Assessment of the biological and chemical activities of organic ethno-biofertilizer formulations for maize growth enhancement

Abstract

Organic ethno-biofertilizer (OEB) is a low-cost, eco-friendly agricultural input derived from locally available materials, aligning with sustainable and smallholder farming practices. By combining agricultural residues with beneficial microorganisms, OEB offers an environmentally responsible alternative to restore soil health and improve crop productivity. This study aimed to assess and characterize OEB formulations based on local wisdom, evaluate their biochemical activities, and determine the effectiveness of plant growth-promoting bacteria (PGPB) in enhancing maize growth through bioassays. Six OEB formulations were tested, from which 12 PGPB isolates were obtained and evaluated to identify superior strains. A randomized block design (RBD) with 13 treatments (one control and 12 bacterial isolates) and three replications was employed. The highest bacterial and nitrogen-fixing contents were observed in the OEB formula combining plant-based (bamboo root) and animal-based (rabbit urine) components. Bioassay results showed that all 12 isolates significantly enhanced maize growth and phytohormone production. Based on performance rankings, two superior isolates (GPNF9 and GPNF12) were identified, which significantly increased plant height, root length, and fresh weight compared to the control. Biochemical analyses revealed that GPNF9 and GPNF12 produced indole acetic acid (IAA) at 1.153 and 1.394 ppm, and nitrogenase activity at 0.560 and 1.381 µM mL⁻¹ g⁻¹ h⁻¹, respectively. Molecular identification classified GPNF9 as Stenotrophomonas sp. HH10 and GPNF12 as Enterobacter sp. strain YF3. These findings suggest that integrating plant-and animal-based OEB with selected PGPB isolates can effectively support sustainable maize production.