| In recent years,the production of manure increased rapidly.Manure has generally been discharged directly into the environment and applied to soils with an inappropriate way,which resulting the phosphorus(P)accumulation in soils.Excess P in soils raises water eutrophication process due to its surface runoff or leaching.Phytoextraction,using P accumulators to extract P from P-enriched soils,has been suggested as an effective strategy to reduce the risk of P loss.Experiments were carried out to investigate the effect of manure on P accumulation characteristics and P removal potential in a mining ecotype(ME)of P.hydropiper screened as P accumulator earlier,with a non-mining ecotype(NME)as contrast.The following is a summary of the primary results:1.Shoot biomass,P concentration and P accumulation of two ecotypes under manure amended soila were higher than those of the control.Maximum shoot biomass and shoot P accumulation of the ME were noticed in soils amended with 75 g kg-1 poultry manure,100 g kg-1 swine manure and 100 g kg-1 dairy manure.A 1.09-and 2.62-fold shoot biomass and P accumulation was observed in the ME compared to the NME,respectively.P concentration of two ecotypes reached a peak value when soils was amended with 100 g kg-1 manure,and P concentration of the ME was 6.74%and 46.76%higher than the NME.Bioaccumulation coefficient of two ecotypes decreased apparently with the increasing manure application rate.Transfer coefficient was higher than 1.Compared with control,acid phosphatase and phytase activities of P.hydropiper grown in manure impacted soils increased by 20.72%-160.78%and 9.79%-145.40%,respectively.Furthermore,acid phosphatase and phytase activities of the ME reached its peak value in soils amended with 75 g kg-1 poultry manure,100 g kg-1 swine manure and 100 g kg-1 dairy manure,reapectively,and significantly higher rhan the NME.3.The biomass and P accumulation of two ecotypes was higher than those of the control,irrespective of growth periods and manure treatments.Moreover,the ME grown in soils amended with 75 g kg-1 poultry manure,100 g kg-1 swine manure and 100 g kg-1 dairy manure were 1.23-1.70 and 1.33-1.79 times higher than those of the NME,respectively.Maximum biomass and P accumulation of two ecotypes of P.hydropiper were observed at 12 weeks with the increasing growth periods.Periodic P accumulation of P.hydropiper at 6-8 weeks accounted for more than 66.58%of total P accumulation in poultry manure treatments and swine manure treatments,while maximum periodic P accumulation was observed at 0-6 weeks in dairy manure treatments.The ME showed higher periodic P accumulation than the NME before 8 weeks.Maximum P accumulation rate of the ME was observed at 8 weeks,irrespective of manure treatments,which was 1.38-1.74 times higher than that of the NME.At 12 weeks,P extraction rate and P removed of two ecotypes reached a peak value,while plant effective number(PEN)was lowest.In addition,the ME demonstrated higher P extraction rate and P removed than the NME,while PEN was lower than the NME,indicating that the ME could remove more P from soils at suitable manure treatments.2.Activities of acid phosphatase(ACP),alkaline phosphatase(ALP),phosphodiesterase(PDE)and phytase in the rhizosphere and bulk soils of two ecotypes amended with 75 g kg-1 poultry manure,100 g kg-1 swine manure and 100 g kg-1 dairy manure increased significantly compared to the control.Higher ACP,ALP and PDE activities in the rhizosphere and bulk soils of two ecotypes was observed at poultry manure treatments,dairy manure treatments and dairy manure treatments,respectively.Phytase activities in the rhizosphere and bulk soils of two ecotypes at swine manure treatments was 304.48%and 839.59%higher than those at poultry manure and dairy manure treatments.Activities of ACP,ALP,PDE and phytase were higher in the rhizosphere than in bulk soils at suitable manure concentration.With the increasing growth periods,ACP and PDE activities in the rhizosphere soils had no changes,but ALP acti,vities increased up to 8 weeks,beyond which a stable trend was observed.Phytase activities in the rhizosphere soils decreased significantly with the increasing growth periods.Phytase activities of the ME in the rhizosphere soils were 1.15 and 1.48 times higher than those of the NME before 8 weeks.The concentration of P fractions in manure amended soils were greater than those in the control.In addition,NaHCO3-P and HCl-P concentration at swine manure treatments were higher than those at poultry manure and dairy manure treatments.Rhizosphere H2O-Pi and H2O-Po concentration of both ecotypes were higher than bulk soils.Increases in rhizosphere NaHCO3-Pi and NaOH-Pi concentration of P.hydropiper was observed,and the concentration of NaHCO3-Pi and NaOH-Pi of the ME in the rhizosphere soils were significantly higher than the NME.However,depleted in rhizosphere NaHCO3-Po and NaOH-Po of P.hydropiper was observed,and the concentration of NaHCO3-Po and NaOH-Po of the ME in the rhizosphere soils were significantly lower than the NME.With the increasing growth periods,the concentration of H2O-Pi,H2O-PO and NaHCO3-Pi of the ME in the rhizosphere soils decreased drastically at 8 weeks,and the decreased range were higher than the NME.4.Dry weight of the ME ranged from17.44 to 25.75 Mg ha-1.Shoot P content ranged from 3.97 to 4.75 g kg-1.P removal ranged from 68.54 to 119.07 kg P ha-1.Maximum of PEN of ME was observed in dairy manure impacted soils,and the number was 7.Minimum of PEN of ME was observed in poultry manure impacted soils,and the number was 4.P extraction rate of the ME grown in poultry manure impacted soils was 4.19%,and P extraction rate of the ME grown in swine manure impacted soils was lowest.After planting the ME of P,hydropiper,the concentration of water extractable P and available P in manure impacted soils decreased by 2.89%-46.30%and 3.04%-16.42%,respectively.These results demonstrated that the ME could remove more P from the manure impacted soils and reduce the risk of excessive P loss to the surface water. |
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