The influences of lignin application on soil properties of three different soils, Jiangxi soil (Ultisol, Hapludult), Heilongjiang soil (Alfisol, Entioboralf) and Beijing soil (Alfisol, Haplustalf), and metal accumulation in wheat (Triticum aestivum L.) were studied in a pot experiment. By lignin amendment, soil pH, organic matter (OM) and cation exchange capacity (CEC) increased, except for CEC in the Beijing soil. Analysis showed that available P and K in lignin-amended soils were also elevated, except for P in the Jiangxi soil. A three-step sequential extraction procedure proposed by the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission was used to investigate the fraction redistribution of heavy metals in soils with lignin application. The fractions were specified as B1: water soluble, exchangeable and carbonate bound, and weakly adsorbed; B2: Fe-Mn oxide bound; and B3: organic matter and sulfide bound. Generally, the heavy metal content of the B2 fraction decreased whereas that of the B3 fraction increased. Lignin application to arable soils can not only improve plant growth in vitro, but also reduce the accumulation of the heavy metals Cu, Zn, Cd, Pb, Cr and Ni in wheat plants.

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Lignin is a primary byproduct from the black liquor treatment in paper making industries, its application as micro-fertilizer in agricultural land might provide a promising alternative to sewage discharge. However, application of such a micro-fertilizer might affect the soil properties and result in soil pollution. In this study, the effects of lignin application on phyto-availability and speciation change of heavy metals in soils were investigated. Greenhouse experiments showed that lignin application improved the growth of winter wheat (Triticum aestivum L.) in all three soils investigated. The increase of the biomass for wheat shoot was 59.7%, 39.8% and 12.3% for Beijing soil, Jiangxi soil and Dongbei soil, respectively. In contrast, lignin amendment decreased the concentrations of heavy metals in wheat shoots from 2.2% to 61.0%. Sequential extraction procedure of a three-step BCR was used to investigate the fraction distribution. The extractable fractions were specified as fraction B1: water soluble, exchangeable and carbonate bound or weakly specifically adsorbed; B2: Fe-Mn oxide bound; B3: organic matter and sulfide bound. The results showed that lignin application led to the redistribution of heavy metals in each fraction. Generally, heavy metals decreased in B1 and B2 fractions and increased in B3 fraction. Upon the results short-term application of lignin in agricultural land not only improves the growth of wheat but also reduces the phyto-abailability of heavy metal in wheat.