🎒 Yield Gap Analysis

This lesson builds core elective concepts in BSc Agriculture with practical applications and exam-oriented clarity.

---

Yield Gap Analysis

Yield gap is the difference between the potential yield achievable under optimal conditions and the actual yield realised by farmers. Understanding and closing yield gaps is critical for improving food security without expanding cultivated area.

Yield Definitions

Yield Level	Definition	Determined By
Potential yield (Yp)	Maximum yield under optimal management with no biotic/abiotic stress	Solar radiation, temperature, CO2, genotype
Water-limited yield (Yw)	Yield limited only by water supply (rainfed conditions)	Yp factors + rainfall, soil water holding capacity
Actual yield (Ya)	Yield obtained by farmers in their fields	All constraints — pests, nutrients, management, socioeconomic
Exploitable yield	Achievable target — typically 80% of Yp or Yw	Best farmer practices under local conditions

Yield Gap Components

• Yield Gap I = Yp - Yw (water limitation gap)
• Yield Gap II = Yw - Ya (management gap due to nutrients, pests, weeds, sub-optimal practices)
• Technology gap = research station yield - farmer yield
• Extension gap = demonstration plot yield - farmer yield

Constraint Analysis

Major constraints contributing to yield gaps in India:

• Abiotic — drought, heat stress, soil salinity, waterlogging, nutrient deficiency
• Biotic — pests, diseases, weeds, nematodes
• Management — late sowing, sub-optimal plant population, imbalanced fertilisation, poor irrigation scheduling
• Socioeconomic — lack of credit, small farm size, limited access to quality inputs, knowledge gaps

Model-Based Diagnosis

Crop simulation models provide a powerful framework for yield gap analysis:

• Step 1 — Simulate Yp using long-term weather data and optimal management
• Step 2 — Simulate Yw by removing irrigation (rainfed scenario)
• Step 3 — Compare simulated yields with actual farmer yields from surveys or crop-cutting experiments
• Step 4 — Conduct sensitivity analysis to identify which constraints most reduce yield

Example: Wheat Yield Gap in Punjab

Parameter	Value
Simulated Yp	6.8 t/ha
Simulated Yw	5.5 t/ha
Actual farmer yield	4.5 t/ha
Yield Gap I (water)	1.3 t/ha
Yield Gap II (management)	1.0 t/ha
Total yield gap	2.3 t/ha (34%)

Global Yield Gap Atlas (GYGA)

The Global Yield Gap Atlas (www.yieldgap.org) is an international initiative that:

• Maps yield gaps for major crops across countries
• Uses consistent methodology with local weather, soil, and management data
• Identifies regions with the largest exploitable yield gaps
• Supports policy decisions on food security investment priorities

Strategies for Closing Yield Gaps

• Improved varieties — drought-tolerant, disease-resistant, high-yielding cultivars
• Precision nutrient management — soil test-based fertilisation, site-specific recommendations
• Water management — micro-irrigation, deficit irrigation scheduling, rainwater harvesting
• Timely operations — optimal sowing window, timely weed and pest management
• Knowledge transfer — extension services, demonstration plots, ICT-based advisory

Yield gap analysis provides the evidence base for targeting interventions where they can have the greatest impact on food production.

---

Summary Cheat Sheet

Topic	Key takeaway
Main focus	Yield Gap Analysis — potential vs actual yield, constraint analysis, model-based diagnosis, and strategies for closing yield gaps.
Section context	Revise this lesson with the rest of System Simulation and Agro-Advisory for stronger conceptual continuity.