic or organic)
• Two categories:
– Macronutrients
• Primary nutrients - NPK
• Secondary nutrients – Ca, Mg, S
– Micronutrients (B, Cu, Fe, Cl, Mg, Mo, Zn)

18. Calcium
• Secondary macronutrient
• Construction of cell walls and proper
functioning of growing tissue
• Calcium deficiency: extremely acidic soil
• Necrosis around the base of the leaves

19. Nitrogen
• Primary Macronutrient
• Green leaf growth  chlorophyll
• Nitrogen deficiency
– Stunted growth
– Pale green and yellow leaves

20. Phosphorus
• Primary macronutrient, mobile
• Cell development, promotion of good root growth,
flowering, fruiting, and ripening
• ATP component, biomolecules  NA, phospholipids
• Limited in most soils because it is release vey slowly from
insoluble phosphates
• Phosphorus deficiency
– Intense green color, Poor root development
– Purplish leaves  abnormal increase in sugar content &
anthocyanin

21. Soil Texture
• Used to designate the
proportionate distribution of
the different sizes of mineral
particles in a soil

22. Soil Pyramid
40% sand + 40% silt + 20 clay = loam
10% sand + 45% silt + 45% clay = ?
55% sand + 15% silt + 30% clay = ?

23. Soil particle size classification
USDA System ISSS System
Category Size (mm) Category Size (mm)
Clay <0.002 Clay <0.002
Silt 0.002-0.05 Silt 0.002-0.02
Very fine sand 0.05-0.10
Fine sand 0.10-0.25 Fine sand 0.02-0.2
Medium sand 0.25-0.5
Coarse sand 0.5-1.0 Coarse sand 0.2-2
Very coarse sand 1.0-2.0
USDA – US Dept. of Agriculture
ISSS – International Soil Science Society
Milne et al. 1991. Soil Description Handbook. DSR. Land Resources. Lower Hutt

24. Soil particle size classification
For large particles (Milne et al. 1991)
Category Size (mm)
Fine gravel 2-6
Medium gravel 6-20
Coarse gravel 20-60
Very coarse gravel 60-200
Boulders >200
USDA – US Dept of Agriculture
ISSS – International Soil Science Society
Milne et al. 1991. Soil Description Handbook. DSR. Land Resources. Lower Hutt

25. Soil Structure
• Refers to the grouping of soil particles into porous
compounds; arrangement of aggregates into larger clumps
• Influenced by soil texture
• Types of aggregate arrangements:
– Granular
– Blocky
– Prismatic
– Columnar
– Platy
– Singly grained

26. Types of Soil Structure
• Granular – resembles cookie crumbs; usually less than 0.5 cm in
diameter; commonly found in surface horizons where roots have been
growing
• Blocky – irregular blocks that are usually 1.5 – 5.0 cm in diameter
• Prismatic – vertical columns of soil; usually found in lower horizons
Granular Blocky Prismatic

27. Types of Soil Structure
• Columnar – vertical columns of soil having salt ‘caps’ at the top; found
in soils of arid climates
• Platy – thin, flat plates that lie horizontally; usually found in compacted
soil
• Single grained – soil is broken into individual particles that do not stick
together; loose consistency; commonly found in sandy soils
Columnar Platy Singly grained

28. The size and shape of clumps affect the capacity of soil to hold water, air, and nutrients.
GRANULAR PLATYBLOCKY

29. Field Capacity
• Maximum amount of water that a particular soil
can hold
• Water exists in soil capillaries; pores small enough
to hold water against gravity
• Soil texture
– Field capacity will be reached faster in coarser textured
soil (loamy soil) than fine-textured soil profiles (clay)
• Soil structure
– Amount of aggregation determines the amount of
pores available to hold water

30. • Since forces holding water are surface-attractive
forces, the more surface area a soil has, the greater
is the amount of water adsorbed.
• Field capacity comparisons
– SAND: LOWER FIELD CAPACITY lower surface area, large
pores  favor rapid water infiltration and drainage
– CLAY: HIGHER FIELD CAPACITY, higher SA, small pores
 greater active surface for adhesion of water
molecules.
Field Capacity

31. Cation-Exchange Capacity (CEC)
• Ability of the soil particles to adsorb and exchange cations
that are loosely bound to its surface
• Measure of how many negatively-charged sites are
avaialble in the soil
• Highly dependent on soil texture and OM content
– More clay, more OM  higher CEC
– Clay
• weakly (-) charged: higher affinity to cations
• higher surface area exposed
– Organic matter
• has both (+) and (-) sites

32. Cation-Exchange Capacity
• Measure of fertility, nutrient retention capacity,
and the capacity to protect groundwater from
cation contamination
• Ideally, CEC for agricultural soils is between 10 and
30 meq*/100g (sandy loam- loam)
– Higher CEC – more clay
– Lower CEC – more sand
* Milliequivalentstakes into account both the weight and the charge of the cation

33. Determine the following parameters:
• Temperature
• pH
• Soil moisture
• Amount of organic matter
• Presence of nutrients (calcium, nitrates, phosphorus)
• Soil texture
• Soil inhabitants
Act. 2: Edaphic factors and the soil inhabitants

34. Act. 2: Edaphic factors and the soil inhabitants
1. Examine important ecological properties of soil.
2. Compare soil characteristics in various habitats.
3. Determine what organisms live within the soil
medium as well as their adaptation, abundance,
and over-all ecology.

