施氮提高矿山生态型水蓼富集土壤磷能力研究

【目的】适宜施氮可促进植物对磷的积累。本文探讨了施氮对磷富集植物磷积累能力的促进作用，为有效利用植物修复土壤磷过剩、减少磷的面源污染提供依据。【方法】以磷富集植物矿山生态型水蓼（Polygonum hydropiper）为研究对象，非矿山生态型水蓼为对照，进行了土培盆栽试验。供试土壤为灰潮土，每盆（6 L）装土6 kg，基施800 mg/kg磷，陈化4周后分别施入处理的施氮量（0、25、50、100、200 mg/kg土），陈化后土壤有效磷为457 mg/kg。取2.5 kg土装入直径15 cm、高7.5 cm的尼龙纱网根袋（400目，孔径约38 μm）中，置于盆中央，其余3.5 kg土装入盆中。选取三叶一心的水蓼幼苗移栽至根袋中，每盆种2株，按田间持水量的70%确定灌水量，移栽10周后收获，调查水蓼生物量、分析植株磷含量。去掉表层2 cm土壤，采集根袋内、外土壤作根际、非根际土，用于测定土壤有效磷含量。【结果】1) 供试施氮量范围内，矿山生态型水蓼地上部生物量、磷含量、磷积累量均在100 mg/kg土施氮量下达到最大，为不施氮处理的4.57、1.33、6.10倍，地上部磷积累量为228 mg/株；矿山生态型地上部磷含量和磷积累量在50、100、200 mg/kg土施氮量下均显著高于非矿山生态型，分别为非矿山生态型的1.14、1.08、1.03倍和1.25、1.11、1.09倍。2) 随施氮量的增加，矿山生态型地下部生物量、磷含量、磷积累量均逐渐增加，但均低于非矿山生态型，地下部磷积累量仅为非矿山生态型的39.5%～84.2%。3) 施氮处理条件下，矿山生态型磷富集系数及转运系数均大于1，在100 mg/kg土施氮量下达最大值，分别为12.5和1.33，明显高于相同施氮处理下非矿山生态型，为非矿山生态型的1.09、1.53倍，这表明矿山型水蓼向上运转磷的能力更强。4) 施氮增加了矿山生态型水蓼根际土壤有效磷含量，在施氮量为50、100、200 mg/kg土 时增长最为明显，且明显高于非根际土壤，更有利于植株对磷的吸收积累。【结论】高磷条件下，施氮提高了根际土壤中的有效磷含量，增加了矿山生态型水蓼地上部积累磷的能力，100 mg/kg土施氮量为盆栽试验适宜用量，实际应用中的用量还需进一步试验。

Application of nitrogen to increase phosphorus accumulation of Polygonum hydropiper with mining ecotype

【Objectives】Appropriate nitrogen (N) application can improve phosphorus (P) accumulation in plants. The effect were testified using phosphorous hyper accumulator plants in this paper, which would provide practical support for effective remediation in environmental P pollution and the non-point source pollution of P.【Methods】Taking mining ecotype (ME) of Polygonum hydropiper as tested materials and non-mining ecotype (NME) as control, a pot experiment was conducted in a greenhouse under natural light at Sichuan Agricultural University, Sichuan Province, China in 2015. The used soil, calcareous alluvial soil, was applied 800 mg/kg of P and then designed N levels (0, 25, 50, 100 and 200 mg/kg soil) after standing for 4 weeks for stabilizing. The soil available P concentration became 425 mg/kg afterwards. Total 6 kg of the treated soils, 2.5 kg was loaded inside the root bags with 38 μm of pores in the central of pots and 3.5 kg outside the bags. 2 plants at age of three leaves and one sprout were transplanted inside the root bags for each pot, and the soil moisture was kept 75% of the field capacity. After growing for 10 weeks, the plants were harvested, the biomass were weighed and the P concentrations were determined. The soil samples both inside and outside the root bags were raped off the top 2 cm surface, and the available P concentrations were analyzed separately.【Results】1) The biomass, P concentration and P accumulation in shoots of ME reached the maximum under the N application rate of 100 mg/kg, which were 4.57, 1.33 and 6.10 times of those in the control plants. The P accumulation in shoots was increased to 228 mg/plant. The P concentration and P accumulation in shoots of ME were significantly higher than those in NME under N application rate of 50, 100 and 200 mg/kg, respectively, which were 1.14, 1.08, 1.03 and 1.25, 1.11, 1.09 times of NME. 2) The biomass, P concentration and P accumulation in roots of ME were increased with increasing N application. ME presented lower P concentration and P accumulation in roots, the P accumulation in roots were only 39.5% - 84.2% of NME. 3) Under the condition of N application, both bioaccumulation coefficient and translocation factor of P in ME were larger than 1, and reached the maximum under 100 mg/kg N application, which were 12.5 and 1.33, respectively. The bioaccumulation coefficient and translocation factor of P in ME were significantly higher than those in NME, which were 1.08 and 1.53 times of NME under 100 mg/kg N application, respectively. This indicated that the higher P transportation from roots to shoots in ME than the NME. 4) The N application improved P availability in rhizosphere soils of ME, which was more pronounced at 50, 100 and 200 mg/kg. In addition, it was higher than the corresponding bulk soil at any N treatments, thus promoting its P accumulation.【Conclusions】N application could effectively improve the up transportation and accumulation of P in the shoot of mining ecotype of Polygonum hydropiper, which are obtained by increasing the shoot biomass and the availability of soil P under high P condition. The optimal N application was 100 mg/kg in the pot experimental condition, and further experiment is needed for the practice of the remediation of P pollution in large scale.