Open Agriculture. 2018; 3: 478–489 mode of application of microbial inoculants in influencing plant growth and rhizospheric metabolic activities. Keywords: biofilms; nutrient availability; microbial activity; plant growth; soil drench 1 Introduction Plants and microbes are known to communicate through transkingdom signalling systems, which occur during different stages of development, and most of the research has focussed on the physical, biochemical and ecological characteristics of the rhizosphere (Lugtenberg et al. 2002). It has been estimated that around 20-40% of the photosynthetically fixed carbon is given out in the form of root exudates; this excess emphasizes the relevance assigned by the plant to support the establishment of beneficial microbial communities and interact with them for better water and nutrient availability (Aira et al. 2010; Bais et al. 2006). Crops require requisite nutrients to sustain growth, reproduce and produce high quality grains or flowers or fruits. Fertility management of flower crops is particularly expensive as they are heavy consumers of fertilizers, particularly K/N ratios which improve photosynthetic canopy, after first flush, and stimulate the next flowering event. Chrysanthemum is an important commercial flower crop, which is exacting in its nutritional requirements and day length control, and needs to be supplied with a healthy mix of macro and micronutrients (Handreck and Black 1994). Among plant growth promoting (PGP) bacterial inoculants which are used for biofertilization, phytostimulation and biocontrol, cyanobacteria have become important inputs (Mandal et al. 1999; Gupta et al. 2013; Velmourougane et al. 2017); from their traditional https://doi.org/10.1515/opag-2018-0053 received July 6, 2018; accepted October 16, 2018 Abstract: Availability of nutrients in soil plays an important role in the productivity and quality of flowers in chrysanthemum. A set of novel biofilm inoculants- Anabaena-Azotobacter, Anabaena-Pseudomonas fluorescens (An-Psf) and Anabaena-Trichoderma (An-Tr) were applied as carrier based dry formulation or soil drench and their performance compared in two varieties of chrysanthemum (White Star and Zembla), in a climate- controlled greenhouse. Both the An-Psf and (An-Tr) inoculants enhanced glomalin related soil proteins in the rhizosphere of White Star, while in terms of polysaccharide content of soil, both these inoculants performed better in Zembla variety. Significant increases in the availability of selected macro and micronutrients in rhizosphere soil samples, in both chrysanthemum varieties were recorded, particularly when the inoculants were applied as soil drench. Principal Component analysis illustrated the significant interaction among soil and plant parameters, more specifically, the distinct effect of the inoculants, as compared to the application of carrier alone or control treatment. This investigation demonstrated the varietal effects on soil biological activities and significance of Research Article Radha Prasanna, Garima Saxena, Babita Singh, Kunal Ranjan, Rishi Buddhadeo, Kulandaivelu Velmourougane, Balasubramanian Ramakrishnan, Lata Nain Mode of application influences the biofertilizing efficacy of cyanobacterial biofilm formulations in chrysanthemum varieties under protected cultivation *Corresponding author: Radha Prasanna, Division of Microbiology, ICAR- Indian Agricultural Research Institute, New Delhi 110012, India, E-mail: radhapr@gmail.com Garima Saxena, Babita Singh, Kunal Ranjan, Rishi Buddhadeo, Ku- landaivelu Velmourougane, Balasubramanian Ramakrishnan, Lata Nain, Division of Microbiology, ICAR- Indian Agricultural Research Institute, New Delhi 110012, India Mam Chand Singh, Murtaza Hasan, Centre for Protected Cultivation Technology (CPCT), ICAR-Indian Agricultural Research Institute, New Delhi 110012, India Yashbir Singh Shivay, Division of Agronomy, ICAR- Indian Agricultu- ral Research Institute, New Delhi 110012, India Open Access. © 2018 Radha Prasanna et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution- NonCommercial-NoDerivs 4.0 License.