Dr. Sabyasachi Karak
Introduction: A Regenerative Pathway for Modern Agriculture
Contemporary agriculture is confronted with intertwined crises of soil degradation, declining nutrient availability, and climate instability. Globally, nearly one-third of the world’s soils are moderately to highly degraded due to erosion, nutrient mining, and excessive reliance on agrochemicals (FAO, 20211). These trends threaten food security, rural livelihoods, and long-term ecological stability.
Amidst these challenges, green manure, often referred to as nature’s fertilizer, has re-emerged as a scientifically robust, climate-smart, and ecologically grounded soil restoration practice. Beyond serving as an organic nutrient source, green manure embodies a shift from chemical-centric farming to a holistic, ecosystem-based approach. As Pretty et al. (20182) observe, sustainable intensification today requires redesigning agricultural systems where soil is treated as a living organism rather than an inert platform for crops.
What is Green Manure? Nature’s Soil Doctor
Green manure consists of crops grown specifically for soil enrichment rather than for harvest. Common species include Sesbania aculeata (dhaincha), Crotalaria juncea (sunn hemp), Vicia sativa (vetch), and Trifolium repens (white clover). These crops are typically incorporated into the soil at the pre-flowering stage, when biomass quality and nutrient concentrations peak.
Functionally, green manure acts as a biological nutrient pump, capturing atmospheric nitrogen, recycling residual nutrients, and enhancing soil organic matter. Leguminous varieties are especially potent, fixing 40-200 kg N/ha, thereby reducing dependence on synthetic fertilizers (Kumar et al., 2019; Lal, 202034).
How Green Manure Works
- Cultivation: Sown during fallow windows or between crop cycles.
- Incorporation: Biomass is ploughed into the soil before flowering.
- Decomposition: Soil microbes mineralize plant material, releasing nutrients.
- Soil Enrichment: Subsequent crops benefit through increased fertility, enhanced moisture retention, and improved microbial activity.
Agroecological Benefits and Soil Restoration Functions
- Soil Fertility Enhancement: Green manure significantly improves soil nutrient status through biological nitrogen fixation facilitated by symbiotic Rhizobium in root nodules (Ghosh & Bhat, 20195).
- Improved Soil Structure and Water Dynamics: Green manure promotes aggregate stability, porosity, and water infiltration, reducing erosion and enhancing climate resilience (ICAR, 20226).
- Natural Suppression of Pests, Diseases, and Weeds: Species such as mustard release allelopathic compounds that suppress weeds and inhibit pathogens (Cherr et al., 20067).
- Biodiversity and Pollinator Support: Flowering species enhance habitat for pollinators and beneficial insects (Altieri & Nicholls, 20208).
- Pollution Control and Phytoremediation: Certain species absorb excess nutrients and contaminants, reducing water pollution (Zhao et al., 20219).
Applications in Integrated Farming and Scientific Evidence
Long-term studies show that continuous use of green manure maintains crop yields while reducing synthetic nitrogen fertilizer use by 20-30% (Rao et al., 202010). Smallholders benefit from low-cost organic matter availability, improved vegetable production, and nutrient recycling (Pretty et al., 2018). Research by ICAR (2022) also indicates enhanced microbial biomass carbon in rice-wheat systems after green manure integration.
Lifecycle of Green Manure
- Selection of species.
- Sowing in off-season or intercrop.
- Growth until nutrient peak.
- Incorporation into 15-20 cm soil layer.
- Transition to nutrient-demanding crops.
Limitations and Considerations
- Timing of incorporation.
- Species suitability.
- Labour and seed cost.
- Moisture requirements for decomposition.
Benefits of Green Manure in Sustainable Farming
Green manure plays an essential role in advancing sustainable agriculture by strengthening soil health, enhancing ecological stability, and reducing the dependence on synthetic inputs. When incorporated into the soil, green manure enriches organic matter, restores soil structure, and encourages the natural cycling of nutrients, particularly nitrogen fixed by leguminous species. This gradual and biologically mediated nutrient release supports long-term fertility while lowering production costs for farming households. Moreover, green manure improves soil moisture retention and aggregate stability, enabling farms to better withstand droughts and extreme rainfall events. From an ecological standpoint, it contributes to increased biodiversity both above and below the soil surface by creating favorable conditions for beneficial insects, pollinators, microbes, and earthworms. As a result, green manure strengthens the overall resilience and productivity of agroecosystems while promoting an environmentally responsible farming approach.
Green Manure Impacts on Climate Change
Green manure contributes significantly to both climate change mitigation and adaptation, making it a cornerstone of climate-smart agriculture. By adding substantial organic biomass to the soil, green manure enhances carbon sequestration, increasing soil organic carbon levels and reducing atmospheric CO₂. This build-up of carbon-rich organic matter also supports improved soil structure, which lowers erosion and enhances water infiltration, critical for buffering farms against climate-induced stresses such as droughts and erratic rainfall. Additionally, by improving nitrogen efficiency in cropping systems, green manure reduces the need for synthetic fertilizers whose production and application are major sources of greenhouse gas emissions, particularly nitrous oxide (N₂O). The cumulative effect is a reduction in the carbon footprint of farming while simultaneously strengthening the resilience of soils, crops, and farming communities against the impacts of a changing climate.
Conclusion
Adopting green manure is not merely a technical intervention; it is a movement toward ecological restoration and rural resilience. By improving soil fertility, enhancing water efficiency, supporting biodiversity, and reducing emissions, green manure embodies the principles of climate-smart agriculture.
As India transitions toward low-carbon, regenerative farming, green manure offers a practical pathway that merges traditional ecological knowledge with modern sustainability science. By embracing this “green gold,” farmers can rejuvenate their soils, safeguard livelihoods, and contribute meaningfully to the global fight against climate change.
“Turn your soil into green gold, restore its life, secure the planet’s future”
