Effects Of Three Aquatic Plants On Soil Properties And Depletion Of Rhizosphorus Nitrogen And Phosphorus

In recent years, due to massive population, rapid development of economy, and unreasonable utilization of natural resources, agricultural nonpoint pollution becomes more and more serious. Study proves that plant buffer strips has an important effect on removing agricultural nonpoint pollutants (nitrogen, phosphorus). The consumption of nitrogen and phosphorus of plant growth in buffer strips is one of the main mechanisms to remove agricultural nonpoint pollutants. Through affecting the soil structure (soil water repellency index and soil aggregate stability) and transforming the soil microorganism community, the consumption of soil nitrogen and phosphorus of different plants will be altered; especially there will be significant variance of nitrogen and phosphorus in rhizosphere soil. We plant Lythrum salicaria, Iris pseudacorus and Acorus calamus in greenhouse. Research contents included:(1) changes of soil water repellency index and aggregate stability, (2) changes of rhizosphorus soil microbial biomass, (3) nitrogen and phosphorus accumulation in aquatic plants, (4) changes of rhizosphorus soil nitrogen and phosphorus, (5) the depletion of rhizosphorus soil nitrogen and phosphorus of different aquatic plants with the interaction of soil, plants and microorganism.The composition of soil aggregate of different plants was different. The>0.25 mm soil aggregate was dominant component (76.4-87%), and macro-aggregate increased with time passing. Soil aggregate stability of 5-10 mm and 2-5 mm were Iris pseudacorus> Lythrum salicaria>Acorus calamus. Soil aggregate stability of 2-5 mm was higher than 5-10 mm. Soil water repellency index was Lythrum salicaria>Iris pseudacorus>Acorus calamus.Rhizosphorus soil microbial biomass carbon and nitrogen were increasing constantly with time passing, and became stable 70 days later. Rhizosphere soil microbial biomass carbon and nitrogen were Lythrum salicaria> Iris pseudacorus> Acorus calamus.the phospholipid fatty acid (PLFA) contents of three rhizosphere soils were Lythrum salicaria> Iris pseudacorus>Acorus calamus. There were significant differences (p<0.05) among Lythrum salicaria,Iris pseudacorus and Acorus calamus in PLFA contents of rhizosphere soils. Relativity analysis showed that rhizosphere soil microbial biomass had positive correlation with soil aggregate stability and soil water repellency index.The accumulation of nitrogen and phosphorus increased continuously with the aquatic plants growth. The maximum accumulation of nitrogen was 205.65 mg/plant (Lythrum salicaria),168.01 mg/plant(Iris pseudacorus), and 46.91 mg/plant (Acorus calamus) in aboveground parts. The maximum accumulation of phosphorus was 37.66 mg/plant (Lythrum salicaria),28.50 mg/plant (Iris pseudacorus), and 10.28 mg/plant (Acorus calamus) in aboveground parts. The maximum accumulation of nitrogen was 87.81 mg/plant (Acorus calamus),87.62 mg/plant (Lythrum salicaria), and 78.48 mg/plant (Iris pseudacorus) in underground parts. The maximum accumulation of phosphorus was 26.39 mg/plant (Acorus calamus),24.05 mg/plant (Lythrum salicaria), and 22.64 mg/plant (Iris pseudacorus) in underground parts. Nitrogen and phosphorus of Lythrum salicaria and Iris pseudacorus mainly accumulated in aboveground parts. Nitrogen and phosphorus of Acorus calamus mainly accumulated in underground parts. Nitrogen and phosphorus accumulations of different plants had significantly positive correlation with biomass of plants.The contents of three rhizosphere soils total nitrogen,total phosphorus and available phosphorus showed downtrend. The content of three rhizosphere soils available nitrogen reduced first then increased. The depletion rate of three rhizosphere soils total nitrogen and total phosphorus were Lythrum salicaria>Iris pseudacorus>Acorus calamus. Acorus calamus had significant differences (p<0.05) comparing with Lythrum salicaria and Iris pseudacorus, while there were no significant differences (p<0.05)between Lythrum salicaria and Iris pseudacorus in the depletion of rhizosphere soils total nitrogen. There were no significant differences (p<0.05) among Lythrum salicaria, Iris pseudacorus and Acorus calamus in the depletion of rhizosphere soils phosphorus.