Combined influence of blue green algae and azolla on dissolved oxygen, redox status and methane emission potential of systems of rice cultivation

Blue Green Algae and Azolla are aerobic photosynthetic organisms. In the medium of their growth, they release a lot of O2 during photosynthesis. As a result, when they grow in rice fields they make the standing water highly oxygenated. Its directly influence the dissolved oxygen and redox potential ultimately reduces the emission of methane from rice filed. The field experiment was conducted at Ponnaniar Basin, Thirchirapalli District, Tamil Nadu, India in rabi season of 2013. Redox status of soil and dissolved oxygen content in the standing water are indirect indicators of methane flux from rice ecosystem and higher the redox and dissolved oxygen, lower would be the methane flux. Among the different systems of rice cultivation, System of Rice Intensification recorded higher dissolved oxygen and redox potential than other cultivation systems. BGA and Azolla application individually and in combination enhanced the dissolved oxygen concentration and redox in the standing water in all growth stages while the dissolved oxygen concentration was minimum in plots applied only with recommended dose of fertilizer. The mean methane flux in only fertilizer applied plot was higher, while the flux was reduced to 22.3 per cent, due to application of BGA and Azolla.