This document discusses humus, which refers to the stable fraction of soil organic matter that results from the decomposition of plant and animal materials. It defines humus and distinguishes it from total organic matter. Humus is composed of humic substances like fulvic acids, humic acids, and humin. The document outlines the key properties and benefits of humus, including its impact on soil structure, aeration, water retention, buffering capacity and support of biological life. It emphasizes the importance of maintaining or increasing humus levels through practices like adding organic matter, using low-till practices, and growing cover crops.

2. SUBMITTED BY
PREETHI.K.D
2014602009

3. humus ( Latin humus: earth, ground) refers to
the fraction of soil organic matter.
• In the earth sciences, "humus" means any organic matter
which has reached a point of stability, where it will break
down no further.
• In agriculture, "humus" is often used simply to mean mature
compost, or natural compost extracted from a forest or
other spontaneous source for use to amend soil.

4. Organic matter and humus
• Although the terms "organic matter" and "humus"
are often used interchangeably, they are not
interchangeable.
• Humus is a small, stable portion of the total organic
matter in soil.
• The process by which dead material and modified
organic matter forms the more complex and stable
humus is known as humification.

5. Soil humus
• Mixture of organic compounds produced upon
decomposition of plant tissues
• Structureless component of the soil fraction,
• primarily derived from the decomposition of OM and
by microbial synthesis of biological products

6. Composition of humus
• Humus can be divided into different humic
substances: fulvic acids, which are soluble in
water of any acidity; humic acids, which are
darker in color and soluble in all but the most
acidic conditions; and humin, the insoluble
portion of humus.

7. Properties of humus
• Humus is highly colloidal and amorphous.
• Its surface exposure, adsorption catalysis are far in
excess that those exhibited by clays.
• CEC varies from 100-300 meq/100g. Presence of
1% of humus in a mineral soil means an extra CEC of
2 meq / 100g of soil.
• Humus is hydrophilic and improves the WHC of
soils. From a saturated atmosphere humus absorb
80-90% water while clay absorbs only 15-20%

8. Cont…
• Humus has less adhesion and cohesion properties.
In clay soil this property helps to allocate
unfavourable structural properties.
• Humus has a very favorable effect on aggregate
formation and stability.
• Impart black colour to soils.

9. Properties of humus

10. Influence on soil properties

11. Soil structure
• Humus has a profound effect on the structure of many
soils.
• A humus-rich topsoil allows easier tilling, reduced
erosion, less-frequent irrigation and better root growth.
• Promotes fragmentation into clayish soils (crumby
texture) that facilitate draining, soil tilling and root
development.
• Intensive tillage - deterioration of structure
• less severe in soils adequately supplied with humus.
• When humus is lost, soils tend to become hard, compact
and cloddy.

12. Aeration, water-holding capacity and permeability.
• favorably affected by humus.
• The frequent addition of easily decomposable
organic residues leads to the synthesis of
complex organic compounds that bind soil
particles into structural units called aggregates.
• These aggregates help to maintain a loose, open,
granular condition.
• Water is the better able to infiltrate and percolate
downward through the soil.

13. Cont..
• The roots of plants need a continual supply of
O2 in order to respire and grow.
• Large pores permit better exchange of gases
between soil and atmosphere.
• Humus usually increases the ability of the soil
to resist erosion
• it enables the soil to hold more water.

14. Other properties
Buffering capacity :
• Humus colloids protect microbes and plants from excessive,
damaging sodium, magnesium and potassium, minerals that
are positively charged and attracted to the negative charge of
the humus colloid.
• The colloid also buffers and enhances carbon, sulfur,
phosphorus and nitrogen.
• Additionally, humus can form complexes with metal ions and
compounds, including toxic pollutants. This property can
reduce toxicity or capture pollutants.

15. Humus is alive
• Humus is not just soil, it is a community of living
things.
• Organic matter is a breeding ground for many types
of microbes, including bacteria and fungi which
break down plant material, and for other
microorganisms that help plants roots absorb
necessary nutrients.
• Earthworms have long been known to loosen the soil
for plant roots. Recent research indicates that
earthworms may serve to eliminate unwanted
pathogens from the soil as well.

16. A true power generator of soil life, it enhances
active and diversified biological life.

17. Benefits
• There are many benefits of humus compost to the soil. As a
simple reminder, we like to use the acronym “DIP ‘N’
CHEW”
• D isease suppression — humus compost has a healing
effect on plants and a cleansing action on soils.
• I ncreases plant yield
• P orosity increased in the soil-has more air voids than
typical soils.
• N utrient retention — magnetic charge from high CEC holds
nutrients longer.
• C ompaction reduction — it makes soil spongy and enables
it to spring back.
• H elps reduce dependence on chemicals — promotes
healthier plants.
• E rosion reduced-disperses the force of raindrops.
• W ater retention increased — like a sponge holding water.

18. How to increase?
To maintain or increase the level of humus in
soil, it is important to ensure
• a steady, adequate, supply of crop residue and
organic matter.
• Use low or no-till practices,
• responsibly fertilize crops to increase plant
mass, and grow cover crops

19. Thank you