Strategic valorization of de-oiled microalgal biomass waste as biofertilizer for sustainable and improved agriculture of rice (Oryza sativa L.) crop.

Intensive use of chemical fertilizer results in environmental pollution that disturbs the local ecosystem and causes reduction in the long-term crop yield. There is a need to explore the alternative source of plant nutrition such as de-oiled microalgal biomass as biofertilizer for sustainable production of food crops in a relatively pollution free environment. This study reports sustainable and improved agriculture of rice crop (cv. IR 36) by valorizing de-oiled microalgal biomass waste (DOMBW) of Scenedesmus sp., as eco-friendly fertilizer. The microalga (MA) was cultivated in open raceway pond using wastewater and flue gas. Performance evaluation and comparison of DOMBW with respect to growth and yield of rice plants vis-à-vis commercial chemical fertilizers (CF) and vermicompost (VC) applied individually or together, established the superiority of the former. The experiment comprised of five nutrient management treatments (CF100, VC100, MA100, MA50+CF50, and MA50+VC50) meeting 100% nitrogen (N) recommendation either through a single source or combined application in the soil. Combining the application of microalgal based organic fertilizer with chemical fertilizer (MA50+CF50), showed the highest performance in terms of plant height, tiller number, biomass, and grain yield. At the harvest stage, MA50+CF50 also resulted in maximum plant dry weight, panicle weight, and 1000-grain weight in comparison to other treatments. This study revealed that the application of DOMBW as a biofertilizer is potentially sustainable and effective in improving the yields of rice crop with reduced use of chemical fertilizer.