Phosphorus accumulation characteristics in Polygonum hydropiper and rhizosphere properties affected by poultry manure application

Land-applied poultry manure threatens to water environments, particularly because of its high concentration of phosphorus (P). Polygonum hydropiper is efficient in extracting soil excess P, thereby reducing the risk of P runoff and leaching. Rather, little is understood about the effects of poultry manure on soil properties and the P-accumulating characteristics of this plant species. Two pot experiments were conducted to investigate P accumulation and rhizosphere properties in a mining ecotype (ME) of P. hydropiper from Shifang phosphate-mining area and the contrasting non-mining ecotype (NME), with the first experiment at different poultry manure application rates (0, 25, 50, 75, 100 g kg⁻¹ dry soil) and the second experiment under the optimum poultry manure concentration (75 g kg⁻¹) over three growth periods. The ME's shoot biomass and P accumulation increased with poultry manure application rates up to 75 g kg⁻¹ and increased with increasing growth periods. Shoot biomass and P accumulation of the ME were significantly greater than those of the NME at 75 g kg⁻¹ in both experiments. At the optimum poultry manure rate (75 g kg⁻¹), H₂O-Pi (Pi, inorganic P), H₂O–, NaHCO₃− and NaOH-Po (Po, organic P) were more depleted in ME rhizosphere than NME rhizosphere whereas NaHCO₃− and NaOH-Pi increased more in ME rhizosphere than NME rhizosphere, irrespective of growth periods. Soil acid and alkaline phosphatases, phosphodiesterase and phytase activities of the ME significantly increased with manure rates up to 75 g kg⁻¹. Higher enzymatic activities were observed in poultry manure soil than the control and in the rhizospheric soil than bulk soil. The ME showed significantly greater activities of rhizospheric acid phosphatase and phytase than the NME in poultry manure soil at 8 weeks, when its P accumulation showed the largest increase. Therefore, the ME can extract much greater P than the NME from poultry manure-amended soil, probably through the changes in its rhizosphere properties.