Indigenous arbuscular mycorrhizal fungi play a role in phosphorus depletion in organic manure amended high fertility soil

The species richness and propagule number of arbuscular mycorrhizal fungi(AMF)are high in intensively-managed agricultural soils.Past research has shown that AMF improve crop phosphorus(P)uptake under low soil P conditions,however it is unclear if AMF play a role in high Olsen-P soils.In this study,we investigated whether native fungal benefits exist under high P input field conditions in-situ and contribute to P utilization.We installed in-grow tubes which were sealed with different membrane pore sizes(30 or 0.45μm)to allow or prevent AMF hyphae access to the hyphal compartment and prevent cotton roots from penetrating the chamber.We used the depletion of soil available P(Olsen-P)in the hyphae accessed compartment to indicate P uptake by the native AMF community.Our results showed that the native AMF mediated P depletion and microbial biomass P(MBP)turnover and caused the largest Olsen-P depletion ratio and MBP turnover ratio in the high P treatments(Olsen-P:78.29 mg kg^(-1)).The cotton roots in each fertilization regime were colonized by a unique AMF community and Glomus and Paraglomus were the dominant genera,implying the longterm fertilization regimes domesticated the AMF community.We conclude that native AMF caused the P depletion and P turnover even under high soil Olsen-P conditions.

Rhizosphere effect of different aquatic plants on phosphorus depletion

A series of pot experiments with Alternanthera philoxeroides,Typha latifolia,Sagittaria sagittifolia and Phragmites communis were conducted to assess the phosphorus depletion effect in the rhizosphere.The ratio of root to shoot,root morphology,phosphorus uptake efficiency and phosphorus utilization efficiency were analyzed.An obvious variation in phosphorus concentrations between the rhizosphere soil and non-rhizosphere soil was observed.The water-soluble P contents in the rhizosphere soil of A.philoxeroides,T.latifolia,S.sagittifolia and P.communis were reduced by 81%,42%,18%and 16%,respectively,compared with that in the non-rhizosphere soil.A.philoxeroides had the highest phosphorus uptake efficiency(1.32 mg/m),while T.latifolia achieved the effective phosphorus depletion by the strong rooting system and the high phosphorus uptake efficiency(0.52 mg/m).T.latifolia not only used phosphorus to produce biomass economically,but also adjusted carbon allocation to the roots to explore the soil for more available phosphorus.A.philoxeroides and T.latifolia were more effective in depleting phosphorus in the rhizosphere than S.sagittifolia and P.communis.