Soil quality is considered as the capacity of a soil to function. Two types - Inherent & Dynamic Qualities. Assessment of soil quality. Selevtioof parameter. Physical Chemical and Biological parameters

2. SoilQuality
• Soil quality is considered as the capacity of a soil to
function.
• Soil quality is defined by the interactions of a particular
soil’s measurable chemical, physical, and microbiological
properties.
• According to Committee for the Soil Science Society of
America (Karlen et al., 1997) “it is the capacity of a specific
kind of soil to function, within natural or managed
ecosystem boundaries, to sustain plant and animal
productivity, maintain or enhance water and air quality, and
support human health and habitation”.

3. SoilQuality–2types
Soil has both Inherent & Dynamic Qualities
• Inherent soil quality: soil’s natural ability to function.
For eg: sandy soil drains faster than a clayey one. Deep
soil has more room for roots than soils with bedrock near
the surface.
• These characteristics are permanent .
• The inherent quality of soils is often used to compare the
abilities of one soil against another, and to evaluate the value
or suitability of soils for specific uses.

4. • Dynamic soil quality: is how soil changes depending on
how it is managed.
• Management choices affect the amount of soil organic
matter, soil structure, and water- and nutrient-holding
capacity.
• One goal of soil-quality research is to learn how to
manage soil in a way that improves its functions. This
dynamic aspect of soil quality is the focal point of
assessing and maintaining healthy soil resources.

5. Whyassesssoilquality?
 To learn how to manage soil in a way that improves its
functions.
 To achieve the environmental sustainability
 Awareness and education
 Evaluation of practice effects and trouble-shooting
 Evaluation of alternative practices

6. SoilQualityAssessment
• 2 main questions to be answered :
(i) how does the soil function
(ii) what procedures are appropriate for making the evaluation.
• After answering those questions,
a range of parameter values or indexes that indicate a soil is
functioning at full potential can be calculated
using landscape characteristics, knowledge of pedogenesis, and a
more complete understanding of the dynamic processes occurring
within a soil.

7. SoilQualityParameter
• A soil-quality parameter is a simple attribute of the soil
which may be measured to assess its quality with respect
to a given function.
• It is important to be able to select attributes that are
appropriate for the task, given the complex nature of the
soil and the exceptionally large number of soil parameters
that may be determined.

8. IdealParametersshould:
 correlate well with ecosystem processes
 integrate soil physical, chemical, and biological
properties & processes
 be accessible to many users
 be sensitive to management & climate
 be components of existing databases
 be interpretable

9. Soil Quality Parameters – 3 groups
• physical, chemical, or biological indicators
• Many of the physical and chemical soil attributes are
permanent in time (inherent parameters).
• In contrast, biological and some physical attributes are
dynamic and exceptionally sensitive to changes in soil
conditions and in management practices(dynamic
parameters).

10. The Selection Of Parameters
Should be based on:
(i) land use
(ii) Soil function
(iii) reliability of measurement
(iv) spatial and temporal variability
(v) sensitivity to changes in soil management
(vi) comparability in monitoring systems
(vii) skills required for the use and interpretation

11. Physical parameters
• Physical indicators provide
information about soil hydrologic
characteristics, such as water
entry and retention, that
influences availability to plants.
• Some indicators are related to
nutrient availability by their
influence on rooting volume and
aeration status.
Physical parameters
• Soil texture
• Stoniness
• Soil structure
• Bulk density
• Porosity
• Aggregate strength & stability
• Soil crusting
• Soil compaction
• Water retention
• Drainage
• Infiltration
• Hydraulic conductivity
• Topsoil depth

12. Chemical parameters
Chemical indicators can give you
information about the
• equilibrium between soil solution
and exchange sites
• plant health
• the nutritional requirements of
plant and soil animal
communities
• and levels of soil contaminants
and their availability for uptake
by animals and plants.
Chemical parameters
• Color
• pH
• Carbonate content
• Salinity
• Sodium saturation
• Cation exchange capacity
• Plant nutrients
• Toxic elements

