Background: The dynamics of phosphorus (P) in the environment is important for regulating nutrient cycles in natural and managed ecosystems and an integral part in assessing biological resilience against environmental change. Organic P (Po) compounds play key roles in biological and ecosystems function in the terrestrial environment being critical to cell function, growth and reproduction. Scope: We asked a group of experts to consider the global issues associated with Po in the terrestrial environment, methodological strengths and weaknesses, benefits to be gained from understanding the Po cycle, and to set priorities for Po research. Conclusions: We identified seven key opportunities for Po research including: the need for integrated, quality controlled and functionally based methodologies; assessment of stoichiometry with other elements in organic matter; understanding the dynamics of Po in natural and managed systems; the role of microorganisms in controlling Po cycles; the implications of nanoparticles in the environment and the need for better modelling and communication of the research. Each priority is discussed and a statement of intent for the Po research community is made that highlights there are key contributions to be made toward understanding biogeochemical cycles, dynamics and function of natural ecosystems and the management of agricultural systems

) MacMillan] has potential as a pasture and grain legume in the Midwestern USA, but has proven to be somewhat problematic in inoculation response. We identified inoculant-quality Rhizobium strains from among 120 isolates trapped from 12 sites within the native range of Illinois bundleflower, then determined the effect of inoculation with four selected strains on plant dry matter and plant total N in growth chamber, greenhouse, and field experiments. We also studied nodule occupancy in the field. In field experiments at Salina (Kansas) and Becker (Minnesota) inoculated plants yielded 170% greater dry matter and total N on average than did uninoculated and N fertilized controls at each site in the seeding year. There were no differences in plant response among the Rhizobium strains used, uninoculated plants were devoid of nodules, and the response to inoculation was similar for the three plant accessions considered. In the second growing season, plant regrowth was different at Salina and Becker. At Salina, all plant accessions regrew and no differences were found between inoculated and control treatments in the second year. At Becker, toward the northern extreme of the range for Illinois bundleflower, only a MN ecotype regenerated in the second year, and inoculation was a requirement for plant persistence. Regrowth was similar with each of the four inoculant strains used. While 90% of the rhizobia recovered from nodules in the seeding year at Becker had genetic fingerprints similar to the inoculant strains, in the second year this percentage had declined to 70%. Our results highlight the importance of Rhizobium strain selection if the use of native legumes is to be increased.

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Soil microbial communities play critical roles in maintaining natural ecosystems such as the Campos biome grasslands of southern South America. These grasslands are characterized by a high diversity of soils, low available phosphorus (P) and limited water holding capacity. This work aimed to describe prokaryotic communities associated with different soil types and to examine the relationship among these soil communities, the parent material and the soil nutrient status. Five Uruguayan soils with different parent material and nutrient status, under natural grasslands, were compared. The structure and diversity of prokaryotic communities were characterized by sequencing 16S rRNA gene amplicons. Proteobacteria, Actinobacteria, Firmicutes, Verrucomicrobia, Acidobacteria, Planctomycetes, and Chloroflexi were the predominant phyla. Ordination based on several distance measures was able to discriminate clearly between communities associated with different soil types. Edge-PCA phylogeny-sensitive ordination and differential relative abundance analyses identified Archaea and the bacterial phyla Firmicutes, Acidobacteria, Actinobacteria and Verrucomicrobia as those with significant differences among soil types. Canonical analysis of principal coordinates identified porosity, clay content, available P, soil organic carbon and water holding capacity as the main variables contributing to determine the characteristic prokaryotic communities of each soil type.

Illinois bundleflower (Desmanthus illinoensis (Michx.) Macmillan) has potential as a grain and forage legume for the American Midwest. Inoculant-quality rhizobia for this legume have been identified but not previously characterized. Rhizobia trapped from 20 soils in the natural range of the Illinois bundleflower had characteristics that placed them overwhelmingly within the species Rhizobium giardinii, one of the few occasions this species has been recovered from legumes, raising questions on the biogeography and spread of midwestern prairie rhizobia.