Role of blue green algae biofertilizer in ameliorating the nitrogen demand and fly-ash stress to the growth and yield of rice (Oryza sativa L.) plants

Rice is a major food crop throughout the world; however, accumulation of toxic metals and metalloids in grains in contaminated environments is a matter of growing concern. Field experiments were conducted to analyze the growth performance, elemental composition (Fe, Si, Zn, Mn, Cu, Ni, Cd and As) and yield of the rice plants (Oryza sativa L. cv. Saryu-52) grown under different doses of fly-ash (FA; applied @ 10 and 100 t ha−1 denoted as FA10 and FA100, respectively) mixed with garden soil (GS) in combination with nitrogen fertilizer (NF; applied @ 90 and 120 kg ha−1 denoted as NF90 and NF120, respectively) and blue green algae biofertilizer (BGA; applied @ 12.5 kg ha−1 denoted as BGA12.5). Significant enhancement of growth was observed in the plants growing on amended soils as compared to GS and best response was obtained in amendment of FA10 + NF90 + BGA12.5. Accumulation of Si, Fe, Zn and Mn was higher than Cu, Cd, Ni and As. Arsenic accumulation was detected only in FA100 and its amendments. Inoculation of BGA12.5 caused slight reduction in Cd, Ni and As content of plants as compared to NF120 amendment. The high levels of stress inducible non-protein thiols (NP-SH) and cysteine in FA100 were decreased by application of NF and BGA indicating stress amelioration. Study suggests integrated use of FA, BGA and NF for improved growth, yield and mineral composition of the rice plants besides reducing the high demand of nitrogen fertilizers.