Role of cyanobacteria on rice field soil fertility of Bangladesh

The present work was undertaken to study the qualitative and quantitative distribution of indigenous cyanobacteria including eukaryotic algae in 44 rice fields of 11 representative districts of Bangladesh and to evaluate their relationship with soil fertility variables. The variation in cyanobacterial population in soil assessed by single correlation study reveals that the abundance of cyanobacterial population is positively and significantly related to pH, available P and available S while negatively but significantly to total N contents of the soils.Results of field experiments a suggest that addition of N (0,60,120 N ha-1 as urea) alone suppressed the growth of indigenous cyanobacteria while P- fertilization (0, 30, 60 kg P ha-1) alone and in conjunction with nitrogen (N60P60) encouraged the propagation of cyanobacteria significantly reflecting the fact that supply of P could overcome the depressive impact of N- fertilizer and thereby flourishing and stimulating the abundance of the concerned cyanobacteria in the rice field ecosystem.Yield of rice grain was recorded to be better in the plot showing higher concentration of cyanobacteria encouraged by P- fertilization.