Phytoextraction efficiency of P by mining ecotype of Polygonum hydropiper grown in soils amended with swine manure

Objectives Excess phosphorus (P) in soil is concerned for easy loss into environment. The phytoextraction efficiency of P by mining ecotypic Polygonum hydropiper (ME), a P enriching plant, was investigated for the effective remediation of excess P from soils and reduced risk of P loss.

Methods A field plot experiment was conducted with 4 swine manure application rates of 0 (CK), 1, 2, 3 kg/m² with 3 replicates based on the safety rate of P fertilization in farmland (< 200 kg/hm²). The shoots of the ME were harvested after 3 months of transplanting and digested with a microwave digestion system (CEM MARS5, USA). The P contents in plant samples were determined by an auto discrete analyzer (AQ2, UK). Soil samples in the 0–20 cm and 20–40 cm layers before transplanting and after harvest were obtained using the five-point sampling method. The concentrations of water-soluble P and available P in soils were measured.

Results The shoot biomasses of ME with different dosages of swine manure treatments were significantly greater than that of CK, with the increase of 18.4, 24.6 and 42.0 g/plant. The shoot biomass of ME in treatment of 3 kg/m² swine manure was 2.16 times greater than that of CK. P concentrations in the shoots of ME applied with different dosages of swine manure were significantly greater than that of CK, with the increase of 0.60, 0.91 and 1.49 g/kg respectively. The P content in shoot of ME in treatment of 3 kg/m² swine manure was 1.53 times greater than that of CK. Compared with CK, P accumulations in shoots of ME significantly increased with increasing application rate of swine manure, with the increments of P 84.0, 124 and 236 mg/plant respectively for the three manure dosage treatments. The P accumulation in shoots of ME under treatment of 3 kg/m² swine manure was 3.32 times greater than that of CK. The concentrations of water-soluble P and available P in the 0–20 cm soil layer after harvest decreased by 74.9%–81.5% and 48.9–60.0% respectively, compared with those before transplanting. However, no significant changes were observed for the concentrations of water-soluble P and available P in the 20–40 cm soil layer.

Conclusions Mine ecotype of Polygonum hydropiper was proved to be an efficient plant for phytoextraction of P brought into soils by swine manure application. The significant decrease of water soluble and available P in surface soils reduce the possible P loss into environment.