Methods of Fertilizer Recommendation to Crops

Introduction

• Fertilizer recommendation is the scientific process of deciding the right fertilizer source, right dose, right time, and right method of application to achieve optimum crop yield, economic efficiency, and sustainable soil fertility.
• With the introduction of high-yielding varieties (HYVs), intensive cropping systems, and site variability in soil fertility, traditional blanket recommendations are no longer sufficient. Hence, scientific fertilizer recommendation approaches are essential for balanced nutrient management, as emphasized by ICAR and the 6th Deans’ Committee.

Objectives of Fertilizer Recommendation

• To supply nutrients according to crop requirement
• To avoid nutrient deficiency, excess, and imbalance
• To improve fertilizer use efficiency (FUE)
• To reduce cost of cultivation
• To maintain soil fertility and productivity
• To minimize environmental pollution
• To support sustainable agriculture

Methods of Fertilizer Recommendation to Crops

I) Blanket Fertilizer Recommendation

Meaning

• A fixed and uniform fertilizer dose recommended for a crop over a large area.
• Based on average soil fertility, past field experience, and results of regional trials.

Merits

• Simple and easy for farmers to follow.
• Useful where soil testing facilities are not available.
• Requires minimum technical knowledge.
• Suitable for traditional and rainfed farming systems.

Limitations

• Ignores variation in soil fertility from field to field.
• May result in over- or under-application of fertilizers.
• Low fertilizer use efficiency.
• Not suitable for precision or intensive agriculture.
• Example: State-level recommended NPK dose for wheat.

II) Soil Test–Based Fertilizer Recommendation

Meaning

• Fertilizer dose is determined based on laboratory analysis of soil samples.
• Soils are categorized as low, medium, or high in nutrient availability.

Principle: Fertilizer requirement decreases as native soil nutrient availability increases.

Merits

• Scientific and more accurate than blanket recommendations.
• Helps maintain soil nutrient balance.
• Improves fertilizer use efficiency.
• Reduces unnecessary and excess fertilizer use.
• Forms the basis of the Soil Health Card Scheme.

Limitations

• Requires soil testing laboratories and technical support.
• Time gap between sampling and recommendation may reduce accuracy.
• Results vary with soil test method and calibration.

III) Crop Response–Based Fertilizer Recommendation

Meaning

• Fertilizer recommendations are developed based on the yield response of crops to graded levels of fertilizers.
• Data are generated from long-term field experiments, where different fertilizer doses are applied and crop response is recorded.
• The optimum fertilizer dose is identified from the response curve that gives maximum economic yield.

Salient Features

• Establishes the relationship between fertilizer dose and crop yield.
• Helps in understanding nutrient requirement and response pattern of different crops.
• Forms the scientific base for regional and crop-specific recommendations.

Merits

• Directly linked with crop performance and yield response.
• Useful in identifying optimum and economic fertilizer doses.
• Helps develop recommendations for a specific region and cropping system.
• Provides experimental evidence for fertilizer planning.

Limitations

• Time-consuming and costly due to long-term experimentation.
• Recommendations are location-, soil-, and season-specific.
• Does not adequately consider current field-level soil fertility variations.
• Limited applicability for precision and site-specific farming.

IV) Targeted Yield Approach (STCR – Soil Test Crop Response)

Developed by: Indian Council of Agricultural Research (ICAR)

Concept

• A quantitative and scientific approach where fertilizer doses are calculated to achieve a pre-determined or targeted yield level.
• Integrates soil testing, crop response, and fertilizer efficiency into a single recommendation system.

Basic Considerations: This approach is based on three key parameters:

• Nutrient requirement per unit yield of the crop
• Contribution of nutrients from soil
• Contribution efficiency of fertilizers

General Formula: Fertilizer dose = Fertilizer efficiency (Nutrient requirement × Target yield − Soil contribution)​

Salient Features

• Provides site-specific and yield-oriented recommendations.
• Fertilizer dose increases or decreases according to soil fertility and yield target.
• Widely used for major cereals and field crops.

