🎒 Water and Soil Management for Climate Resilience

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

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Water and Soil Management for Climate Resilience

Water Management as Adaptation

Water is the most critical resource threatened by climate change. Erratic rainfall, increased evapotranspiration, and groundwater depletion demand efficient water management strategies.

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System of Rice Intensification (SRI)

SRI is a set of management principles that dramatically improve rice productivity while reducing water consumption:

Key SRI Principles

1. Young seedling transplanting: 8–12 days old (vs 21–30 days in conventional)
2. Single seedling per hill: One plant instead of 2–4
3. Wider spacing: 25×25 cm or 25×30 cm grid pattern
4. Intermittent irrigation: Soil kept moist but not flooded; water applied when soil shows hairline cracks
5. Organic matter addition: Compost or FYM application
6. Mechanical weeding: Rotary weeder used 2–3 times

SRI Outcomes

• Water saving: 25–50% reduction in irrigation water compared to continuous flooding
• Yield increase: 20–30% higher yields in most field trials
• Reduced CH₄: Less anaerobic condition → lower methane emissions
• Root development: Better root architecture in aerobic conditions

Adoption

• Practiced in 50+ countries; India, Indonesia, Cambodia, Madagascar, Ethiopia
• Supported by ICAR and state agriculture departments in India

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Alternate Wetting and Drying (AWD)

AWD is a simplified water management technique for lowland rice:

Mechanism

• Perforated field water tubes (observation tubes) inserted in soil
• Irrigation applied only when water level in tube falls below -15 cm from soil surface (safe AWD)
• Soil alternates between flooded and aerobic conditions

Benefits

• CH₄ reduction: 30–70% less methane emission compared to continuous flooding
• Water saving: 20–25% reduction in irrigation water
• Minimal yield penalty: Yield maintained if applied at correct threshold
• N₂O note: Slight increase in N₂O under aerobic conditions but net GWP effect is still positive

AWD in India

• Demonstrated in Punjab, Haryana, West Bengal, Tamil Nadu
• Promoted through NICRA and NAIP projects
• IRRI and national NARS collaboration

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Deficit Irrigation

Deficit irrigation applies less water than full crop water requirement, deliberately allowing mild stress:

• Apply 80% of ETc (crop evapotranspiration) — threshold beyond which yield impact is minimal
• Most effective during vegetative growth stages; reproductive stages need full water
• Yield maintained stable with 20% water saving in wheat and maize under deficit irrigation
• Requires precise scheduling — based on soil moisture monitoring or crop-stage calendars
• Tools: tensiometers, capacitance sensors, scheduling apps

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Drip Irrigation

Drip irrigation delivers water directly to the root zone through emitters:

• Reduces water use by 30–50% compared to surface irrigation
• Suitable for: vegetables, sugarcane, banana, grapes, cotton
• Fertigation: Nutrients delivered through drip system — improves NUE
• India has the largest drip irrigation programme globally (>10 million ha under PM-KUSUM + PMKSY)

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Rainwater Harvesting

Capturing and storing rainwater to use during dry periods:

Farm Ponds

• Dugout structures on farms to collect runoff
• Stores water for supplemental irrigation during dry spells
• Capacity: 30,000–100,000 litres typical on-farm scale
• Subsidized under MGNREGS and PMKSY

Check Dams

• Constructed across seasonal streams to impound runoff
• Recharge groundwater and provide surface water storage
• Effective in Rajasthan, Gujarat, Maharashtra drylands

Percolation Tanks

• Shallow storage structures that promote groundwater recharge
• Reduce runoff, increase infiltration

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Soil Health as Adaptation and Mitigation

Healthy soils are simultaneously a climate adaptation tool (improved water and nutrient holding) and a mitigation tool (carbon sequestration).

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Soil Organic Carbon (SOC)

SOC is the foundation of soil health and climate resilience:

• Each 1 tonne/ha increase in SOC sequesters 3.67 tonnes CO₂ (CO₂ equivalent of carbon)
• SOC improves water holding capacity: 1% increase in SOM increases water holding by 20 litres/m³ soil
• Enhances aggregate stability, reducing erosion risk
• Improves nutrient retention and biological activity

India's SOC Status

• Most Indian soils are low in organic carbon (<0.5%)
• Sequestration potential: 39–49 Tg C/year nationally (ICAR estimates)

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Biochar

Biochar is a carbon-rich material produced by pyrolysis (thermal decomposition of biomass in low/no oxygen conditions):

Properties

• Recalcitrant carbon: Highly stable; remains in soil for 100s to 1,000s of years
• Porous structure: Improves soil water retention and aeration
• High surface area: Enhances nutrient and water holding

