An ancient agricultural practice finds a place in modern agricultural practices to remediate farm fields contaminated with heavy metals
Lay summary by Sam Nutile
An ancient agricultural technique, known as slash-and-char, may serve as a means of remediating agricultural fields contaminated with heavy metals. By combusting agricultural waste biomass at low temperatures and mixing the resulting biochar into the soil, soils contaminated with high levels of heavy metals may once again become productive sources of agriculture around the world.
Heavy metals, such as copper, zinc, and lead, are found in agricultural environments in developing and established countries around the world. Their environmental persistence and tendency to accumulate in the edible portions of plants makes growing and harvesting crops from these environments challenging and can lead to human exposure. Although methods exist to remediate agricultural fields suffering from heavy metal contamination, the costs and efficiency of these methods can severely limit their application.
Conversely, slash-and-char, an ancient agricultural practice, may offer an easy, cost-effective technique to alleviate metal contamination and reclaim unusable or tainted agricultural land. To reintroduce this technique into modern agricultural practices, Niu et al. set out to discover the ability of slash-and-char methods to immobilize heavy metals in soil, increase crop production in heavy metal contaminated soils, and reduce the amount of heavy metals taken up by vegetables grown in these soils.
By combusting rice stalks left over from harvest, the researchers applied the slash-and-char technique to a soil that has been contaminated with high levels of heavy metals. Soils treated by slash-and-char had reduced bioavailable heavy metal concentrations compared to untreated soils. Treated soils also showed higher growth rates and reduced metal concentrations in the edible parts of vegetables grown, both increasing production and reducing human exposure.
With the global population ever increasing and world hunger already a concern, reclaiming land contaminated with heavy metals is imperative to ensure agriculture can continue at a suitable rate to match population growth. Slash-and-char offers an easy, cost-effective, and eco-friendly technique to reclaim agricultural land contaminated with heavy metals. Reducing the bioavailability of these toxins in soils reduces human exposure through consumption of food crops, as well as increases the soil’s productivity. Although more research into the types of agricultural wastes that can be used with slash-and-char and the extent of heavy metal contamination that can be controlled is needed, this ancient agricultural technique may have once again found a place in agricultural practices of the world today.
For further information
Read the Environmental Pollution original research article which this summary is based on Slash-and-char: An ancient agricultural technique holds new promise for management of soils contaminated by Cd, Pb and Zn (October 2015).
Visit the profile of the research ambassador, Sam Nutile, who wrote this summary.
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