RESEARCH ARTICLE Effects of different soil pH and nitrogen fertilizers on Bidens pilosa L. Cd accumulation Huiping Dai 1 & Shuhe Wei 2 & Lidia Skuza 3 Received: 10 September 2019 /Accepted: 29 December 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Bidens pilosa L. was a Cd hyperaccumulator. This experiment determined the effects of different soil pH (adjusted by weak acid and alkali at 4.83, 6.81, and 7.84, respectively) and nitrogen ((NH 4 ) 2 SO 4 , Ca(NO 3 ) 2 ) on B. pilosa phytoextracting Cd in soil collected from a smelter (Cd concentration was 19.63 mg kg -1 ). The results showed that the Cd concentrations in B. pilosa were significantly higher (p <0.05) with soil pH 4.83 treatments than those of pH 6.81 and 7.84 ones. The Cd concentration of B. pilosa grown in pH 7.84 soil was significantly lower (p < 0.05) than that in pH 6.81 soil. The extractable Cd concentration in soil was decreased (p < 0.05) with the increase of pH. Under three different pH conditions, the rhizosphere pH of B. pilosa was basically 0.2 lower than that of pH in bulk soil respectively, indicating that the hyperaccumulator had a certain acidification effect on soil. Two kinds of nitrogen fertilizers (NH 4 ) 2 SO 4 and Ca(NO 3 ) 2 had no significant difference (p < 0.05) on Cd concentrations of B. pilosa, which was probably caused by the acidification effect of its rhizosphere. The biomasses of B. pilosa were not affected (p < 0.05) by different pH of soil. The photosynthetic production, antioxidative enzymes, and lipid peroxidation change trends of B. pilosa were basically consistent with its biomasses. Generally speaking, B. pilosa showed high Cd accumulation potential and strong adaptability for different soil situations. Keywords Bidens pilosa L. . Hyperaccumulator . pH . Nitrogenous fertilizer . Phytoremediation Introduction The hyperaccumulator has strong ability to phytoextract heavy metals in contaminated soils. Thus, these heavy metal contaminated soils could be remediated by planting and re- moving such hyperaccumulating plants (van der Ent et al. 2013). However, the removal rates of heavy metals from pol- luted soils by published hyperaccumulators had not reached the expected level until now (Li et al. 2012a). Many studies had been carried out to promote the enrichment of heavy metals in polluted soils by hyperaccumulators. Generally speaking, there were two main ways to promote the accumu- lation of heavy metals in hyperaccumulators. One was to in- crease the concentrations of heavy metals without reducing the biomass of hyperaccumulators. The second was to in- crease the biomass without reducing the heavy metal concen- tration accumulated by hyperaccumulators. Of course, in- creasing biomass and heavy metal concentration at the same time was the ideal way. Some methods were used to increase the biomass of hyperaccumulator such as added endophytic bacterium SaMR12 (Pan et al. 2017) and elevated CO 2 concentration to improve root growth and Cd accumulation in the hyperaccumulator Sedum alfredii Hance (Li et al. 2012b). However, more researches had been done on the application of fertilizers to improve the biomasses of hyperaccumulators (Wei et al. 2015; Yang et al. 2019). Among the common fer- tilizers, nitrogen, phosphorus, and organic fertilizers could also significantly increase plant biomass, but they had a sig- nificant passivation effect on heavy metal accumulation by hyperaccumulators. In comparison, nitrogen fertilizer has a Responsible editor: Elena Maestri * Shuhe Wei shuhewei@iae.ac.cn 1 College of Biological Science & Engineering, Shaanxi Province Key Laboratory of Bio-resources, Shaanxi University of Technology, Hanzhong 723001, China 2 Key Laboratory of Pollution Ecology and Environment Engineering, Chinese Academy of Sciences, Institute of Applied Ecology, Shenyang 110016, China 3 Institute of Biology, University of Szczecin, 71-415 Szczecin, Poland Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-07579-5