Basis & Important Resource of
ORGANIC AGRICULTURE
SOIL
an upper thin layer of the earth
composed of mixture of fragments of
rocks, organic matter, water & air
in varying proportions and having
developed horizontal layers
produced through the action of climate
and living organisms
SOIL PROFILE
Organic original forms
still recognizable
Admixture of organic
matter/humus, minerals
(top soil)
Contains substances leached
from A horizon, less fertile,
low in o.m., less growth of
microorganisms
Zone of minimum change;
the layer where A & B horizons
are derived (parent material)
Kind and type of soil developed
depends on the kind of parent
material
Red
soil
Yellow soil
White soil
Black soil
Fertile Soil
Minerals
though there are 100 elements found in nature,
only 8 principal chemical elements are present
in the mineral matter
Oxide
Magnesium
Silicate
Calcium
Aluminum
Sodium
Iron
Potassium
ORGANIC MATTER (OM)
“One Who Calls the Shots”
serves as reservoir of the different
elements needed by plant
improves the water-holding
capacity of the soil
has a buffering capacity in the
regulation of soil pH
natural home of the different
microorganisms, fungi, bacteria,
algae, actinomycetes, etc
contains “humus”(the final and
stable product of decomposition)
influence on soil physical properties
high cat-ion adsorption capacity
A depleted soil which lacks Organic Matter
Three (3) Basic Properties of Soil
Physical Property
soil texture
soil structure
soil color
soil temperature
Chemical Property
a) Soil pH
-
a numerical system to express
the acidity of the soils
- one of the most if not the most
important fertility factor of the
soil
Why is pH important?
the chemical reactions & microbial
activities in the soils are largely
controlled by soil reaction
availability of essential plant nutrients
& existence of toxic elements in soil
depend so much on pH
Classification of Soils as to level of pH
pH 7
neutral soils (neither
acidic nor alkaline)
lower than pH7
more acidic soils
above pH 7
more alkaline soils
the ideal soil pH for most crops is 6.0 – 7.0
most favorable to availability of
nutrients
enhances microbial activities in
the soil, nitrogen fixation, faster
decomposition,etc)
b) Cation Exchange Capacity (CEC)
total cations adsorbed in the soil
affected by the level of soil pH
amount of organic matter
type and amount of clay
c)
% Base Saturation
- Percentage of CEC saturated by bases
( Ca , Mg, K, Na, Al)
Application/Importance of Base Saturation
assessment of lime requirement in
acid soils
soil classification
BIOLOGICAL PROPERTY
Diverse population of Macro &
Microorganisms which facilitate various
Biological and Chemical processes in
the soil
IMPORTANCE OF SOIL MICROORGANISMS
maintain soil fertility
clean up all dead organic materials
fix gaseous Nitrogen into forms that
can be used by plants to mainly- fertility
of soil
can be used to extract minerals
are the prime food for all marine &
fresh water life
effectively degrade “xenobiotic” compounds
(herbicides & pesticides) example:
desulfomonile – a sulfate-reducing
bacterium which degrades chlorinated
pesticides (frequent chemical pollutants
in ground water)
1 cm of top soil is developed in 10’s
of thousands of years
It takes time to rehabilitate or
rebuild a depleted soil
Since “SOIL” is the
“Power House in Agriculture”
It is subjected to various forces/ elements in the
environment which affect its condition and life/
life cycles
Two (2) most Important Life Cycles
Currently Affects Climate & Agriculture
Nitrogen Cycle
Carbon Cycle
NITROGEN CYCLE
CARBON CYCLE
Issues that should be Addressed
Depletion of Soil Resource
Pollution and
Destruction of
Chemical Farming
Climate Change /Environmental Degradation
Erratic weather
condition
Flooding
Thank You Very Much!