Keywords: Cadmium, Soybean (Glycine max), Agronomy, Soil contamination, Protein security
Little is known about soybean (Glycine max [L.] Merr.) growth and yield responses to cadmium contamination of agricultural soil. Three levels of cadmium ecological screening values (2 CdCl2 ESV, 4 CdCl2 ESV and 6 CdCl2 ESV) were used to contaminate trial soils before sowing viable seeds from ten soybean accessions. The plants were monitored for growth, physiological characteristics and seed yield. Results showed significant growth impairment in G. max that was proportional to soil CdCl2 contamination levels. There was 30% yield reduction at CdCl2 2 ESV and < 50% yield reductions at 6 CdCl2 ESV. Accession TGm-941 had the highest yield in the control but showed a 40% yield reduction upon exposure to cadmium contamination. Morphologically, the shapes and outer appearance of some harvested soybean seeds were distorted, which is likely due to elevated cadmium levels in the soil. The mechanisms attributable to these changes are not known and require further investigation. Soybean is capable of tolerating low levels of cadmium contamination by maintaining growth and limited yield reduction but higher levels of contamination significantly reduced plant growth and yield.
The authors are grateful to the International Institute for Tropical Agriculture, Ibadan, Nigeria and Department of Plant Biology and Biotechnology, University of Benin, Nigeria for providing us with the soybean seeds used in the study and space in the botanical garden for the experiment, respectively.