Cyanobacteria from paddy fields in Iran as a biofertilizer in rice plants

Cyanobacteria were isolated, identified, multiplied and used as an inoculum in pot rice experiment. The pH, moisture and algal population were measured in four seasons. The highest and lowest pH (6.7, 6.2), moisture of soil (43%, 34%) and algal population (12, 20 colony-forming units/50 mL on A and B medium and 4, 5 colony-forming units/50 mL on A and B medium) were recorded in spring and winter, respectively. The only heterocystous cyanobacteria found in soil samples were identified as Anabaena with four species as follows: A. spiroides, A. variabilis, A. torulosa and A. osillarioides. The germination of rice seeds treated with cyanobacteria was faster than that of controls. The results of pot experiments were as follows: increase of 53% in plant height; 66% in root length; 58% in fresh leaf and stem weight; 80% in fresh root weight; 125% in dry leaf and stem weight; 150% in dry root weight; 20% in soil moisture; 28% in soil porosity and a decrease of 9.8% in soil bulk density and 4.8% in soil particle density. There were significant differences between pots treated with cyanobacteria and control samples.