Nutrient and Organic Fertility Characteristics of Pokkali Farm Clay Soil
Pokkali farm soils are acid saline clay soils formed in the tidal wetlands of coastal Kerala and are naturally enriched with organic matter and mineral nutrients through periodic tidal deposition and organic recycling. Rice-Prawn rotational farming clay soil exhibits superior fertility characteristics compared with year round prawn-only systems.
Key fertility features
Clay texture: The soil possesses a heavy clay texture, which provides a high capacity to retain nutrients, moisture, and organic matter, making it inherently fertile.
Near-neutral reaction: Soil pH remained close to neutral (around 6.9), a favorable range for nutrient availability and microbial activity.
Low to moderate salinity: Electrical conductivity was below 4 dS m⁻¹, indicating that the rotational fields maintained salinity within a manageable range for crop growth.
High organic carbon: The rice–prawn clay soil recorded 1.64% soil organic carbon, reflecting substantial organic matter accumulation from rice residues, aquatic biomass, and organic farming practices.
Low bulk density: A bulk density of 0.684 Mg m⁻³ indicated a loose, well-aggregated soil with better aeration and root penetration.
Rich microbial biomass: Microbial biomass carbon reached about 250 µg g⁻¹ soil, suggesting an active microbial community that supports nutrient cycling and organic matter decomposition.
Good biological activity: The soil exhibited strong dehydrogenase activity, confirming active microbial metabolism and overall soil biological health.
These characteristics indicate that Pokkali clay soils function as nutrient-rich, organically fertile wetland soils capable of sustaining crop production with minimal external inputs. The combination of high organic carbon, strong microbial activity, and high nutrient-holding capacity makes the traditional Pokkali rice–prawn rotation an effective system for maintaining long-term soil fertility and ecological stability.
In contrast, soils under year-round prawn monoculture showed:
lower organic carbon,
reduced microbial biomass,
higher soil compaction,
and greater salt accumulation,
demonstrating a gradual decline in soil fertility and highlighting the importance of preserving the traditional rotational farming system for sustainable management of Pokkali wetlands.
Key fertility features
Clay texture: The soil possesses a heavy clay texture, which provides a high capacity to retain nutrients, moisture, and organic matter, making it inherently fertile.
Near-neutral reaction: Soil pH remained close to neutral (around 6.9), a favorable range for nutrient availability and microbial activity.
Low to moderate salinity: Electrical conductivity was below 4 dS m⁻¹, indicating that the rotational fields maintained salinity within a manageable range for crop growth.
High organic carbon: The rice–prawn clay soil recorded 1.64% soil organic carbon, reflecting substantial organic matter accumulation from rice residues, aquatic biomass, and organic farming practices.
Low bulk density: A bulk density of 0.684 Mg m⁻³ indicated a loose, well-aggregated soil with better aeration and root penetration.
Rich microbial biomass: Microbial biomass carbon reached about 250 µg g⁻¹ soil, suggesting an active microbial community that supports nutrient cycling and organic matter decomposition.
Good biological activity: The soil exhibited strong dehydrogenase activity, confirming active microbial metabolism and overall soil biological health.
Fertility implication
These characteristics indicate that Pokkali clay soils function as nutrient-rich, organically fertile wetland soils capable of sustaining crop production with minimal external inputs. The combination of high organic carbon, strong microbial activity, and high nutrient-holding capacity makes the traditional Pokkali rice–prawn rotation an effective system for maintaining long-term soil fertility and ecological stability.
Year-round Prawn Farming destroying Pokkali Soil Fertility
In contrast, soils under year-round prawn monoculture showed:
lower organic carbon,
reduced microbial biomass,
higher soil compaction,
and greater salt accumulation,
demonstrating a gradual decline in soil fertility and highlighting the importance of preserving the traditional rotational farming system for sustainable management of Pokkali wetlands.
Characterization of Pokkali Farm Clay Soil