Effectiveness of biochar for increasing soil quality and reducing metal bioavailability of three different soils

Wien

2014

S. 22-23

Artikel aus einer ZeitschriftUnselbständiges Werk

200190146

Intensive agriculture and industrial activities have led to a general decline of soil quality in the last decades. In this context, the loss of organic matter in soils and the contamination with heavy metals are two major problems. Since large areas are affected, low-cost and environmentally friendly approaches are needed for the remediation of degraded or polluted soils. The application of amendments may improve the soil quality, increase productivity and reduce the bioavailability of pollutants. In the research project "NAWAROSAN", co-funded by the Austrian Research Promotion Agency (FFG), biochar amendments are tested on two agricultural soils low in organic matter and one agricultural soil contaminated with Pb, Zn and Cd. On the two depleted soils, N and C balance as well as biomass yield are in main focus. Whereas in case of the contaminated site, the study aims towards heavy metal stabilization in the soil along with the cultivation of an excluder plant for renewable biomass production. According to preliminary results, treatments for a two year field experiment and a greenhouse - pot experiment were selected as follows: (i) Biochar from fibre sludge and cereal husk; (ii) Poplar wood chips biochar; both types enriched with compost and nitrogen ((NH4)2SO4). Additionally, a (iii) 50:50 mixture of gravel sludge andsiderite bearing was applied on the contaminated site. Either Miscanthus or maize was planted on the sites as well as in the greenhouse in springand harvested in autumn 2013. Relevant analysis targeting shoot biomass, extractable metal concentrations (Cd, Pb, Zn), nitrogen supply and organic matter content were undertaken in both, plant and soil samples. So far, a reduction of extractable Zn (NH4NO3) from 181 mg kg-1 to 81 mg kg-1, 96 mg kg-1 and 103 mg kg-1 in the gravel sludge/ siderite bearing treatment, the poplar biochar and gravel sludge / siderite bearing combination and the poplar biochar treatment, respectively compared to the control, was shown. The plant analyses did show not significant differences between the single treatments regarding the metal incorporation into the biomass. In the field trial, a relative increase in maize yield was observed in the biochar treatment on the humus-depleted soil (up to 50%) in comparison to the mineral-fertilized control. On the contrary, the biochar treatments did not increase the biomass growth on the contaminated soil. These findings indicate differential effects of the different amendments on biomass productivity as well as the reduction of the bioavailability of the metals. Moreover, the Ct and Nt analysis did not show any relevant differences among the treatments yet. Further tests will provide more data on relevant metal concentration changes in soil and plant as well as on nutrient and carbon supply of the first year of the main experiment. More information on the long-term effectiveness of the tested amendments will be provided in the second year.