Types of Fertilizers

Form 2 Agriculture Lessons for JCE: Grow Your Knowledge

Success Criteria

Classify fertilizers.
Discuss the advantages and disadvantages of organic and inorganic fertilizers.

Fertilizers are broadly categorized into two main groups: Organic Fertilizers and Inorganic Fertilizers.

Classification of Fertilizers

1. Organic Fertilizers:

* Farmyard manure

* Compost manure

* Green manure

2. Inorganic Fertilizers:

* CAN (Calcium Ammonium Nitrate)

* DAP (Diammonium Phosphate)

* Compound fertilizers (e.g., Compound A, B, C, D)

* Sulphate of Ammonia

Organic Fertilizers: Exclusive Details

1. Farmyard Manure (FYM):

* Source: A mixture of animal dung, urine, and decomposed plant materials. Urine significantly increases its nitrogen content.

* Storage: Should not be stored in open places to prevent nutrient loss through:

* Volatilization: Nitrogen escaping as gas.

* Leaching: Nutrients washing away with rain.

* Recommendation: Store in a shade.

* Factors Influencing Quality:

* Type of Animal: Chickens and pigs produce higher quality manure due to richer nutrient content in their dung.

* Age of Animal: Generally, older animals produce higher quality manure as their digestion/absorption of food nutrients is less efficient. However, young animals on higher quality feeds can also produce high-quality manure.

* Plant Material (Bedding): Materials that decompose quickly (e.g., grasses, herbs) produce higher quality manure than slow-decomposing materials (e.g., sawdust, maize stalks, wood shavings).

* Period of Decomposition: Kraal manure (animal excreta + bedding) should be fully decomposed before application.

* Advantages of FYM:

* Cost-effective.

* Simple to prepare (no technical knowledge required).

* Improves soil structure.

* Aids in environmental cleanliness by removing waste.

* Utilizes locally available resources.

* Disadvantages of FYM:

* Bulky, making transport difficult.

* Releases nutrients slowly.

* Prone to nutrient loss from poor storage (leaching, erosion, volatilization).

* Can cause fungal infections if applied before complete decomposition.

* May introduce weeds to the field.

2. Green Manure:

* Preparation: Prepared from green plants ploughed into the soil before they flower.

3. Compost Manure:

* Preparation: Made from garbage and other household wastes, heaped and turned to facilitate decomposition.

* Advantages of Compost Manure:

* Does not require livestock for preparation.

* Large quantities can be prepared quickly.

* Utilizes a variety of locally available materials.

* Improves soil structure and aeration.

* Disadvantages of Compost Manure:

* Releases nutrients very slowly.

* Large quantities are required for application.

* Preparation is labor-intensive.

* Can introduce soil-borne diseases and pests.

Inorganic Fertilizers: Exclusive Details

Classification of Inorganic Fertilizers:

Inorganic fertilizers are classified based on:

Nutrient Composition
Reaction with the Soil

1. Types According to Nutrient Composition:

* **Straight Fertilizers:** Contain only one essential plant nutrient (Nitrogen, Phosphorus, or Potassium).
    * **Examples:**
        * Sulphate of Ammonia (21:0:0)
        * Ammonium Nitrate (35:0:0)
        * Calcium Ammonium Nitrate (26:0:0)
        * Urea (46:0:0)
        * Single Superphosphate (0:10:0)
        * Potassium Sulphate (0:0:40)

* **Compound Fertilizers:** Contain two or three essential fertilizer elements (NPK - Nitrogen, Phosphorus, Potassium). Those containing all three are called complete compound fertilizers (e.g., Compound A, B, C, D). Incomplete compound fertilizers contain two (e.g., 20:20:0, 23:21:0+4s, Diammonium Phosphate (21:52:0)).

2. Types According to Reaction with the Soil:

* **Acidic Fertilizers:** Increase soil acidity or lower soil pH (e.g., Sulphate of Ammonia).
* **Basic Fertilizers:** Reduce soil acidity or raise soil pH.
* **Neutral Fertilizers:** Have no influence on soil pH.

