Field Assessment of a Plant Growth-Promoting Pseudomonas on Phytometric, Nutrient, and Yield Components of Maize in a Milpa Agrosystem

The traditional milpa system, a polyculture originating in Mesoamerica, centers around maize (Zea mays L.), associated with pumpkin (Cucurbita sp.) and beans (Phaseolus vulgaris L.). The application of plant growth-promoting rhizobacteria (PGPR) under a milpa agrosystem has been little explored. In this study, a maize crop in a milpa system was fertilized with the PGPR Pseudomonas fluorescens UM270 during the 2021 and 2023 seasons, and various phytoparameters (plant height, root length, chlorophyll concentration, root dry weight and total plant dry weight), total production, and grain nutrition were evaluated. The results showed that UM270 improved chlorophyll concentration and increased plant height, root length, and dry weight in maize plants. Co-fertilization with UM270 and diammonium phosphate (DAP) significantly improved plant and corn cob weight compared to controls with single fertilizations in both the 2021 and 2023 seasons. Notably, corn production increased by more than 40% in the corn monoculture inoculated with UM270 compared to the uninoculated plants. The UM270 + DAP cofertilization in the monoculture was also increased by more than 50% in both cycles. When analyzing the nutritional content of the corn cob, nitrogen and phosphorus increased with the inoculation with UM270, while other elements, such as potassium and calcium, were higher in treatments co-inoculated with UM270 + DAP. Based on our research, this study is the first to report the milpa as a suitable model for bioinoculation with PGPR, demonstrating its potential to increase maize yield and benefit other associated crops.