Abstract
Many soils including urban soils have high legacy soil phosphorus (P) due to repeated applications of P fertilizers, but a large portion legacy soil P is fixed by calcium in the calcareous soils. Phosphorus solubilizing bacteria (PSB) have the ability to transfer fixed (non-labile) soil P into bioavailable P. The aim of this study was to isolate P solubilizing bacteria from the rhizospheres of four local native plants [broomsedge bluestem (Andropogon virginicus), giant sword ferns (Nephrolepis biserrata), sawgrass (Cladium jamaicense), and sea ox-eye daisy (Borrichia frutescens)] grown in low bioavailable P calcareous soils and to determine their ability to solubilize P. A total of 44 strains of PSB were isolated with 15 of them being identified by sequencing the 16S rRNA genes as Bacillus flexus, Beijerinckia fluminensis, Enterobacter ludwigii, Enterobacter sp., and Pantoea cypripedii. After a 7-day incubation, these strains reduced pH to <4.27 and increased water-soluble P up to 588 mg L−1. Enterobacter ludwigii showed superior P solubilizing ability amount PSB isolated. Therefore, the isolated strains from the local native environment have the potential to thrive in local calcareous soils and possess strong ability to transform non-labile P into bioavailable forms for plants to uptake.
Highlights
Global food security depends on the availability of phosphorus (P) because it is a nonrenewable mineral resource and an essential nutrient for plants
Phosphorus solubilizing bacteria (PSB) existed in all four low P soils and indicated that PSB play an important role in providing P to these native plants
This research highlights the connection between local native plants and PSB suggesting that native plants play an important role in establishing and maintaining thriving PSB communities
Summary
Global food security depends on the availability of phosphorus (P) because it is a nonrenewable mineral resource and an essential nutrient for plants. Phosphorus along with nitrogen (N) and potassium (K) are primary nutrients, known as a macronutrients which are required in the largest amounts by plants. Phosphorus is essential for plant reproduction and is required for critical plant functions (e.g., nutrient transport, photosynthesis, respiration). In order to maintain high productivity of crops, inorganic and organic P fertilizers are applied at rates as high as 300 kg P2O5 ha−1 for commercial crops and even higher rates for residential landscape plants. The P use efficiency of crops from fertilizer application is estimated to be as low as 16% and crops grown in calcareous soils may have an even lower rate because applied P can be precipitated rapidly by calcium in calcareous soils (Dhillon et al, 2017). A majority of P applied as fertilizers is retained in soils and a small fraction of soil P enters groundwater by leaching, or surface water by runoff, which cause eutrophication of nearby
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