Identification and Properties of Inorganic Fertilizers:

STRAIGHT FERTILIZERS:
- Nitrogenous Fertilizers:
  - Properties:
    - Readily soluble in water.
    - Short residual effects on the soil.
    - Can scorch or burn plants on contact.
    - Highly volatile (change to gas) when applied to dry soil.
    - Highly leached, especially with high rainfall.
    - Hygroscopic (absorb moisture from the atmosphere).
    - Can corrode skin; avoid handling with bare hands.
  - Effects of Excess Application:
    - Increased incidence of certain leaf diseases (e.g., rice blast).
    - Poor malting in barley.
    - Poor combustibility in tobacco.
    - Lodging of cereal crops.
    - Excessive vegetative growth at the expense of tuber formation in root crops (e.g., Irish potatoes).
  - Examples:
    - Sulphate of Ammonia (SA), (NH4)2 SO4: 21% N, 26% S. White, crystalline. Highly volatile, acid-inducing.
    - Ammonium Nitrate (AN), NH4NO3: 34-35% N (equal ammonium and nitrate forms). White crystalline, highly explosive in refined state.
    - Ammonium Sulphate Nitrate (A.S.N), (NH4)SO4 NH4NO3: Mixture of SA and AN. Yellow or orange, granular. 26% N (6.5% nitrate, 19.5% ammonium), 13.5% S. Acidic, hygroscopic, scorching effect.
    - Calcium Ammonium Nitrate (CAN), NH4NO3+CaCO3 (Nitro chalk): 21% N (10% ammonium, 11% nitrate). 10-20% quick lime (calcium oxide). Granular, greyish, hygroscopic. Neutral due to calcium.
    - Urea, CO(NH2)2: Most concentrated N fertilizer (45-48% N, all ammonium). Granular, white, slightly acidic, extremely water soluble. Highly hygroscopic, volatilizes quickly. Applied as foliar feed (e.g., pineapple) and in livestock feed processing.
    - Note: Only a portion of applied nitrogen is absorbed by plants.
- Phosphate Fertilizers:
  - Properties:
    - Much of the naturally occurring phosphate in soil is unavailable to plants.
    - Form insoluble compounds with other soil minerals.
    - Not readily leached.
    - Slightly soluble in water.
    - In acidic soils, much is converted to insoluble (fixed) compounds.
    - Long residual effect (can last up to 4 years).
    - Slight scorching effect, unlike nitrogenous/potassic fertilizers.
  - Examples:
    - Single Super Phosphate (S.S.P), Ca(H2PO4)2 CaSO4: 18-21% P2O5. Contains sulfur (distinguishes from double/triple). Granular, creamy-white (whiter due to high lime content). Releases P2O5 as calcium phosphate slowly. Neutral.
    - Double and Triple Super Phosphate (D.S.P or T.S.P): Granular, grey. Contains ~40-49% P2O5.
    - Soda Phosphate: Up to 20% P2O5. Contains other elements (30% CaO, 30% FeO, small amounts of Mg, Cu, Zn, Co, Mo, B). Good for soils lacking trace elements. Grey, powdery.
    - Basic Slag: 15-16% P2O5, 40-50% lime. Suitable for heavily acidic soils (e.g., clay). Contains trace S, Mn, Mg, Fe, Co, Cu, Mo. Highly basic; should not be mixed with other fertilizers. Grey, powdery.
    - Note: DAP and Urea are considered “high analysis” fertilizers due to their high content of essential nutrients (phosphorus and nitrogen, respectively).

General Advantages and Disadvantages

Organic Fertilizers:

* Advantages:

* Supplies a wide range of plant nutrients.

* Improves soil structure.

* Helps maintain soil pH.

* Long-lasting influence in the soil.

* Disadvantages:

* Low nutrient values.

* Difficult to determine precise application quantities.

* Bulky, making transport and large-scale application difficult.

* Slow release of plant nutrients.

Inorganic Fertilizers:

* Advantages:

* Supplies required nutrients in precise quantities.

* Easy to transport.

* Easy to apply on large farms.

* Provides instant results upon application.

* Disadvantages:

* Expensive.

* Complex to manufacture.

* Can make soil acidic if acid-forming fertilizers are applied.