Mays, D.A. and J.J. Mortvedt.  1986.  Crop response to soil applications of phosphogypsum.  J. Env. Qual. 15:78-81.

The effects of three rates of phosphogypsum on crop growth and uptake of cadmium and radium were assessed.  It was found that PG may be applied to agricultural soils at relatively high application rates (up to 112 tonnes/ha) without increasing levels of Cd or radioactivity in corn, wheat or soybean grain.

Million, J.B., J.B. Sartain, R.X. Gonzales and W.D. Carrier III.  1994.  Radium-226 and calcium uptake by crops grown in mixtures of sand and clay tailings from phosphate mining.  J. Env. Qual. 23:671-676.

Studies were conducted to evaluate radium concentrations in plant tissue as affected by sand/clay phosphate tailings mixtures, organic amendments and phosphogypsum.  It was found that PG (up to 134 tonnes/ha) had no effect on the radium concentration or yield of any grown vegetable or alfalfa.  Phosphogypsum did increase the amount of extractable soil Ca, but had little effect on plant Ca concentration.

Liang, J., R.E. Karamanos and M.E. Moir.  1995.  The influence of brine contamination and phosphogypsum amendments on soil chemical properties and plant response.  Commun. Soil Sci. Plant Anal. 26(7&8): 1033-1057.

Phosphogypsum was found to be an effective soil conditioner for sodic, solonetz and solonetzic soils (up to 400 tonnes/ha), and an effective means of remediating brine spills, resulting in increased plant growth.  There was no evidence that PG increased the level of trace elements in plants or that there was little, if any, potential for movement of trace elements into greater depths.

Sumner, M. E.  1996.  Application rates of phosphogypsum in agriculture.  Proceedings of the Phosphogypsum Fact-Finding Forum, Florida Institute of Phosphate Research (FIPR), Dec 7, 1995.

This report summarizes application rates for PG to fulfill the Ca requirements of various crops, in reclaiming sodic soils, in reducing crusting and improving seedling emergence and in reducing mechanical impedance.  Average rates for these uses are in the range of 100 to 500 lb/ac.  Dr. Sumner states that when phosphogypsum has been used, radiation has not significantly increased above native background levels, and that no significant differences in plant uptake of radionuclides could be detected due to PG treatment.

Roessler, C.E.  1988.  Radiological Assessment of the Application of Phosphogypsum to Agricultural Land.  Proc. 2nd Intl Symp on Phosphogypsum.  Florida Institute of Phosphate Research.

This article shows the expected radium 226 levels in soils from 1 ton/acre application rates, uptake by grain crops and expected radiation doses to humans.  It concludes that “there is no significant problem associated with the proposed application of phosphogypsum to grain crop lands for periods up to tens of years”.

Roessler, C.E. et al.  1996.  Radiological assessment of the application of phosphogypsum to Florida forage lands. Proceedings of the Phosphogypsum Fact-Finding Forum, FIPR, Dec 7, 1995.

Phosphogypsum was applied to forage lands at rates of up to 1.8 tons/ac (4 tonnes/ha).  Radiological effects could not be measured with a degree of confidence, so a second phase was initiated with higher PG rates - up to 8.9 tons/acre.  It was found that a single treatment of PG at agronomic rates cannot be detected with current analytical methods;  after 100 years of annual treatment, the projected added radionuclide concentrations are roughly equal to the existing background at the test sites and within the range of variations seen in Florida land.

Miller, W.P.  1995.  Environmental considerations in land application of by-product gypsum.  pp. 183-208 in Agriculture Utilization of Urban and Industrial By-products, Karlen, D.L, et al., eds. ASA Special Publ. 58.

Total concentrations of most metallic cations, including Cd, Pb, Cr, Ni, Cu, Zn and Hg are relatively low;  compared to other land-applied materials such as sewage sludge, PG metal concentrations are lower by an order of magnitude or more.  The application of PG therefore has little impact on the total metal load in agricultural soils.  Similarly, plant uptake of these elements should not be impacted by gypsum applications except in very unusual circumstances.

Alcordo, I.S. and J.E. Rechcigl.  1993.  Phosphogypsum in Agriculture:  A Review.  Adv. Agron. 49:55-118.

An extensive review of the use of phosphogypsum in agriculture.  In terms of environmental considerations, the authors conclude;  “Radionuclides, heavy metal impurities, and other pollutants at concentrations found in phosphogypsum do not appear to constitute environmental hazards to surficial groundwater, crop tissue, and the ambient atmosphere at the rates normally used in agriculture.  Based on currently available information, phosphogypsum appears to be an environmentally safe source of S and Ca for crops as well as for other uses”.

Alcordo, I.S. and J.E. Rechcigl.  1995.  Phosphogypsum and other By-product Gypsums.   pp. 365-425 in Soil Amendments and Environmental Quality, J.E. Rechcigl, ed.  CRC Lewis Publishers, New York.

Another extensive review of phosphogypsum use and environmental aspects.  It concludes that the toxic metals and fluorides in industrial by-product gypsums do not appear to constitute environmental hazards to surficial groundwater, soil and crop tissue at rates used in agriculture.  Almost all studies show little or no statistically measurable radiological effect in crops, soil, groundwater and atmosphere.

Al-Oudat, M., A. Arslan and S. Kanakri.  1998.  Physical and chemical properties, plant growth and radionuclide accumulation effects from mixing phosphogypsum with some soils.  Comm. Soil Sci. Plant Anal., 29:2515-2528.

This study examined PG rates of up to 25% to mimic the effects of adding 5T ha-1 to local soils for 100 consecutive years.  Addition of PG was found to substantially increase plant growth and improve soil chemical and physical properties.  The radioactivity of plants grown in the mixtures were below the analytical detection limits in all treatments.