Fundamentals of Soil
• basic principles of tropical soils
• Soil composition
• Soil Organic Matter
• Soil Water
• Soil Air
• Soil is the mixture of minerals, organic matter, gases, liquids and a
myriad of organisms that can support plant life. It is a natural
body that exists as part of the exosphere and it performs four
important functions: it is a medium for plant growth; it is a means
of water storage, supply and purification; it is a modifier of the
atmosphere; and it is a habitat for organisms that take part in
decomposition and creation of a habitat for other organisms.
Critical Nutrient Levels
• There are 12 essential elements which plants obtain from the soil that are commonly
managed by growers. In addition, plants require carbon, hydrogen, and oxygen to
• What makes an element essential to plant growth?
• An element is essential if the plant cannot complete its life cycle without the element.
• It is essential if the element is directly or indirectly involved in the metabolic processes of
the plant (i.e. photosynthesis or respiration).
• A deficiency in an essential nutrient will result in the development of a
characteristic, visual symptom.
The essential elements for plant growth
Element Abbreviation Source
Carbon C Air
Hydrogen H Air/Water
Oxygen O Air/water
Nitrogen N Air/Soil
Phosphorus P Soil/Water
Potassium K Soil/Water
Element Abbreviation Source
Sulfur S Soil/Water
Calcium Ca Soil/Water
Magnesium Mg Soil/Water
Iron Fe Soil/Water
Zinc Zn Soil/Water
Manganese Mn Soil/Water
Molybdenum Mo Soil/Water
Boron B Soil/Water
Copper Cu Soil/Water
What Your Plants Need
N = Nitrogen, P = Phosphorous, K = Potassium (potash)
• Nitrogen is essential for vigorous leaf growth and tends to increase fruit set. Sources of Nitrogen are:
Bloodmeal, Bone Meal, Cottonseed Meal, Manure, and Activated Sludge.
Phosphorous is essential for strong root systems and bright flowers. It can increase fruit development and
seed yield. Sources of Phosphorous are Activated Sludge, Bloodmeal, Bone Meal, Cottonseed Meal, and
Potassium is essential for cell division and strong stems. It helps fight diseases, improves quality of fruit,
and decreases water requirement of plants. Sources of Potassium are: Greensand, Manure, Compost, and
Trace Elements need for strong, healthy plants are: Boron, Calcium, Cobalt, Copper, Iodine, Iron,
Magnesium, Molybenum, Sulfur, Tin, Zinc. Sources are: Oyster Shell Flour, Leaf Mold, Seaweed, Phosphate
Rock, and Compost.
• Soil bacteria are very important in biogeochemical cycles and have been used
for crop production for decades. Plant–bacterial interactions in the
rhizosphere are the determinants of plant health and soil fertility. Free-living
soil bacteria beneficial to plant growth, usually referred to as plant growth
promoting rhizobacteria (PGPR), are capable of promoting plant growth
by colonizing the plant root. PGPR are also termed plant health promoting
rhizobacteria (PHPR) or nodule promoting rhizobacteria (NPR). These are
associated with the rhizosphere, which is an important soil ecological
environment for plantmicrobe interactions.
Soil Bacteria - cont
• Free-living nitrogen-fixing bacteria or associative nitrogen fixers, for example
bacteria belonging to the species Azospirillum, Enterobacter, Klebsiella
and Pseudomonas, have been shown to attach to the root and efficiently
colonize root surfaces. PGPR have the potential to contribute to sustainable
plant growth promotion. Generally, PGPR function in three different ways:
synthesizing particular compounds for the plants, facilitating the uptake of
certain nutrients from the soil, and lessening or preventing the plants from
Soil Bacteria - cont
• PGPR also help in solubilization of mineral phosphates and other
nutrients, enhance resistance to stress, stabilize soil aggregates, and improve
soil structure and organic matter content. PGPR retain more soil organic N,
and other nutrients in the plant– soil system, thus reducing the need for
fertilizer N and P and enhancing release of the nutrients
How microorganism do
Capable of nitrogen fixation from the air. And converted to
nitrates so that plants use.
Why do plants need nitrates?
• Plants need nitrogen for the synthesis of the protein's peptide bonds as well as for the nitrogen found in seven
of the twenty possible amino acid R- group side-chains which are needed for making proteins, and proteins
are needed for Cell growth.
When a plant does not get enough nitrogen it will suffer from stunted growth.
Plants obtain nitrogen through their roots in either the form of nitrate or ammonium.
Atmospheric nitrogen - N2 - cannot be utilized by the Plant.
Amino acids are used to create vital structural proteins and functional enzymes which allow
the plant to grow and develop.
Why do plants need nitrates? - cont
• nitrogen is important macro nutrient for all organism. Nitrogen is essential for
growth and reproduction of all plants. It is a basic constituent of proteins.
Under normal growing conditions plants use nitrogen to form plant proteins. When
normal growth is altered, protein formation may be slowed.
the plant can not absorbs the free nitrogen present in air. It absorbs the nitrogen
present only in nitrate forms present in soil.
so for normal growth of plant nitrates are very essential
• Plants need nitrates to grow, develop and produce seed. Nitrates are turned into
amino acids, which are, in turn, formed into protein molecules. Its deficiency is
characterised by poor growth and yellow leaves.
