Growth, survival, and heavy metal (Cd and Ni) uptake of spinach (Spinacia oleracea) and fenugreek (Trigonella corniculata) in a biochar-amended sewage-irrigated contaminated soil Uzma Younis 1 , Muhammad Farooq Qayyum 2 *, M. Hasnain Raza Shah 1 , Subhan Danish 2 , Ahmad Naeem Shahzad 3 , Saeed Ahmad Malik 1 , and Seema Mahmood 1 1 Institute of Pure and Applied Biology, Bahauddin Zakariya University, Multan, Pakistan 2 Department of Soil Science, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University Multan, Pakistan 3 Department of Agronomy, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University Multan, Pakistan Abstract Irrigation of arable land with contaminated sewage waters leads to the accumulation of trace metals in soils with subsequent phyto-/zootoxic consequences. In this study, biochar derived from cotton sticks was used to amend an agricultural silt-loam soil that had been previously irri- gated with trace metal contaminated sewage waters. Metal accumulation and toxicity to spinach (Spinacia oleracea) and fenugreek (Trigonella corniculata) was investigated by measuring con- centrations of Cd and Ni in plant tissues and various photosynthetic and biochemical activities of plants. Positive impacts of biochar on both spinach and fenugreek were observed in terms of bio- mass production that increased from 29% to 36% in case of spinach, while for fenugreek this in- crease was 32% to 36%. In the control treatment there was an increase in malondialdihyde, solu- ble sugar, and ascorbic acid contents, indicating heavy metal stress. Biochar applications in- creased soluble proteins and amino acids in plants and reduced the uptake of Cd from 5.42 mg kg –1 at control to 3.45 mg kg –1 at 5% biochar amended soil and Ni (13.8 mg kg –1 to 7.3 mg kg –1 at 5% biochar) by the spinach plants. In fenugreek, the Cd was reduced from 7.72 mg kg –1 to 3.88 mg kg –1 and reduction in Ni was from 15.45 mg kg –1 to 9.46 mg kg –1 at 5% biochar treated soil, reducing the possibility of transfer up the food chain. This study demonstrates that the use of biochar made from cotton-sticks, as an amendment to arable soils that have received contami- nated irrigation water, could improve plant growth and decrease Cd and Ni uptake to crops, alle- viating some of the negative impacts of using sewage waters on arable land. Key words: vegetables / trace metals / biochar / physiological attributes Accepted October 16, 2014 1 Introduction Enormous growth of the human population over the last cen- tury has substantially increased the global use of fresh water, simultaneously generating huge quantities of waste waters. In most countries waste water is treated to eliminate pathogens, reduce heavy metal contents, and reduce the environmental impact of discharging contaminated waters. In Pakistan, sur- rounding various cities, sewage water is often used to irrigate lands to grow vegetables (Khalil and Kakar , 2011), a practice which is driven by the fact that sewage water is readily avail- able locally, cheap and provides some essential nutrients to crops. But the continuous use of sewage water for irrigation has led to the accumulation of pollutants such as heavy met- als in arable soils (Murtaza et al., 2003). At low concentra- tions, some metals increase plant physiological and biochem- ical activities, such as enhancing production of metabolized products, e.g., glutathione (GSH), oxalic acid, histidine, cit- rate, and metal-binding proteins (Zhang et al., 1999). How- ever, at high metal concentrations plant toxicity can result in disturbing metabolism and photosynthesis (Zhao and Bi, 1999). In general, toxicity of certain heavy metals such as Cd, Ni, and Pb reduces photosynthesis by affecting stomatal opening (Bazzaz et al., 1974). As well as impacting on crop yields, crop quality can also be affected by heavy metals in soils by increasing metal concentration in plant tissues; the in- gestion of certain heavy metals such as Cd and Pb in excess amounts can be carcinogenic (Radwan and Salama, 2006) and cause serious cardiovascular, renal and neuronal disor- ders in humans (Jarup, 2003; Steenland and Boffetta, 2000; WHO, 1992). Therefore, to avoid the entry of heavy metals into the food chain either the source of contamination or the pathway by which it reaches humans should be eliminated or disrupted. Immobilization of the metals in situ through various soil amendments is one of the most convenient methods of reduc- ing the impact of metals on plants at relatively low cost (Bees- ley et al., 2014; Brown et al., 2005; Cao and Ma, 2004; Gade- palle et al., 2009; Warren et al., 2003). These amendments may include inorganic (gypsum, elemental sulfur, zeolite, etc.) or organic (compost, farm manure, biochar, etc.) treat- ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.plant-soil.com J. Plant Nutr. Soil Sci. 2015, 000, 1–9 DOI: 10.1002/jpln.201400325 1 *Correspondence: Dr. M. F. Qayyum; e-mail: Farooq.qayyum@bzu.edu.pk