13. Biological parameters
• Biological indicators can tell us
about the organisms that form the
soil food web that are responsible
for decomposition of organic
matter and nutrient cycling.
• Information about the numbers of
organisms, both individuals and
species, that perform similar jobs
or niches, can indicate a soil's
ability to function or bounce back
after disturbance (resistance and
resilience).
Biological parameters
• Organic matter content
• Populations of organisms
• Fractions of organic matter
• Microbial biomass
• Respiration rate
• Mycorrhizal associations
• Nematode communities
• Enzyme activities
• Fatty acid profiles
• Bioavailability of contaminants

14. A minimal dataset to characterize soil
quality.
• Typical soil tests only look at chemical indicators.
Or consider,
• 7 Physical
• 3 Chemical &
• 2 Biological parameters

15. Organic matter
• Organic matter/ soil carbon, transcends all three indicator
categories
• Has the most widely recognized influence on soil quality.
• Organic matter is tied to all soil functions.
• It affects other indicators, such as aggregate stability
(physical), nutrient retention and availability (chemical), and
nutrient cycling (biological)
• Is itself an indicator of soil quality.

16. Earthworms
• Classified into 3 groups based on their habitat : litter-dwellers , mineral soil-dwellers , deep
soil-burrowers.
• Earthworm cast is digested material that is excreted back into the soil. Cast is enriched with
nutrients (N, P, K, and ca) and microorganisms during its passage through the worm’s digestive
system.
• Fresh cast is a site of intense microbial activity and nutrient cycling.
• Contribute nutrients to the soil and improve porosity, and root development. They are
measured in number/m2.
• Contribute to crop production.
• Play a key role in modifying the physical structure of soils by producing new aggregates
and pores, which improves soil tilth, aeration, infiltration, and drainage.
• Produce binding agents responsible for the formation of water-stable macro-aggregates
• They improve soil porosity by burrowing and mixing soil.
• stimulate root growth and proliferation deep into the soil to satisfy nutrient and water
requirements.
• Low or absent earthworm populations are an indicator of little or no organic residues in the
soil and/or high soil temperature and low soil moisture that are stressful not only to earthworms,
but also for sustainable crop production.

17. Respiration rates
• Carbon dioxide (CO2) release from the soil surface is referred to as soil respiration. This CO2 results
from aerobic microbial decomposition of soil organic matter (SOM) to obtain energy for their growth
and functioning (microbial respiration), plant root and faunal respiration, and eventually from the
dissolution of carbonates in soil solution. Soil respiration is one measure of biological activity and
decomposition.
• The rate of CO2 release is expressed as CO2-C lbs/acre/day
• During the decomposition of SOM, organic nutrients contained in organic matter (e.g., organic
phosphorus, nitrogen, and sulfur) are converted to inorganic forms that are available for plant uptake
(mineralization).
• Soil respiration reflects the capacity of soil to support soil life including crops, soil animals, and
microorganisms.
• It describes the level of microbial activity, SOM content and its decomposition.
• Reduced soil respiration rates signify that soil properties that contribute to soil respiration (soil
temperature, moisture, aeration, available N) are limiting biological activity and SOM decomposition.

19. • The % CO2 reading
should be an estimate
of the highest point that
the purple color can be
easily detected.

20. Soil Enzymes
• Soil enzymes increase the reaction rate at which plant residues decompose and release plant
available nutrients.
• Sources of soil enzymes include living and dead microbes, plant roots and residues, and soil
animals.
• Enzymes stabilized in the soil matrix accumulate or form complexes with organic matter (humus),
clay, and humus-clay complexes, but are no longer associated with viable cells.
• It is thought that 40 to 60% of enzyme activity can come from stabilized enzymes, so activity does
not necessarily correlate highly with microbial biomass or respiration.
• Therefore, enzyme activity is the cumulative effect of long term microbial activity and activity of
the viable population at sampling
• Enzymes respond to soil management changes long before other soil quality indicator changes are
detectable.
• Soil enzymes play an important role in organic matter decomposition and nutrient cycling
• Some enzymes only facilitate the breakdown of organic matter (e.g., hydrolase, glucosidase),
while others are involved in nutrient mineralization (e.g., amidase, urease, phosphatase, sulfates).

