Principles and Methods of Fertilizer Application

• Principles of Fertilizer Application

Fertilizer use should be based on 4R Nutrient Stewardship:

• Right Source – matching fertilizer type with crop needs (e.g., urea for N, DAP for N+P).
• Right Rate – based on crop requirement, soil fertility, and yield target.
• Right Time – synchronizing with crop demand to reduce losses.
• Right Method – choosing placement to minimize loss and maximize availability.

Key Principles

• Nutrient Balance: Apply nutrients in balanced proportion (N:P:K + secondary/micronutrients). Overuse of N reduces yield quality and induces P, K, Zn deficiency.
• Soil Fertility Consideration: Test-based application (STCR – Soil Test Crop Response). High fertility soils → lower dose; low fertility → higher dose.
• Crop Requirement: Different crops need different nutrients (e.g., sugarcane requires more K, legumes require less N but more P).
• Nutrient Use Efficiency (NUE): Split application, proper placement, use of inhibitors, and fertigation improve efficiency.
• Avoiding Losses: Minimize leaching, volatilization, denitrification, fixation by using proper timing and placement.
• Environmental Safety: Prevent groundwater nitrate pollution and greenhouse gas emissions.

Methods of Fertilizer Application

• Broadcasting: Fertilizers spread uniformly over the soil surface, before or after sowing.

Types:

1. Basal broadcasting – before sowing, followed by ploughing.
2. Top dressing – applied to standing crop (e.g., urea for wheat, rice).

Advantages: Simple, quick, low labor cost.

Disadvantages:

• Low efficiency (30–50% for N).
• High nutrient losses (volatilization, leaching).
• Not suitable for P and K in heavy soils.

• Placement: Fertilizer placed close to root zone at depth.

Types:

• Plough sole placement – fertilizer placed at plough layer bottom.
• Deep placement – e.g., urea super granules (USG) in rice.
• Localized placement – near seed or plant.

1. • Band placement: Fertilizer applied in bands (side-band, below-band).
   • Hill placement: Fertilizer applied in ring/hill around plants (e.g., sugarcane, maize).

Advantages:

• Higher nutrient use efficiency (N 50–60%, P up to 90%).
• Minimizes fixation (esp. for P and K).
• Saves fertilizer cost.

Disadvantages:

• Requires more labor/machinery.
• Not suitable for dense crops like wheat.

• Foliar Application; Fertilizer nutrients sprayed on leaves in solution form.

Examples:

• 2% urea spray for rice/wheat.
• 0.5% ZnSO₄ spray for rice and maize.
• Micronutrients (Fe, Mn, B, Mo) commonly applied as foliar spray.

Advantages:

• Quick correction of deficiencies.
• Useful under adverse soil conditions (fixation, alkalinity, drought).

Disadvantages:

• Limited nutrient supply.
• Possible leaf scorching if high concentration used.

• Fertigation; Application of fertilizers through irrigation water (drip/sprinkler).

Advantages:

• Precise and uniform distribution.
• Saves 30–40% fertilizer and water.
• Increases yield by 20–30%.
• Suitable for high-value crops (vegetables, fruits, sugarcane).

Disadvantages:

• Requires water-soluble fertilizers.
• Initial cost of drip system is high.

Starter Solution / Seed Treatment

• Seed soaking or coating with fertilizers.
• Example: Mo seed treatment for legumes, P-solubilizer coating.

Fertilizer Application in Standing Water (Paddy)

• Deep placement of Urea Super Granules (USG) or Briquettes → reduces N loss by denitrification.

Other Methods

• Pelleting: Seeds pelleted with P fertilizers for legumes.
• Root dipping: Seedling roots dipped in fertilizer slurry before transplanting (rice).
• Top dressing by drone / precision application: Emerging in smart agriculture.

Crop-Specific Examples

• Rice: USG deep placement, split N application, ZnSO₄ basal, P & K basal placement.
• Wheat: Split N application (½ basal + ½ top-dressing at tillering).
• Sugarcane: Band placement along furrows; heavy K requirement.
• Potato: Fertigation or band placement of NPK.
• Legumes: P basal placement, Mo/Zn seed treatment.

Principles of Fertilizer Application

• Right Source – Select appropriate fertilizer form depending on soil type & crop (e.g., SSP in acid soils, DAP in neutral soils, MOP in K-deficient soils).
• Right Rate – Apply recommended dose (based on soil test, crop requirement, yield goal).
• Right Time – Synchronize nutrient availability with crop demand (e.g., split N application in cereals).
• Right Method – Ensure efficient placement to minimize losses (broadcast, band, fertigation, foliar).
  👉 Known as 4R Nutrient Stewardship (Right source, Right rate, Right time, Right place).

Methods of Fertilizer Application

Solid Fertilizers

• Broadcasting
  • Over the entire field before sowing or standing crop.
  • Types: a) Basal broadcasting, b) Top dressing.
  • Advantages: Easy, suitable for dense crops like rice, wheat.
  • Disadvantages: Higher losses (volatilization, leaching), nutrient use efficiency low (~30–50%).
• Placement
  • Fertilizer placed close to root zone (5–7 cm away).
  • Types: a) Plough sole placement, b) Deep placement (urea supergranules in rice), c) Band placement.
  • Advantages: Reduces fixation, improves efficiency (N 50–60%).
  • Example: DAP with seed in bands; Urea supergranules in puddled rice.
• Drilling: Fertilizers applied along with seeds in furrows at sowing. Common in cereals, pulses, oilseeds.
• Side dressing: Fertilizer applied by the side of growing plants. Used for row crops like maize, sugarcane, cotton.
• Top dressing: Nitrogenous fertilizers applied on standing crop in split doses (e.g., wheat, rice).

Liquid Fertilizers

• Fertigation
  • Application of fertilizers through irrigation water.
  • High efficiency, uniform distribution, precise control.
  • Common in drip irrigation for high-value crops (vegetables, fruit crops).
• Foliar Application
  • Spraying nutrients directly on leaves.
  • Advantage: Quick remedy for micronutrient deficiencies (Zn, Fe, Mn, B).
  • Limitation: Only small quantities can be applied.

Specialized Methods

• Root dipping – Rice seedlings dipped in urea solution before transplanting.
• Seed treatment / seed pelleting – Coating seeds with nutrients (e.g., Mo for pulses, P for legumes).
• Localized deep placement – Urea supergranules or briquettes in rice to reduce N losses.
• Aerial application – Micronutrients sprayed in large areas (used in plantation crops).

🔑 Key Facts for ASRB NET

• Broadcasting efficiency: N use efficiency 30–50%.
• Placement efficiency: N efficiency ~50–60%; P efficiency improved as fixation is reduced.
• Deep placement of USG in rice → increases N efficiency by 20–25%.
• Foliar spray concentration: Urea 2%, ZnSO₄ 0.5%, FeSO₄ 0.5%, Borax 0.2%.
• Fertigation: Increases fertilizer use efficiency by 80–90%.
• Seed pelleting: Mo deficiency correction in pulses.
• Best method for P: Placement, since broadcasting increases fixation.
• Efficiency of fertilizer use:
  • Broadcasting N: ~30–50% recovery.
  • Placement N: 50–60%.
  • Foliar application: ~80–90% recovery (for micronutrients).
• USG in rice: Saves 30–40% N.
• Fertigation: Saves 25–40% water + fertilizer, yield ↑ 20–30%.
• Micronutrient efficiency: Best by foliar spray.
• Mo (Molybdenum): Always applied as seed treatment for legumes.
• P fertilizers: Best applied by placement (banding) to avoid fixation.