Merits

• Highly precise, scientific, and quantitative method.
• Ensures balanced fertilization according to crop demand.
• Improves fertilizer use efficiency and profitability.
• Avoids nutrient deficiency as well as excess application.
• Strongly recommended by ICAR for sustainable nutrient management.

Limitations

• Requires detailed soil testing and calibration data.
• Slightly complex and difficult for farmers without expert guidance.
• Needs periodic updating with new crop varieties and changing soil conditions.

V) Nutrient Balance (Removal) Approach

Principle: “The quantity of nutrients removed by crops through harvest must be replenished to maintain soil fertility.”

Basis of Recommendation

• Nutrient uptake pattern of the crop
• Expected yield level
• Nutrient removal through: Grain, Straw / biomass
• Continuous cropping history

Salient Features

• Fertilizer dose is calculated based on nutrient removal per unit yield
• Emphasizes maintenance of soil nutrient reserves
• Often used in long-term fertility management studies

Merits

• Maintains long-term nutrient balance in soil
• Useful for intensive and multiple cropping systems
• Simple and easy to understand
• Helps prevent nutrient mining of soil

Limitations

• Ignores native soil nutrient supply
• Does not consider: Soil nutrient fixation, Nutrient losses
• Risk of nutrient accumulation or depletion if removal estimates are inaccurate
• Less precise than soil test–based or STCR approaches

VI) Integrated Nutrient Management (INM) Approach

• Meaning: INM involves the judicious and combined use of: Chemical fertilizers, Organic manures (FYM, compost, green manure), Biofertilizers
• Concept: No single nutrient source can sustain productivity alone. Combines quick nutrient supply (fertilizers) with long-term soil health improvement (organics)

Salient Features

• Supplies macro-, secondary-, and micronutrients
• Improves nutrient availability through biological activity
• Reduces chemical fertilizer requirement without yield loss

Merits

• Improves:
  • Soil physical properties (structure, water holding)
  • Soil chemical properties (CEC, pH buffering)
  • Soil biological properties (microbial activity)
• Enhances nutrient use efficiency (NUE)
• Reduces environmental pollution
• Promotes sustainable and eco-friendly agriculture
• Strongly recommended by ICAR

Limitations

• Requires careful planning and technical knowledge
• Limited availability of organic manures in some areas
• Nutrient content of organics is variable
• Nutrient release from organics is slow and climate-dependent

VII) Site-Specific Nutrient Management (SSNM)

Meaning: Fertilizer recommendation tailored to individual field conditions, Unlike blanket recommendations, it considers within-field variability

Factors Considered

• Soil fertility status
• Crop nutrient demand at different growth stages
• Yield potential of the field
• Previous crop and management history

Salient Features

• Dynamic and adaptive nutrient management
• Fertilizer doses vary with crop stage and site conditions
• Widely used in precision agriculture

Merits

• High fertilizer use efficiency
• Reduces nutrient losses through leaching and volatilization
• Improves crop yield and profitability
• Avoids over- or under-fertilization
• Ideal for technology-driven farming systems

Limitations

• Requires: Technical skill, Monitoring tools (soil tests, sensors, GPS)
• High initial cost
• Less suitable for small and marginal farmers without support

VIII) Plant-Based Fertilizer Recommendation

Meaning; Fertilizer recommendation based on plant indicators rather than soil tests, Diagnoses nutrient status from plant colour, tissue composition, or sap

Common Methods

• Leaf Colour Chart (LCC) – mainly for nitrogen
• Plant tissue analysis
• Rapid tissue tests

Salient Features

• Provides real-time nutrient diagnosis
• Reflects actual nutrient uptake by the plant
• Mainly used for nitrogen management, especially in rice

Merits

• Instant and field-level decision-making
• Reduces excess nitrogen application
• Improves nitrogen use efficiency
• LCC is: Low-cost, Simple, Farmer-friendly
• Widely adopted in rice cultivation