21. Soil pH
• Soil pH generally refers to the degree of soil acidity or alkalinity.
• The pH scale ranges from 0 to 14; a pH of 7 is considered neutral. If pH values are
greater than 7, the solution is considered basic or alkaline; if they are below 7, the
solution is acidic.
• Soil pH affects the soil's physical, chemical, and biological properties and processes,
as well as plant growth. The nutrition, growth, and yields of most crops decrease
where pH is low and increase as pH rises to an optimum level
• Many crops grow best if pH is close to neutral (pH 6 to 7.5) although a few crops
prefer acid or alkaline soils. In acid soils, calcium and magnesium, nitrate-nitrogen,
phosphorus, boron, and molybdenum are deficient, whereas aluminum and
manganese are abundant, sometimes at levels toxic to some plants.
• Phosphorus, iron, copper, zinc, and boron are frequently deficient in very alkaline
soils. Bacterial populations and activity decline at low pH levels, whereas fungi adapt
to a large range of pH (acidic and alkaline). Most microorganisms have an optimum pH
range for survival and function

22. Electrical Conductivity
• The electrical conductivity (EC) of soil-water mixtures indicates the amount of salts present in
the soil.
• All soils contain some salts, which are essential for plant growth.
• However, excess salts will hinder plant growth by affecting the soil-water balance.
• Soils containing excess salts occur both naturally and as a result of soil use and management.
• Salt-affected soils are largely found in the western arid and semiarid areas of the country,
where the annual rainfall is low, allowing salts to accumulate in the soil profile.
• The electrical conductivity measurement detects the amount of cations or anions (salts) in
solution; the greater the amount of anions or cations, the greater the electrical conductivity
reading.

23. EC – Test Method
• Add 1/8-cup (30 mL) of distilled water to the container with
the subsample.
• The resulting soil/water mixture equates to a
• 1:1 soil to water ratio on a volume basis.
• Put the lid on the container and shake
• vigorously about 25 times.
• Open the container and insert the EC pocket meter into the
soil-water mixture.
• Take the reading while the soil particles are still suspended
in solution.
• To keep the soil particles from settling, stir gently with the
EC pocket meter.

24. NITRATE
• The amount of residual nitrate-N in the soil at any one time is a function of the rate at which
microorganisms decompose soil organic matter .
• This rate is dependent on temperature, moisture, aeration, type of organic residues, pH, and other
factors (Dahnke and Johnson, 1990).
• Also, once soil nitrate has formed, it is subject to leaching, fixation, denitrification, and plant uptake
.Therefore, it is difficult to interpret the nitrate-N content
• useful in determining fertilizer-N needs of crops in certain regions during specific times of the year
and at specific crop growth stages (Dahnke and Johnson, 1996).
• Any amount of nitrate in the soil that is not used by the crop may potentially be leached from the
root zone and become an environmental liability.
• Nitrate is not adsorbed on to soil particles unless they have a positive charge. Therefore, nitrate can
readily move with percolating water out of the root zone and into groundwater or into surface
waters through subsurface flow .
• Acidic soils of the humid tropics contain a significant amount of positively charged soil particles
which can hold nitrate and keep it from leaching.

26. • The downward entry of water into the soil.
• The velocity at which water enters the soil is infiltration
rate.
• Expressed in inches per hour.
• Indicator of the soil’s ability to allow water movement
into and through the soil profile.
• When water is supplied at a rate that exceeds the soil’s
infiltration capacity, it moves downslope as runoff on
sloping land or ponds on the surface of level land.

