Adaptation of two Azolla species in a laterite zone of West Bengal.
The dual effect of Azolla culture in enriched water for stripping nutrients from the medium and thus reducing water pollution has provided the ability of mass production of inoculum for utilization as a biofertilizer. The biomass production of A. mexicana and A. filiculoides was related with the variation of seasonal factors and enrichment of different water bodies receiving run-off from urban area (UR), rural area (RR), agricultural field (AR), rice mill (RMR) and a forest cover (FR) in a laterite zone of Birbhum, West Bengal (India). The general trend of nutrient enrichment was in the order of RMR, UR, AR, RR and FR. Highest productivity of A. mexicana (3.99 g/m2 per day) and A. filiculoides (4.95 g/m2 per day) was noted during October-December after culturing in AR and UR respectively followed by February-March and July-September. During that season total N (mg/litre) and total P (mg/litre) of the media were 1.11 and 3.75 respectively in AR and 0.99 and 5.69 respectively in UR. A. filiculoides showed better performance over A. mexicana in relation to biomass production, nitrogen fixation and tissue P concentration irrespective of any season. A. mexicana however concentrated more potassium.