- Agronomic: grass (misc. perennial), peanuts
- Crop Production: nutrient cycling, nutrient management
Rhizoma peanut (RP) [Arachis glabrata Benth.] is incorporated into grassland pastures, such as bahiagrass (BG) [Paspalum notatum Flüggé], to increase pasture feed quality and reduce the need for nitrogen (N) fertilizer inputs. Apart from N, phosphorus (P) is important for forage and animal nutrition. The nutrient dynamics of P is of interest because of its role in the contamination of water bodies. Soil P is influenced by management practices and crops and soil types. Applying P fertilizers to soils with high P sorption capacity, such as the Southern Coastal Plains, Ultisols, can render a large percent of the applied P inaccessible for plant uptake. Although forage species differ in their ability to solubilize soil P for uptake, there is also indication that bulk soil and rhizosphere-associated microorganisms differ across plant species, in terms of their impact on plant-available soil P. Soil microorganisms modify soil P sorption equilibria and increase inorganic P in soil solution through release of organic compounds and enzymes that solubilize P from soil minerals, while organic P is released through biological mineralization. Through P isotope labelling techniques, molecular and metatranscriptomic approaches, and microscopic imaging, this study aims to identify the impact soil microbial communities have for enhancing P availability in BG-RP mixed pastures compared to BG monoculture pastures. Locating and identifying specific microbial groups associated with soil P availability in pastures with and without a legume component, provides a means for evaluating the potential to enhance fertilizer P use efficiency through legume inclusion and related microbial functions.
Project objectives from proposal:
- The integration of RP into BG system will enhance the community and functionality of both BG and RP associated microbial groups that are responsible for P solubilization and mineralization in microbial-soil interface and P exchange in plant-microbial interface.
- The enhancement of microbial mediated P cycling in hypothesis 1 will be controlled by a set of P cycling genes (Table 1), including but not limited to the genes responsible for solubilizing inorganic P (e.g., gcd and PqqABCDEF), the genes responsible for mineralizing P (e.g. PhoADN, aphA, olpA, php, glp, and app, and the genes involved in microbial-P exchange and plant uptake at the microbial-root P interface.
- Soil microbial P cycling processes (genes and enzymes release), especially the genes involved in P uptake and transport as well as P starvation genes, will be suppressed when P mineral fertilizers are applied.
- Determine the distribution of applied 33P-labelled mineral P fertilizer on soil P pools, plant P uptake and P transfer under BG monoculture versus a BG-RP mixture.
- Identify microbial communities in the different belowground plant parts of bahiagrass (root+rhizome), rhizoma peanut (roots+ rhizome+ nodules), and in the rhizosphere, in response to forage species composition with or without mineral P fertilizer.
- Use qPCR to quantify organic P mineralization (e.g., phoC and bpp) and inorganic P dissolution (e.g., pqqC) genes in rhizosphere soil and bulk soil across forage species with and without P fertilizer.
- Profile genome expression of root microbiomes (including AMF) and root cells, with emphasis on identifying and quantifying the expression of key genes that are involved in P uptake and transport, as well as P-exchange (and P-metabolism) in the different forage systems (monoculture vs mixture) with or without mineral P fertilizer.
- Organize in-person visits with producers in North, Central, and South Florida and present our project findings to them.