Symbiotic Blue Green Algae (Azolla): A Potential Bio fertilizer for Paddy Rice Production in Fogera Plain, Northwestern Ethiopia
A field experiment was carried out in Fogera plain, where lowland rice is widely grown, to assess the adaptability and yield of Azzola strains and to determine the level of nitrogen they generate in 2005 and 2006. A year earlier, 2004, the two Azolla strains (Azolla filiculoides and Azolla microphylla) were introduced from India. They were maintained and multiplied in plastic containers at Adet in a greenhouse and then inoculated into concrete tanks for testing their adaptability. Both strains were well adapted to Adet condition. The actual experiment was laid out in a randomized complete block design replicated three times. In the summer season, Azolla filiculoides gave an average of 48 tons/ha (range: 42-56.4 tons) and Azolla microphylla yielded 40 tons/ha fresh biomass (range: 30-45 tons). In autumn and winter seasons, biomass production was reduced because of fluctuating temperatures. An average of 54.4 t ha-1 of Azolla fresh biomass was harvested at Fogera. Maximum plant height, number of tillers, straw yield and grain yield of rice was recorded on the treatment that was planted by using 64 kg N + 20 kg P ha-1 followed by Azolla filiculoides + 20 kg P ha-1, 32 kg N + 10 kg P ha-1. Inoculation of Azzola by incorporating once into the soil has increased rice yield by 911 kg ha-1 (19%) on Azolla filiculoides plots and 721 kg ha-1 (15%) on Azolla microphylla plots. However, there was temperature fluctuation and colonization of Azolla roots by algae. Multiplication and maintenance of Azolla needs special attention. It also needs continuous watering to a depth of 5 -10 cm and P fertilizer application, thus, irrigation facility and alternate P sources are vital. Azolla gives a lot of biomass and it is easy to manage and establish, which means that it is logical and cost-effective to use it as biofertilizer for paddy rice. Its effect on high value and perennial crops may be the subject of further research.
Keywords: Azolla, biofertilizer, fresh biomass, nitrogen, rice, symbiotic