How microorganism do
In general, natural phosphates, usually in the form insoluble.
Or is held with other substances. Microorganisms will digest
and release phosphate into a form that Plant which can be
And phosphate buffer, also have as well. Make the soil pH
constant not acidic or too alkaline.
Phosphorus Forms and Functions
• Forms of Phosphorus available for Plant Uptake
• The orthophosphates, H2PO4
- and HPO4
2-, are the primary forms of phosphorus taken
up by plants.
• When the soil pH is less than 7.0, H2PO4
- is the predominate form in the soil.
• Although less common, certain organic phosphorus forms can also be directly taken up
Functions of Phosphorus in Plants
• Phosphorus is involved in many plant processes, including:
• Energy transfer reactions
• Development of reproductive structures
• Crop maturity
• Root growth
• Protein synthesis
Why do plants need phosphates?
• Phosphorus is an element which is absorbed by plants through the soil. It is a part of the
photosynthesis cycle, which allows plants to convert carbon dioxide into oxygen.
• Plants need phosphate to stimulate root development and flowering and to help in the
prevention of disease and stress. Phosphate is used in making soft drinks, detergents &
• Phosphorus encourages plant growth, including flowers, fruits and seeds.
• A plant needs phosphorus and calcium to keep its inner skeletal structures strong; plants
lacking in these minerals will look weak and spindly.
• In general, roots absorb phosphorus in the form of orthophosphate, but can
also absorb certain forms of organic phosphorus. Phosphorus moves to the
root surface through diffusion. However, the presence of mycorrhizal fungi,
which develop a symbiotic relationship with plant roots and extend
threadlike hyphae into the soil, can enhance the uptake of phosphorus, as
well especially in acidic soils that are low in phosphorus.
How microorganism do
Most potassium in the soil will be pinned to the soil particles. Plants cannot used
microorganisms are separated by potassium out of soil particles and plant can used
Why do plants need potassium?
• potassium enters in the formation of chlorophyll. it mostly affects the
growth of plants since it activates certain enzymes essential for
photosynthesis and respiration.
• potassium helps prevent plants from drought and help them use water it also
makes the fruits and vegetable
• K+ ions are needed for protein synthesis. Also, they control the opening and
closing of the stomata
How microorganism do
• Plant disease control
Many types of microorganisms can destroy pathogens on plants, such
as some species of Bacillus subtilis & Trichoderma harzianum can
destroy the bacteria Colletotrichum musarum bordered cause of
Anthracnose disease in fruit
microorganisms some species can destroy pests remarkably Bacillus
thuringiensis can destroy caterpillars , A fungus Paecilomyces lilacinus
useful in controlling Eggs of insects effectively.
Why we reduce chemicals used
• 73% of farmers in Thailand are toxins in the body overthan standard of World
• Every year, farmers in Thailand cases and deaths is a lot due to the use chemicals
• Agricultural produce from the use of chemicals not safe for consumption.
• High production cost
• Ecology and soil structure damage. Disease and insect are resistant symptoms Thus
the need for more concentrated chemical control. Which are harmful to farmers
Why we need to use bio-organics agriculture
• Lower production costs
• Agricultural products safe for consumption.
• Safety and good for health of farmers
• Produce are good taste than using chemical fertilizers and chemical
• Not destroy Ecology
Management of soil acidity
• Land managers can manage soil acidity by raising the pH to a desired value through several
• Flooding: In lowlands systems, flooding may be an effective technique in raising the pH of the
soil. However, this effect is only good for the time for which the soil is flooded. Flooded or
paddy mineral soils are ‘self-liming’. When they are flooded and become anaerobic (lack of
oxygen in the soil atmosphere) for a period of time, the pH rises toward neutrality even when the
soil pH was originally acidic. If the soil is subsequently drained and becomes more aerobic (more
oxygen in the soil atmosphere), the pH will return to an acidic state
• However, care must be taken if the soil contains manganese-oxide minerals, since flooding conditions may
lead to manganese toxicity.
• Crop consideration is also required. Flooding conditions reduces the oxygen within the soil, which is needed
for plant life. As a result, crops that do not tolerate high amounts of water and low oxygen levels are not be
suited for flooded conditions. Taro and rice are examples of crops that grow well in flooded lowlands.
• Additions of organic matter: Additions of organic matter is a viable
option to manage problems associated with soil acidity. Organic matter
increases the cation exchange capacity of the soil. As the base saturation
increases, the relative amount of “acid cations” decreases.
• In addition, organic matter forms strong bonds, known as “chelates,” with
aluminum. Chelation reduces the solubility of aluminum and soil acidity.
Again, if your soil is prone to manganese toxicity, it is not suggested that you
add organic matter.
•Conventional Liming: Various liming materials may be added to the soil that neutralize, or
counteract, soil acidity. Liming materials are bases that react with hydrogen ions in the soil
solution to form water?
•Examples of common liming materials are limestone (calcium carbonate), dolomite (calcium/magnesium
carbonate), hydrated lime (calcium hydroxide), and quicklime (calcium oxide). Calcium and magnesium silicates
are also used as liming agents.
•Additions of wood ash: Like organic mater, wood ash increases base saturation and forms chelates with