27. • When runoff occurs on bare or poorly vegetated soil, erosion takes place. Runoff carries
nutrients, chemicals, and soil with it, resulting in decreased soil productivity, off-site
sedimentation of water bodies and diminished water quality. Sedimentation decreases
storage capacity of reservoirs and streams and can lead to flooding.
• Restricted infiltration and ponding of water on the soil surface results in poor soil aeration,
which leads to poor root function and plant growth, as well as reduced nutrient availability
and cycling by soil organisms.
• Ponding and soil saturation decreases soil strength, destroys soil structure, increases
detachment of soil particles, and makes soil more erodible. On the soil surface rather than in
the soil profile, ponded water is subject to increased evaporation, which leads to decreased
water available for plant growth.
• A high infiltration rate is generally desirable for plant growth and the environment. In some
cases, soils that have unrestricted water movement through their profile can contribute to
environmental concerns if misapplied nutrients and chemicals reach groundwater and
surface water resources via subsurface flow.

29. • The amount of water in soil is based on rainfall amount, what proportion of rain
infiltrates into the soil, and the soil's storage capacity.
• Available water capacity is the maximum amount of plant available water a soil can
provide. It is an indicator of a soil’s ability to retain water and make it sufficiently
available for plant use.
• Water availability is an important indicator because plant growth and soil
biological activity depend on water for hydration and delivery of nutrients in
solution.
• Runoff and leaching volumes are also determined by storage capacity and pore
size distribution
• Available water capacity is used to develop water budgets, predict droughtiness,
design and operate irrigation systems, design drainage systems, protect water
resources, and predict yields.

30. • Bulk density is an indicator of soil compaction.
• It is calculated as the dry weight of soil divided by its volume.
• Bulk density is typically expressed in g/cm3.
• Bulk density reflects the soil’s ability to function for structural
support, water and solute movement, and soil aeration.
• Bulk densities above thresholds indicate impaired function .

31. • High bulk density is an indicator of low soil porosity and soil compaction.
• It may cause restrictions to root growth, and poor movement of air and water
through the soil.
• Compaction can result in shallow plant rooting and poor plant growth,
influencing crop yield and reducing vegetative cover available to protect soil
from erosion.
• By reducing water infiltration into the soil, compaction can lead to increased
runoff and erosion from sloping land or waterlogged soils in flatter areas.
• In general, some soil compaction to restrict water movement through the soil
profile is beneficial under arid conditions, but under humid conditions
compaction decreases yields

32. • Drive Ring into Soil
• Dig around the ring and with the trowel
underneath it, carefully lift it out to
prevent any
• loss of soil.
• Remove Excess Soil
• Weigh and Record Sample
• Extract Subsample to Determine Water
Content and Dry Soil Weight
• Weigh and Record Subsample
• Dry Subsample
• Weigh and Record Subsample

33. • are relatively thin, dense, somewhat continuous layers of non-aggregated soil particles on the
surface of tilled and exposed soils.
• Structural crusts develop when a sealed-over soil surface dries out after rainfall or irrigation.
• Water droplets striking soil aggregates and water flowing across soil breaks aggregates into
individual soil particles. Fine soil particles wash, settle into and block surface pores causing the
soil surface to seal over and preventing water from soaking into the soil. As the muddy soil
surface dries out, it crusts over.
• Structural crusts range from a few tenths to as thick as two inches. A surface crust is much
more compact, hard and brittle when dry than the soil immediately beneath it, which may be
loose and friable. Crusts can be described by their strength, or air-dry rupture resistance.
• A biological crust is a living community of lichen, cyanobacteria, algae, and moss growing on
the soil surface that bind the soil together. A precipitated, chemical crust can develop on soils
with high salt content.
• SURFACE CRUST indicates poor infiltration, a problematical seedbed, and reduced air
exchange between the soil and atmosphere. It can also indicate that a soil has a high sodium
content that increases soil dispersion when it is wetted by rainfall or irrigation.

