Grade9||Materials Used in Agriculture||Notes

Materials Used in Agriculture

Introduction to Agricultural Materials

Agriculture relies on various materials to ensure healthy plant growth and high crop yields. Plants obtain essential nutrients from soil, but continuous cultivation depletes these nutrients, reducing soil fertility. To address this, farmers use fertilizers to replenish soil nutrients and insecticides to protect crops from pests. While these chemicals boost productivity, their excessive use causes environmental pollution, soil degradation, and health hazards.

Essential Plant Nutrients

Plants require 17 essential elements for proper growth and development. These elements are classified based on the quantity needed:

A. Primary/Macro Nutrients (Required in Large Amounts)

1. Nitrogen (N): Crucial for leaf growth, chlorophyll formation, and protein synthesis.
2. Phosphorus (P): Vital for root development, flower/fruit formation, and energy transfer.
3. Potassium (K): Important for stem strength, disease resistance, and enzyme activation.

B. Secondary/Micro Nutrients (Required in Smaller Amounts)

• Calcium (Ca): Cell wall structure and membrane permeability.
• Magnesium (Mg): Central component of chlorophyll.
• Sulfur (S): Protein synthesis and enzyme activation.
• Others: Iron (Fe), Zinc (Zn), Copper (Cu), Manganese (Mn), Boron (B), Molybdenum (Mo), Chlorine (Cl), Nickel (Ni).

Deficiency Symptoms:

• Nitrogen: Yellowing of older leaves (chlorosis), stunted growth.
• Phosphorus: Purple discoloration of leaves, poor root growth.
• Potassium: Brown scorching/curling of leaf tips, weak stems.

Fertilizers: Types, Uses, and Impacts

Definition:

Substances added to soil to supply essential nutrients for plant growth.

Classification:

1. Organic Fertilizers

• Sources: Animal manure, compost, green manure, bone meal, oil cakes.
• Preparation: Decomposition of organic matter by microorganisms.
• Examples:

1. Compost: Decomposed plant/animal residues.
2. Green Manure: Fast-growing plants plowed into soil (e.g., Sesbania, Sunn Hemp).
3. Farmyard Manure: Mixture of dung, urine, and litter.

Advantages:

• Improves soil structure and water retention.
• Releases nutrients slowly over time.
• Increases microbial activity in soil.
• Environmentally sustainable.

Disadvantages:

• Low nutrient concentration.
• Bulky and difficult to transport.
• Slow-acting compared to chemical fertilizers.

2. Inorganic/Chemical Fertilizers

Manufacture: Industrial chemical processes.

Types based on Nutrient Content:

TypeChemical FormulaNutrient ContentKey FunctionsNitrogenousUrea: CO(NH₂)₂46% NPromotes vegetative growth Ammonium sulfate: (NH₄)₂SO₄21% N PhosphaticSingle Superphosphate: Ca(H₂PO₄)₂ + CaSO₄16-20% P₂O₅Root development, flowering Triple Superphosphate: Ca(H₂PO₄)₂44-48% P₂O₅ PotassicMuriate of Potash: KCl60-62% K₂ODisease resistance, fruit quality Sulfate of Potash: K₂SO₄48-52% K₂O 

Advantages:

• High nutrient concentration.
• Fast-acting and soluble.
• Easy to store, transport, and apply.
• Precise nutrient application possible

Disadvantages:

• Causes soil acidity/alkalinity imbalance.
• Leads to soil hardening and reduced microbial activity.
• Groundwater pollution through leaching.
• Residual chemicals in food products.
• Requires repeated application.

NPK Fertilizers:

• Definition: Fertilizers containing all three primary nutrients (Nitrogen, Phosphorus, Potassium).
• Ratio: Expressed as N:P:K (e.g., 20:10:10).
• Importance: Balanced nutrient supply for overall plant development.

Insecticides: Types and Environmental Impact

Definition:

Chemicals used to control or eliminate insect pests that damage crops.

Classification:

1. Bio-Insecticides

• Nature: Derived from natural sources.
• Examples:

1. Plant-based: Neem extract, tobacco decoction, garlic-chili spray.
2. Microbial: Bacillus thuringiensis (Bt).
3. Traditional: Wood ash, cow urine mixture.

• Preparation Methods:

Jholmol: Fermented mixture of cow dung, urine, and plant parts.

Neem Solution: Soaked neem leaves in water.

Advantages:

1. Biodegradable and non-toxic.
2. Target-specific (less harm to beneficial insects).
3. No pest resistance development.
4. Safe for human consumption.
5. Limitations: Less potent, require frequent application.

2. Chemical Insecticides

Types:

1. Organochlorines: DDT, BHC, Aldrin (persistent in environment).
2. Organophosphates: Malathion, Parathion (affect nervous system).
3. Carbamates: Carbaryl, Aldicarb.
4. Pyrethroids: Cypermethrin, Deltamethrin.

Advantages:

1. Highly effective and fast-acting.
2. Broad-spectrum pest control.
3. Economical for large-scale farming.

Disadvantages:

1. Environmental Pollution: Accumulates in soil and water bodies.
2. Bio-magnification: Increases concentration up food chain.
3. Health Hazards: Carcinogenic, neurotoxic, respiratory problems.
4. Kills Beneficial Organisms: Bees, earthworms, natural predators.
5. Pest Resistance: Insects develop immunity over time.

Precautions for Using Chemical Insecticides:

1. Wear protective clothing (gloves, mask, goggles).
2. Follow recommended dosage and application timing.
3. Avoid spraying during windy conditions.
4. Store away from food and water sources.
5. Properly dispose of empty containers.
6. Maintain pre-harvest intervals (PHI).

Soil Conservation and Sustainable Practices

Importance of Soil Testing:

• Determines pH, nutrient levels, and deficiencies.
• Guides appropriate fertilizer selection and dosage.
• Prevents over-application and waste.

Sustainable Agricultural Practices:

• Crop Rotation: Alternating different crops to maintain soil fertility.
• Mixed Farming: Integrating crops and livestock.
• Green Manuring: Growing and plowing legumes to add nitrogen.
• Terracing: Preventing soil erosion on slopes.
• Mulching: Covering soil with organic material to retain moisture.
• Integrated Pest Management (IPM): Combining biological, cultural, and chemical methods.

Alternatives to Chemical Inputs:

• Vermicompost: Earthworm-processed organic waste.
• Bio-fertilizers: Nitrogen-fixing bacteria (Rhizobium), phosphate-solubilizing microbes.
• Companion Planting: Growing pest-repelling plants alongside crops.
• Trap Crops: Plants that attract pests away from main crops.