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Making the wasteland bloom

last modified Jan 28, 2014 02:48 PM
Making the wasteland bloom

Maize (Zea mays) Plants reaching maturity. Substrates left to right; Coal Waste amended with the organo-zeolitic biofertilizer, Coal waste, Garden soil, Coal waste amended with lime, Coal waste amended with zeolitic tuff.

Highly contaminated mine and refinery metal waste sites can remain barren of vegetation for many years.  In some cases the only solution has been to dump the contaminated soil into landfill, but it is much more environmentally friendly to regenerate the land.

Professor Leggo and his colleagues are working on a new strategy of soil amendment to greatly enhance the scope of plant growth on poor soils. A critical factor is how to supply sufficient plant nutrients to sustain growth. Biofertilizer seems to be the answer to this problem because, unlike synthetic chemicals, it provides a natural source of plant nutrients by greatly increasing the population of soil nitrifying micro-organisms. It is also a less expensive method of soil fertilization than synthetic agricultural chemicals and will not damage the soil environment.

Their current work is using coal waste as a substrate, as shown in the picture. They have shown that the biofertilizer is highly effective in producing enhanced growth and quality in six plant species; Miscanthus (Miscanthus giganticus), Ossier Willow (Salix viminialis), Maize (Zea maize), Sugar Beet (Beta vulgaris), Oil Seed Rape (Brassica napus) and Linseed (Linum usitatissimum).

The biofertilizer, or organo-zeolitic material, is a mixture of organic farm waste and crushed rock containing a common zeolite mineral called clinoptilolite. The farm waste (chicken manure in the present case) is composted together with the crushed rock and ammonium ions (NH4+), produced from the biological decomposition of the farm waste, are adsorbed to the zeolite surfaces. When this mixture is added to a soil, the ammonium ions are oxidized by nitrifying micro-organisms. This results in a large increase in soil nitrification which provides nitrate and other nutritional  elements to enhance plant growth and quality. 

Work on aqueous leachate from the plant substrates simulate the soil pore water chemistry and shows that nitrifying micro-organisms remain fully functional in metal polluted substrates, that are normally highly toxic to cellular organisms. Aqueous leachate analysis of the substrates amended with the bio-fertilizer have cation concentrations that are increased by two orders of magnitude relative to clean unamended soil, demonstrating the increase in abundance of nutritional elements.  Furthermore, in moist conditions, we have shown that the zeolite crystal surfaces become covered in biofilm (Leggo and Ledésert, 2006). Recent work has shown that bacteria enclosed in biofilm can survive and remain functional in highly metal polluted environments (Kemner et al., 2005). This, we believe accounts for the success we have had in sustaining the growth of plants (Arabidopsis halleri, Brassica napus and Salix viminalis ) in sediments that have extreme metal concentrations. 

Further information:

  • Leggo, P.J and Ledésert, B. 2006. The role of clinoptilolite in organo-zeolitic-soil systems used for phytoremedition. Science of the Total Environment 363: 1 - 10.
  • Kemmer, K.M et al. 2004. Elemental and Redox Analysis of Single Bacterial Cells by X-ray Microbeam Analysis. Science, Vol 306, Issue 5696: 686-687.