Probiotic-assisted bioconversion of agro-waste into organic liquid NPK fertilizer: Fermentation dynamics and efficacy evaluation on paddy under pot and field conditions

Using factorial combination of nitrogen (poultry litter, greengram flour, groundnut cake), phosphorus (rock phosphate, PROM, bone meal) and potassium-rich (potassium humate, wood ash, pressmud) agro-residues, a total of 27 treatments were developed along with two controls (absolute and chemical). Probiotic strains including Lactobacillus spp. and Saccharomyces spp (extracted from milk and bread) were subjected to co-fermentation with Azospirillum, phosphate-solubilizing bacteria (PSB), and potassium-mobilizing bacteria under aerobic conditions for 30 days at optimum temperature of 30 ± 2 °C and pH 6.5-7.5. The formulation containing groundnut cake + rock phosphate + potassium humate recorded the highest NPK content of 15% along with the presence of important metabolites like indole-3-acetic acid (IAA), gibberellic acid, cellulase and phosphatase. Through a three-month rice cycle of field evaluation, the treatment (T21) containing 50% organic NPK liquid fertilizer along with 50% RDF observed to significantly enhanced the height of the plant (90.6 cm), tillering (15 tillers/plant) and grains (125 grains/panicle) as compared to control and chemical fertilizer alone. Using agro-waste will definitely valorise crop production in a sustainable way by reducing the dependency on chemical inputs.