34. • Crusts restrict seedling emergence, especially in non-grass crops such as soybeans and
alfalfa. Crusts can also reduce oxygen diffusion into the soil profile by as much as 50% if
the soil crust is wet.
• Surface sealing and crusts greatly reduce infiltration, and increase runoff and erosion.
• The sunlight (and energy) reflectance of a surface crust is higher than that of a non-
crusted soil, so soil temperature may be lower and surface evaporation reduced where
a crust exists
• This could negatively affect germination and development of healthy seedlings in cooler
climates.
• The relatively smooth surface of a crusted soil initially increases wind erosion of sandy
soils. Loose sand particles blow across and abrade the smooth surface of the crust.
Roughening of the surface crust eventually reduces wind erosion. For soils with a small
amount of sand, hard crusts protect the soil surface from wind erosion.
• Surface crusts can have other limited benefits. Crusts decrease water loss because less
of their surface area is exposed to the air compared to a tilled, fluffy soil. In addition, a
crust forms a barrier to evaporation of soil moisture. Reduced evaporation of soil
moisture means more water remains in the soil for plant use.

36. • Aggregate stability is a measure of the vulnerability of soil aggregates to
external destructive forces (Hillel, 1982).
• An aggregate consists of several soil particles bound together.
• Aggregates that stand up to the forces of water are called water stable
aggregates (WSA).
• the greater the percentage of stable aggregates, the less erodible the soil
will be.
• Soil aggregates are a product of the soil microbial community, the soil
organic and mineral components, the nature of the above-ground plant
community, and ecosystem history.
• They are important in the movement and storage of soil water and in soil
aeration, erosion, root development, and microbial community activity

37. • Sieve the Soil Sample
• Try to pass all of the soil through the sieve by
gently pressing the soil through with your
thumb
• Weigh the 0.25-mm sieve, and record its
weight on the Soil Data worksheet. Weigh out
about 10 g of the sieved soil from Step 1
• Place the 0.25-mm sieve containing the soil
on the wet cloth, allowing the soil to wet up
slowly
• Place the 0.25-mm sieve with soil in the
container filled with distilled water, so that
the water surface is just above the soil
sample.
• Move the sieve up and down in the water
through a vertical distance of 1.5 cm at the
rate of 30 oscillations per minute

38. • After wet sieving, set the sieve with aggregates on a
dry piece of terry cloth, which will absorb the
excess water from the aggregates in the sieve.
• place the sieve containing the aggregates on the
drying apparatus
• Weigh Aggregates
• Immerse the sieve containing the dried aggregates
in the calgon solution.
• Allow the aggregates in the sieve to soak for five
minutes, moving the sieve up and down
periodically. Only sand particles should remain on
the sieve.
• Rinse the sand on the sieve in clean water by
immersing the sieve in a bucket of water or by
running water through the sieve
• Dry and Weigh Sand

39. • Sand, silt and clay particles are the primary mineral building blocks of soil. Soil structure is the
combination or arrangement of primary soil particles into aggregates.
• Using aggregate size, shape and distinctness as the basis for classes, types and grades,
respectively,
• soil structure describes the manner in which soil particles are aggregated.
• Soil structure affects water and air movement through soil, greatly influencing soil's ability to
sustain life and perform other vital soil functions.
• Soil pores exist between and within aggregates and are occupied by water and air.
• Macropores are large soil pores, usually between aggregates, that are generally greater than 0.08
mm in diameter. Macropores drain freely by gravity and allow easy movement of water and air.
They provide habitat for soil organisms and plant roots can grow into them.
• With diameters less than 0.08 mm, micropores are small soil pores usually found within
structural aggregates. Suction is required to remove water from micropores.

40. • sustaining biological productivity, regulating and partitioning water and
solute flow, and cycling and storing nutrients.
• Granular structure is typically associated with surface soils, particularly
those with high organic matter. Granular structure is characterized by
loosely packed, crumbly soil aggregates and an interconnected network of
macropores that allow rapid infiltration and promote biological
productivity.
• Structure and pore space of subsurface layers affects drainage, aeration,
and root penetration.
• Platy structure is often indicative of compaction.