Nostoc commune Vauch and Azolla pinnata R. Br. fertilized with phosphorus, iron and molybdenum and their effects on wetland rice

Laboratory experiments were done to determine the levels of phosphorus, iron and molybdenum that would support the best growth and nitrogen fixing capacity for Nostoc commune and Azolla pinnata. Results obtained for N. commune were 20, 10 and .002 ppm for phosphorus, iron and molybdenum, while for A. pinnata, the levels were 30, 20 and .002 ppm, respectively. The biomass of N. commune and A. pinnata had an initial decrease in weight at the first sampling period (20 DAT). After this, an increase in biomass was observed until 60-80 DAT and in most treatments biomass declined at harvest time. Orthophosphate levels of floodwater gradually decreased from 0 DAT [days after treatment] until harvest time. As biomass increased, the ammonium nitrogen content of floodwater, likewise, increased. Iron levels generally also increased until harvest time period. In all the treatments tested, it has been observed, too, that the levels of these three nutrients were higher in pots given with P, Fe, and Mo. Three vegetative parameters of the growth of rice namely plant height, tiller number and leaf area were measured. In the experiment, these three parameters were observed to be higher in treatments with P, Fe and Mo. Leaf area, however, did not yield statistically significant results. More panicles were obtained in Nostoc and Azolla treated plants. While the least number of panicles was observed in treatments without the alga, azolla, urea, or P, Fe, Mo fertilization. More field grains per plant were counted in azolla and alga treated plants. These results were comparable to those obtained for urea indicating the effectiveness of Nostoc and Azolla as bio-fertilizers for rice. The same trend was observed for the grain yield. Nitrogen content in the rice tissues treated with Azolla, Nostoc or urea was higher compared to the control rice plants which had a very small amount of nitrogen in their tissues.