35. Soil Profile
Dig at least 1 ft. below the ground
Collect soil samples in each major soil horizons
Take note the differences in color, structure, and
thickness within the major horizons

36. Soil Temperature
Equilibrate thermometer for two minutes
Bury thermometer 3-6 inches below the ground and take 5 readings.
Determine the soil temperature profile by plotting the soil temperature on the horizontal axis
and the depth of the soil on the vertical axis

37. Soil pH
Mix soil and distilled water in equal amounts
(1:5 dilution; 10g with 50mL of water)
Allow soil particles to settle until a clear supernate forms
Take soil pH using a pH meter

38. Soil Moisture
Oven dry 10g of soil placed in a pre-weighed crucible
(105ºC for 24 hours)
Allow to cool in a dessicator. Weigh.
The dry weight sample is computed as the weight of the
container with the oven-dried sample minus the weight of the
container alone: (Wd = Wo – Wc)

39. Calculations
Amount water = Fresh weight – Dry weight
% water in sample =
Fresh weight – Dry weight
____________________________
Fresh weight
X 100

40. Soil Organic Matter
Take 1-5 g oven-dried sample and place onto a pre-weighed
crucible (Wc). Weigh (Wo).
Heat in a furnace at 450ºC overnight. Cool. Weigh. (Wi)
weight of the ignited soil sample (Wi – Wc).
organic matter content (Wo – Wi), % of dry weight of the
sample.

41. Calcium Test
Combine 10 drops of soil supernate + 10 drops of 5g
ammonium oxalate solution in 100mL distilled water
Shake vigorously. Observe after 5 minutes.
POSITIVE: milky-white precipitate
NEGATIVE: no color change

42. Calcium Test
Add soil and 10% HCl in a
crucible
POSITIVE:
Effervescence. Amount
is estimated using a
table of determination
of % CaCO3
Effervescence  carbon dioxide in the atmosphere
Higher calcium carbonate present, the louder effervescence

43. % CaCO3 Audible Effect Visible Effect
< 0.1 None None
0.5 Faint None
1.0 Faint-moderate Barely visible
2.0
Distinct
Heard away from ear
Visible from very close
5.0 Easily heard Bubbles up to 3 mm easily seen
10.0 Easily heard
Strong effervescence
With bubbles of 7 mm
(After Clarke, 1957)
Determination of % CaCO3 in soil sample

44. Nitrate Test
Combine 10 drops of soil supernate + 10
drops of solution (0.33g diphenylamine
in 25mL H2SO4) in a test tube
Shake vigorously. Observe after 5
minutes.
POSITIVE: brown - blue color

45. Phosphorus Test
Combine 10 drops of soil supernate + 10 drops of
solution (5g ammonium molybdate, 50mL distilled
water and 50mL concentrated HNO3) in a test tube
Add a piece of tin. Shake. Observe after 5 minutes
POSITIVE: gray to deep blue coloration

46. Field Key To Soil Texture
SAND
LOAMY SAND
LOAM
SANDY LOAM
SILT LOAM
CLAY LOAM
SANDY CLAY LOAM
SILTY CLAY LOAM
SILT
CLAY
SANDY CLAY
SILTY CLAY
Preliminary
• Feeling the soil  grainy or sticky
•Sandy or clayish, may color hand
Moisten 10-15cm soil. Knead and try to
mold into a ball.
Follow key to make a rough
classification.

47. Soil Inhabitants
Collect litter in the site and place in a plastic bag.
Add few drops of chloroform / ether. Wait for 5
minutes.
Empty the contents in a white paper and look for soil
invertebrates. Preserve in a small jar of alcohol or
formalin.

48. Soil Inhabitants
Place the collected soil sample in the Berlese-Tulgren
apparatus.
Observe for any organisms that will fall in the
receptacle. Identify. Leave for 2 days.
Continue observation and identification of soil
invertebrates.

49. Berlese-Tulgren apparatus
• Made up of a light bulb,
aluminum foil funnel, gauze,
and a test tube with formalin.
• The organisms were forced to
crawl downward because of
the heat and light from the
bulb.
– Light heats and dries soil
– Positive geotaxis in response
to dryness

50. Berlese-Tulgren apparatus
• Limitation: Biased sample of soil fauna
– Based on specific avoidance behavior triggered
by dryness
– Best captures mobile animals and those that do
not dessicate easily
– Immobile larvae, endophagous nymphs and soft-
bodied invertebrates such as nematodes  not
extracted by a Berlese funnel.

51. Area designation
Group Area
1 and 6 Lagoon
2 and 7 Old G. Silang Building
3 and 8 Water tank / Sining Lahi Headquarters
4 and 9 Gym / PE building
5 and 10 Oval