Page 158 - Enzymes in Tropical Soils

146 Enzymes In Tropical Soils

Biochars was reported to adsorb several substances, ranging from
herbicides to plant-inhibiting allelochemicals such as heavy metals (Buss et al.,
2012). Buss et al. (2012) reported that the presence of biochars decreased the Cu
entering the plant tissues in the order of roots, shoots, and leaves. The most
probable ameliorating mechanisms were the adsorption of Cu onto the negatively
charged biochar surfaces. Thereby, application of biochars may lower the Cu
toxicity to plants. Ippolito et al. (2012) also reported that biochars adosrbed
increasing-amounts of Cu as the soil solution pH decreased from 9 to 6.

Compost 0

0
Soluble Cu Compost 1

Compost 2

Compost 3

Lime 0 Lime 1 Lime 2 Lime 3

Fig. 9.12. The decrease in soluble Cu of industrial waste by lime and cassava-leaf compost
(Adapted from Salam et al., 1998a).

Other than the addition of lime and/or organic matters, heavy metals in the
soil environment can also be attenuated by employing some other materials and
processes. For example, phosphatic rocks and phosphatic fertilizers may be used
through adsorption heavy metals by phosphatic substances or precipitation to be
phosphatic secondary minerals (Rabinowitz, 1993; Ruby at al., 1994; Ma et al.,
1993; 1994; 1995; Brown et al., 2004; Moseley et al., 2008; Kilgour et al., 2008;

Abdul Kadir Salam - 2014