Unit 9b :Functions, sources & causes of depletion

Form 1 Agriculture Lessons for JCE: Grow Your Knowledge

Nitrogen (N)

Functions
- Gives dark green color to plant leaves as it is part of the chlorophyll molecule.
- Important in the formation of protein molecules.
- Encourages vegetative growth in plants, increasing height/length and leaf sizes.
- Makes plants and their fruits succulent (important for herbs, cabbages, lettuce, carrots, melons, cucumbers).
- Increases yield of cereals and legumes by increasing grain size.
- Controls the use of phosphorus and potassium in plants.
Sources
- Inorganic fertilizers such as Calcium Ammonium Nitrate (CAN-21%N) and Urea (46%N).
- Organic manures such as compost and farmyard manure (FYM).
- Fixation by symbiotic Rhizobium bacteria and free-living bacteria (Azotobacter) through the nitrification process.
- Nitrification of atmospheric nitrogen through lightning.
Depletion
- Volatilization: Nitrogen is released into the atmosphere as a gas through activities of denitrifying bacteria.
- Immobilization: Used by microorganisms to build up their bodies.
- Absorption by plants and the consequent removal of crop plants (products) from the land through harvesting.
- Soil erosion: Carries away nitrates, together with the topsoil, down the slope.
- Leaching: Nutrients (nitrates) are washed vertically down the soil profile.

Functions
- Encourages formation of strong roots and stems.
- Encourages seed germination, flowering, fruit formation, and maturity of crops.
- Speeds up ripening of fruits.
- Improves the quality of pastures and vegetables.
- Increases the resistance of crops to diseases.
- Encourages plant growth because it helps in the production of new cells.
- Important in the process of respiration and manufacturing of fats and carbohydrates.
- Used in enzyme and protein formation.
Sources
- Artificial fertilizers such as single superphosphate, double superphosphate, and triple superphosphate.
- Organic manure such as farmyard manure, compost, and green manure.
- Weathering of phosphate-containing rocks which release phosphate salts like calcium phosphates.
Depletion
- Plant absorption and crop removal.
- Fixation through adsorption into silicate clays.
- Leaching.
- Soil erosion.

Functions
- Makes the stem strong, reducing lodging and increasing the plant’s resistance to bacterial disease.
- Important in the formation of carbohydrates.
- Makes the transportation of fluids in plants possible, leading to well-filled seeds and tubers.
- Helps in absorption of nitrates from the soil.
- Controls the opening and closing of the stomata.
- Improves the quality of fruits and vegetables.
Sources
- Inorganic fertilizers such as Muriate of Potash (KCl), Potassium Sulphate, and Potassium Nitrate.
- Organic manures and crop residues.
- Potash rocks like mica and feldspar.
Depletion
- Absorption by plants.
- Soil erosion.
- Leaching.
- Adsorption (fixation in soil particle of some clay).

Functions
- Helps the cell walls to be strong.
- Helps in transportation and storage of carbohydrates and proteins into seeds and tubers.
- Neutralizes soil pH, which makes phosphorus and potassium available.
- Increases the activities of nitrogen-fixing bacteria.
Sources
- Commercial fertilizers such as CAN.
- Crop residues and manure.
- Weathering of soil minerals such as limestone.
- Agricultural lime such as dolomite, calcium carbonate, and quicklime (CaO).
Depletion
- Absorption by plants.
- Erosion.
- Leaching.

Functions
- Is a component of chlorophyll, responsible for photosynthesis.
- Increases the amount of oil stored in groundnuts and soybeans.
- Activates enzymes in the metabolism of carbohydrates and nitrogen.
Sources
- Inorganic fertilizers.
- Organic manures.
- Dolomitic lime.
- Weathering of magnesium-containing rocks.
Depletion
- (Not explicitly detailed in the provided text for depletion specifically, but implied by plant absorption and environmental loss similar to other nutrients).

Functions
- Increases the amount of stored oil in sunflower, groundnuts, and soybeans.
- Is a constituent of three amino acids: cystine, cysteine, and thiamine.
- Useful in nodule formation on legume roots for nitrogen fixation.
- Needed in protein synthesis and improves the biological value of proteins.
Sources
- Inorganic fertilizers such as ammonium sulphate and 23:21:0+4S.
- Oxidation of sulphides such as copper sulphide (CuSO2), Iron sulphide (FeSO2) forms sulphates.
- Rainwater.
- Atmospheric Sulfur from industries where coal is burnt to release Sulphur dioxide (SO2).
Depletion
- Plant absorption and crop removal.
- Volatilization in the form of hydrogen sulphide gas (H2S).

Functions
- Necessary for the formation of chlorophyll.
- Activates various respiratory enzymes.
Sources
- Inorganic enriched fertilizers and chelates.
- Organic manure.
Depletion
- Soil erosion.
- Leaching.
- Fixation into insoluble forms.

Functions
- Activates enzymes and acts as a catalyst in the formation of chlorophyll.
Sources
- Fertilizers like manganese sulphate are used to correct deficiency.
- Organic matter.
Depletion
- Soil erosion.
- Leaching in acidic soil conditions.
- Fixation in alkaline soils.

Functions
- Essential for cell division in meristematic tissue.
- Regulates carbohydrate mechanism.
- Important in the transfer of sugars (starch) within the plant.
Sources
- Fertilizers and borax.
Depletion
- Soil erosion.
- Leaching.

Functions
- Promotes symbiotic nitrogen fixation in legumes.
- Increases nitrogen utilization.
Sources
- Inorganic enriched NPK fertilizers.
- Organic matter.
Depletion
- Soil erosion.
- Leaching in alkaline soils.
- Fixation into insoluble forms by ferrous oxides in acidic forms.