Flood Stress and Growth Management For Plants in Arable Soils Using Cocopeat-Plant Growth Promoting Rhizobacteria Formulation

This research formulated and evaluated the efficiency of a biofertilizer, cocopeat encapsulated plant growth-promoting rhizobacteria (cocopeat-PGPR), in the management of flood stress and the growth of Zea mays (maize) seeds cultivated under flood conditions. Rhizobacteria were isolated from a weed (Phyllanthus amarus) and screened for plant growth-promoting (PGP) traits; Indole-3-acetic acid (IAA) production and phosphate solubilization. Rhizobacteria were further tested for PGP activity using a seed germination bioassay, and those with superior performance were used for formulation and a pot experiment. Formulations were prepared by homogenizing 20ml of each PGPR standardized inoculum with 2g of oven-dried cocopeat and 24 g of starch gel, pelleted, and dried at room temperature. The efficiency of the formulations was evaluated in a pot experiment by measuring plant height (PH), shoot length (SL), and root length (RL) of the treated maize seeds weekly. Two sets of treatments were performed: seeding with one cocopeat-PGPR pellet/pot and four cocopeat-PGPR pellets/pot. Controls were without the cocopeat-PGPR formulation. Flood conditions were simulated by waterlogging the treatments without drainage. Five rhizobacterial isolates were obtained; two tested positive for phosphate solubilization (CE and C), and two tested positive for IAA production (CE and PP). These isolates also demonstrated superior growth performance during the seed germination bioassay. At day 7 of the pot experiment, no growth was recorded for maize seeds treated with a single cocopeat-PGPR pellet or for the control. However, at day 7, in treatments with four cocopeat-PGPR pellets, only cocopeat-CE supported maize seed growth and sustained growth. The mean SL, RL, and PH recorded for the seeds were 2.4 cm, 3.1 cm, and 15.7 cm, respectively. Before day 14, the maize seeds withered. The PGPR (CE) was identified by 16S rDNA sequencing as Priestia flexa. This study, therefore, examines the potential of cocopeat (Priestia flexa) to mitigate flood stress and promote growth in maize plants.