Liming Fields Does Not Harm Soil

Madison, WI APRIL 19, 2011 – Liming soil is a common practice used in the agricultural process. Liming consists of spreading materials rich in calcium and magnesium onto fields in an effort to lower soil acidity, and promote microbial functionality and plant growth. While the liming process does facilitate efficient crop growth, the limestone used to produce the materials may host highly increased concentrations of toxic trace metals. Brown and black dendrites often appear on limestone rock and consist of iron and manganese oxides. These fossil-like formations are prized by mineral collectors but little is known about their chemistry and the potential for these toxic metals to end up in the soil has yet to be explored.

Scientists at the Johannes Gutenberg University at Mainz, Germany, recently examined the mobility of arsenic and copper found in dendrites of a local limestone. They particularly measured the binding forms of the toxic metals at a molecular level using synchrotron radiation. Soil pots were limed and weekly values of arsenic and copper were taken to estimate the total amount released while the soil was completely waterlogged, a condition notorious for arsenic mobility. Results obtain through x-ray absorption spectroscopy techniques indicated that both arsenic and copper were strongly bound to their dendrite oxides. No changes were observed between the altered and the unaltered soil. Researchers conclude that the toxins would only be released if the oxide dendrites were to be dissolved, an extremely unlikely scenario in the agricultural world. Therefore, limestone powder used for agricultural liming poses no significant threat to soils since the copper and arsenic are not likely to become bioavailable. Michael Kersten, the author of the study, stated, “Current legislative codes based solely on threshold values are of little help in case of dendrite-rich limestone. This research indicates that pollutant to iron or manganese ratios but not total pollutant amounts may be more useful in regulating the relatively harmless fertilizer impacts.” Kersten’s research is ongoing to investigate more binding forms of pollutants. Other geographical and climatic regions need to be assessed with other types of toxic metal pollutants and fertilizers. Results from the study are published in the March-April 2011 issue of the Soil Science Society of America Journal.

The full article is available for no charge for 30 days following the date of this summary. View the abstract at www.soils.org/publications/sssaj/abstracts/75/2/509.

Soil Science Society of America Journal, www.soils.org/publications/sssaj, is a peer-reviewed international journal published six times a year by the Soil Science Society of America. Its contents focus on research relating to physics; chemistry; biology and biochemistry; fertility and plant nutrition; genesis, morphology, and classification; water management and conservation; forest, range, and wildland soils; nutrient management and soil and plant analysis; mineralogy; and wetland soils.

The Soil Science Society of America (SSSA) is a progressive, international scientific society that fosters the transfer of knowledge and practices to sustain global soils. Based in Madison, WI, SSSA is the professional home for 6,000+ members dedicated to advancing the field of soil science. It provides information about soils in relation to crop production, environmental quality, ecosystem sustainability, bioremediation, waste management, recycling, and wise land use.

SSSA supports its members by providing quality research-based publications, educational programs, certifications, and science policy initiatives via a Washington, DC, office. Founded in 1936, SSSA celebrates its 75th Anniversary this year (2011). For more information, visit www.soils.org or follow @SSSA_soils on Twitter.