Pedosphere 26(1): 1–12, 2016 doi:10.1016/S1002-0160(15)60017-0 ISSN 1002-0160/CN 32-1315/P c ⃝ 2016 Soil Science Society of China Published by Elsevier B.V. and Science Press Natural Organic Amendments for Improved Phytoremediation of Polluted Soils: A Review of Recent Progress Alina WISZNIEWSKA 1,* , Ewa HANUS-FAJERSKA 1 , Ewa MUSZY ´ NSKA 1 and Krystyna CIARKOWSKA 2 1 Institute of Plant Biology and Biotechnology, Faculty of Biotechnology and Horticulture, University of Agriculture, Krak´ ow 31-425 (Poland) 2 Department of Soil Science and Soil Protection, Faculty of Agriculture and Economics, University of Agriculture, Krak´ ow 31-120 (Poland) (Received March 30, 2015; revised October 29, 2015) ABSTRACT Environmental pollution caused by metals, radionuclides and organic pollutants affects quality of the biosphere: soil, water and air. Currently, great efforts have been made to reduce, remove or stabilize contaminants in polluted sites. There has been increasing interest in phytoremediation—the use of plants to reduce concentration of pollutants or to render them harmless. This paper provides a brief review of recent progress in the research and practical application of phytoremediation techniques. Improvements in phytoremediation due to utilization of organic amendments, namely, agro- and industrial wastes (such as sugar beet residue, composted sewage sludge or molasses), biochar, humic substances, plant extracts and exudates are discussed, as well as their influences on soil structure and characteristics, plants growth and bioavailability of pollutants. Both plant-assisted phytoremediation and the use of natural materials in the absence of remediating plant are believed to be cost-effective and environmentally friendly approaches for soil cleanup. However, the characterization and quantification of a range of natural materials used in phytoremediation are essential in order to implement these approaches to practice. Key Words: agricultural wastes, bioavailability, biochar, contamination, natural chelators, toxic elements Citation: Wiszniewska A, Hanus-Fajerska E, Muszy´ nska E, Ciarkowska K. 2016. Natural organic amendments for improved phytore- mediation of polluted soils: A review of recent progress. Pedosphere. 26(1): 1–12. INTRODUCTION Contamination of agricultural environment has be- come a serious global problem (Ji et al., 2011; Bech et al., 2012; Choi et al., 2013). Therefore, it is nece- ssary to improve methods for removing, reducing or mitigating toxic substances introduced into soil via an- thropogenic activity. Traditional methods of soil reme- diation, such as liming, washing, leaching, turning and deep plowing, are usually energy-consuming and re- quire expensive machinery that often causes secondary pollution (Cunningham and Ow, 1996; Park J H et al., 2011b). Phytoremediation exploits the abilities of green plants to uptake pollutants. It can be defined as the combined use of plants and agronomic prac- tices to remove contaminants from the environment or to decrease their toxicity. Techniques applied in phy- toremediation can be cost-effective, aesthetically plea- sing and may require smaller disposal facilities. More- over, such treatment causes only minimal environmen- tal disturbance, thus remediated medium can directly be used for the agricultural purposes (Salt et al., 1998; Evangelou et al., 2004; Merkl et al., 2005). It is also possible to remove air pollutants using an appropriate plant material (Ciarkowska and Hanus-Fajerska, 2008; Ji et al., 2011; Ali et al., 2013). Techniques of phytore- mediation, i.e., phytoextraction, phytofiltration, phy- tostabilization, phytodegradation, phytovolatilization and phytodesalination, are summarized in Table I. Strategies aimed at increasing the effectiveness of phytoremediation are reviewed in this paper with a special attention paid to use of the organic amend- ments to facilitate both soil cleanup and the growth of phytoremediation plants. CLASSICAL APPROACH—USE OF HYPERACCU- MULATORS AND SYNTHETIC CHELATORS Selected plant species and ecotypes are able to ac- cumulate and tolerate high levels of trace elements (Baker and Brooks, 1989; Reeves, 1992; Reeves et al., 1999, Ciarkowska and Hanus-Fajerska, 2008; Faucon ∗ Corresponding author. E-mail: a.wiszniewska@ogr.ur.krakow.pl.