Cadmium phytoavailability from 1976 through 2016: Changes in soil amended with phosphate fertilizer and compost

This study aimed to determine cadmium (Cd) accumulation in arable soil, changes in Cd extractability and relevant soil properties, and Cd uptake by rice plants after long-term (50 years) application of phosphate (P) fertilizer and compost. A long-term field experiment was performed with rice crops from 1967 to 2016. Treatments included nitrogen and potassium fertilization (NK), nitrogen, phosphate, and potassium fertilization (NPK), nitrogen, phosphate, and potassium fertilization with compost application (NPK + compost), and control. Total Cd concentration in soil amended with NPK and NPK + compost continuously increased from 110 μg kg^-1 up to 232 μg kg^-1 from 1976 to 2016 but remained unchanged in control soil and soil amended with only NK. Plant-available Cd concentration in soil increased with year for all treatments, likely as a result of relevant changes in soil chemical properties. Cd concentrations in rice harvested in 2017 treated with NPK or NPK + compost were 212 μg Cd kg^-1 and 223 μg Cd kg^-1, respectively. These values exceed the maximum permissible level (200 μg Cd kg^-1) established by the Ministry of Food and Drug Safety of Korea.