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
Aims Intercropping can improve plant yields and soil phosphorus (P) use efficiency. This study compares inter-and intra-species intercropping, and determines whether P uptake and shoot biomass accumulation in intercrops are affected by soil P availability. Methods Four barley cultivars (Hordeum vulgare L.) and three legume species (Trifolium subterreneum, Ornithopus sativus and Medicago truncatula) were selected on the basis of their contrasting root exudation and morphological responses to P deficiency. Monocultures and barley-barley and barley-legume intercrops were grown for 6 weeks in a pot trial at very limiting, slightly limiting and excess available soil P. Aboveground biomass and shoot P were measured. Results Barley-legume intercrops had 10-70% greater P accumulation and 0-40% greater biomass than monocultures, with the greatest gains occurring at or below the sub-critical P requirement for barley. No benefit of barley-barley intercropping was observed. The plant combination had no significant effect on biomass and P uptake observed in intercropped treatments.Conclusions Barley-legume intercropping shows promise for sustainable production systems, especially at low soil P. Gains in biomass and P uptake come from inter-rather than intra-species intercropping, indicating that plant diversity resulted in decreased competition between plants for P.
, Response-based selection of barley cultivars and legume species for complementarity: Root morphology and exudation in relation to nutrient source, Plant Science http://dx.doi.org/10. 1016/j.plantsci.2016.11.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1 Title 1Response-based selection of barley cultivars and legume species for complementarity: Root 2 morphology and exudation in relation to nutrient source 3 Author names 4Courtney D. Giles to assess the influence of P supply and N source on the phenotypic plasticity of nutrient foraging traits 28 in barley (H. vulgare L.) and legume species. Root morphology and exudation were determined in six 29 plant nutrient treatments. A clear divergence in the response of barley and legumes to the nutrient 30 treatments was observed. Root morphology varied most among legumes, whereas exudate citrate and 31 phytase activity were most variable in barley. Changes in root morphology were minimized in plants 32provided with ammonium in comparison to nitrate but increased under P deficiency. Exudate phytase 33 activity and pH varied with legume species, whereas citrate efflux, specific root length, and root 34 diameter lengths were more variable among barley cultivars. Three legume species and four barley 35 cultivars were identified as the most responsive to P deficiency and the most contrasting of the 36 cultivars and species tested. Phenotypic response to nutrient availability may be a promising approach 37 for the selection of plant combinations for minimal input cropping systems. 38 no P; P1, 0.5 mM P; P2, 1.0 mM P; SRL, specific root length. 47
Citrate and phytase root exudates contribute to improved phosphorus (P) acquisition efficiency in Nicotiana tabacum (tobacco) when both exudates are produced in a P deficient soil. To test the importance of root intermingling in the interaction of citrate and phytase exudates, Nicotiana tabacum plant-lines with constitutive expression of heterologous citrate (Cit) or fungal phytase (Phy) exudation traits were grown under two root treatments (roots separated or intermingled) and in two soils with contrasting soil P availability. Complementarity of plant mixtures varying in citrate efflux rate and mobility of the expressed phytase in soil was determined based on plant biomass and P accumulation. Soil P composition was evaluated using solution P NMR spectroscopy. In the soil with limited available P, positive complementarity occurred in Cit+Phy mixtures with roots intermingled. Root separation eliminated positive interactions in mixtures expressing the less mobile phytase (Aspergillus niger PhyA) whereas positive complementarity persisted in mixtures that expressed the more mobile phytase (Peniophora lycii PhyA). Soils from Cit+Phy mixtures contained less inorganic P and more organic P compared to monocultures. Exudate-specific strategies for the acquisition of soil P were most effective in P-limited soil and depended on citrate efflux rate and the relative mobility of the expressed phytase in soil. Plant growth and soil P utilization in plant systems with complementary exudation strategies are expected to be greatest where exudates persist in soil and are expressed synchronously in space and time.
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