Benefits

• Increases SOC by 50–80% compared to uncomposted organic matter
• Improves soil water retention — important for drought-prone soils
• Reduces N₂O emissions by 10–80% from soil
• Improves germination and root growth in degraded soils

Production

• Feedstocks: Crop residues (rice husk, wheat straw), wood waste, municipal organic waste
• Temperature: 300–700°C
• Low-cost kilns available for village-level production

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Conservation Tillage

Conservation tillage minimizes soil disturbance, preserving organic matter and soil structure:

Practice	Description	SOC Impact
Zero tillage (No-till)	No ploughing; direct seeding	+15–30% SOC
Minimum tillage	Shallow cultivation only	+5–15% SOC
Strip tillage	Tillage only in seed rows	Intermediate

Benefits

• Reduces fuel consumption (saves 10–15 litres diesel/ha)
• Preserves soil moisture (less evaporation from undisturbed surface)
• Promotes earthworm populations and beneficial fungi
• Adopted on >10 million ha in Indo-Gangetic Plains (Happy Seeder technology)

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Cover Cropping

Cover crops grown in fallow periods or as intercrops:

• Legume cover crops: Sesbania, Crotalaria, Cowpea — fix N and add organic matter
• Non-legume cover crops: Oats, Rye, Sorghum-Sudan grass — biomass and erosion protection
• Improves SOC by 0.1–0.3 t C/ha/year

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Green Manuring

Green manuring involves incorporating fresh plant material into soil:

• Sesbania aculeata (Dhaincha): Most commonly used; fixes 80–100 kg N/ha; biomass up to 8 t/ha in 40–45 days
• Crotalaria juncea (Sunn hemp): Deep-rooted; good biomass; drought tolerant
• Incorporated before flowering for maximum N content
• Reduces requirement for 25–30 kg synthetic N/ha

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Crop Residue Retention

Managing crop residue after harvest:

• Surface retention: Residues left on soil surface as mulch → protects SOC, reduces erosion
• Vs burning: Burning emits CO₂, aerosols, CH₄, N₂O; destroys SOC and beneficial organisms
• Residue incorporation: Faster decomposition but some N immobilization risk

Stubble burning issue in Punjab/Haryana: 20–25 million tonnes of rice straw burned annually; contributes to air pollution and SOC loss. Alternatives: Happy Seeder (direct wheat sowing into rice stubble), biochar production, industrial use.

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Integrated Nutrient Management (INM)

INM combines organic and inorganic nutrient sources for sustained soil health:

• Replaces 25–30% of synthetic N with organic sources
• Maintains or improves SOC over time
• Reduces N₂O emissions from soil
• Components: FYM + compost + crop residues + biofertilizers + chemical fertilizers at reduced rates

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Soil Health Card (SHC) Scheme

• Launched 2015 by Ministry of Agriculture
• Farmers receive cards with soil test results for 12 parameters: NPK, pH, EC, OC, micronutrients
• Recommendations for fertilizer application based on soil test
• Over 220 million cards issued; monitoring SOC trends across India

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Irrigation Methods Comparison

Method	Water Use	Adaptation Benefit	Mitigation Benefit	Suitability
Flood irrigation	Very high	Low	None	Traditional; being phased
SRI	High (less than flood)	High	Moderate (less CH₄)	Rice in all regions
AWD	High (less than flood)	High	High (CH₄ -30%)	Lowland rice
Sprinkler	Moderate	Moderate	Low	Vegetables, groundnut
Drip	Low	High	Moderate	Horticulture, sugarcane
Deficit irrigation	Moderate	Moderate	Low	Wheat, maize
Rainwater harvesting	NA (supplemental)	Very high	Moderate	Drylands, rain-fed areas

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Key Terms

• SRI: System of Rice Intensification — management principles for water and yield efficiency
• AWD: Alternate Wetting and Drying — water management technique reducing CH₄ in rice
• Biochar: Pyrolyzed biomass; stable carbon form; improves soil health and sequesters carbon
• SOC: Soil Organic Carbon — critical measure of soil health and carbon sequestration
• INM: Integrated Nutrient Management — balanced use of organic and inorganic nutrients
• Happy Seeder: Machine that sows wheat into standing rice stubble — avoids residue burning
• ETc: Crop evapotranspiration — water use benchmark for irrigation scheduling

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Summary Cheat Sheet

Topic	Key takeaway
Main focus	SRI, AWD, deficit irrigation, rainwater harvesting, soil organic carbon, biochar, conservation tillage, and INM for climate-resilient agriculture.
Section context	Revise this lesson with the rest of Agronomic Interventions for stronger conceptual continuity.