Development of Fly Ash based Blue Green Algal Inoculants for Rice Crop Production

Abstract

Seven filamentous heterocystous region specific blue green algae were isolated from rhizospheric zone of paddy field soil and pond flyash and were identified as Calothrix sp., Anabaena flos-aquae, Desmonostoc sp DGRKC, Nostoc commune, Nostoc sp. PS1, Nostoc sp. DGRKF and Anabaena sp. Anabaena sp. (Isolate G) showed maximum dry biomass production by 3.45 mg/mL and Desmonostoc sp DGRKC (Isolate C) showed highest nitrogenase activity (32.2 ƞmole C2H4/mg dry wt/hr), total nitrogen content (0.127 %), heterocyst frequency (18.2%) and nitrate reductase activity (31.0162 µmole NO-2). Anabaena flos-aquae (Isolate B) showed maximum chlorophyll content (3.79 µg/ml), nitrate reductase activity (27.62 µmole NO-2) and nitrogenase activity by 20.31 ƞmole C2H4/mg dry wt/hr. Fly ash showed high thermal stability with least weight loss as observed in TGA and SEM graph indicated that flyash is composed of spherical structures with more surface area for interaction. XRD and EDS studies showed that amorphous content of ash consists of calcium oxide, potassium and major crystalline phases observed were quartz (SiO2) and aluminium silicon oxide (Al4.52Si1.48) and haematite (Fe2O3). Charcoal, was amorphous in nature consisting of carbon and graphite. Soil and montmorillonite showed similar results in XRD, FTIR and thermal analysis revealed porous nature with silica as major constituent. The impact of consortium of filamentous nitrogen fixing cyanobacteria comprising Anabaena variabilis, Aulosira fertilissima, Nostoc muscorum and Tolypothrix tenuis inoculants on different rice cultivars (PUSA 1121, PR 118, PAU 201, SHABNAM and BASMATI 1401improved the grain yield of rice over a period of three years by 8qtl/ha for Basmati 1407 and 5qtl/ha for SHABNAM and PUSA 1121 as compared to urea alone and control, whereas flyash based cyanobacterial biofertilizer (BGA) application alone showed increase by 6 qtl/ha for rice variety BASMATI 1401 followed by 4 qtl/ha for PUSA1121 and by 3 qtl/ha for PR118 and SHABNAM. Increase in crop yield by 2-6 qtl/ha over control among all rice cultivars supports a positive role of fly ash based algal biofertilizers in soil is consistent with diazotrophic potential of the cyanobacterial strains used. There was an increase in soil organic carbon from 0.32 to 0.53 %, total nitrogen from 0.042 to 0.067 % and phosphorus content from 7.9-27.70 mg/kg as a result of application of cyanobacterial biofertilizers. Fly ash based algal biofertilizers makes rice production system more viable and reduces the ecological hazards caused due to synthetic fertilizers which can serve as an important component of the integrated plant nutrient supply system with net savings in urea by 15-35 %.