Traditional Pokkali Rice–Prawn Rotation Found Essential to Prevent Soil Degradation, Study Warns
KOCHI, Kerala, India — A scientific study on the unique Pokkali wetlands of Kerala has found that continuous year-round prawn farming significantly degrades soil quality compared to the traditional Pokkali rice–prawn rotational farming system, reinforcing the need to conserve one of the world's oldest climate-resilient farming practices.
Researchers from Kerala Agricultural University evaluated soils under three land-use systems—traditional rice–prawn rotation, rice-only cultivation, and prawn-only farming—in major Pokkali regions of Ernakulam. Their findings indicate that fields maintained exclusively for prawn culture showed declining soil health across several important indicators.
The study found that soils under year-round prawn farming had the **highest electrical conductivity**, indicating greater salt accumulation, the **highest bulk density**, suggesting increased soil compaction, and the **lowest soil organic carbon**, a critical measure of long-term soil fertility. Microbial biomass carbon, an indicator of beneficial soil microbial activity, was also lowest in prawn-only fields.
In contrast, the traditional Pokkali rice–prawn rotational system demonstrated the best overall soil quality. The rotational fields recorded the lowest bulk density, the highest organic carbon content, and the greatest microbial biomass, reflecting healthier and more biologically active soils capable of sustaining long-term agricultural productivity.
Although prawn monoculture can generate attractive short-term financial returns, the researchers caution that continuous monoculture may gradually reduce soil quality, making the production system less sustainable over time.
"Pokkali wetlands are unique ecological systems where seasonal rice cultivation naturally complements prawn farming," the researchers noted. "Maintaining the traditional rotation helps preserve soil fertility while protecting the ecological balance of these valuable coastal wetlands."
The study also observed that all three land-use systems maintained near-neutral soil pH, but the rotational system consistently outperformed prawn-only farming in most indicators of soil health. Statistical analysis confirmed significant differences among the different farming systems.
Kerala's Pokkali ecosystem, located mainly across Ernakulam, Alappuzha, and Thrissur districts, is internationally recognized for its salt-tolerant Pokkali rice varieties and traditional organic rice–fish farming. Besides producing nutritious rice and premium prawns, the ecosystem supports biodiversity, acts as a natural buffer against saline intrusion, and contributes to climate resilience in coastal regions.
Researchers conclude that protecting the traditional rice–prawn rotational farming system is essential for conserving the long-term productivity of Pokkali wetlands. They recommend discouraging permanent conversion of Pokkali fields into year-round prawn monoculture and instead promoting integrated organic rotational farming that sustains both agricultural production and ecosystem health.
The findings add scientific evidence to ongoing conservation efforts aimed at safeguarding Kerala's Pokkali heritage, emphasizing that maintaining the traditional seasonal balance between rice and prawn cultivation remains the most effective strategy for preserving soil health and ensuring sustainable use of these globally significant coastal wetlands.
Reference: Characterisation of different land uses in Pokkali ecosystem. Global Symposium on Salt-Affected Soils. 20-22 October 2021.
