Field phytoremediation of slightly cadmium-contaminated farmland by intercropping Amaranthus hypochondriacus with the medicinal crop Bletilla striata : remediation efficiency and cost–benefit assessment

Phytoremediation is a promising approach for remediating cadmium (Cd)-contaminated farmland, but its application is often limited by long remediation periods and low economic returns. Integrating Cd-accumulating plants with high-value crops may help balance contaminant removal with agricultural profitability. Three candidate Cd-accumulating plants were first evaluated in the field, and the selected species was subsequently intercropped with the medicinal plant Bletilla striata in a two-year experiment conducted on slightly Cd-contaminated farmland. Among the tested species, A. hypochondriacus exhibited the highest Cd extraction capacity (90.94 g ha−1), which was 9.49 and 2.60 times greater than those of Solanum nigrum and Hylotelephium spectabile, respectively. Relative to monoculture, the intercropping system decreased Cd concentration in B. striata tubers by 25.64%, increased equivalent tuber yield by 35.52%, and improved equivalent Cd extraction by A. hypochondriacus by 27.69%. A ten-year economic assessment showed that the intercropping system achieved cost recovery within five years, compared with eight years for A. hypochondriacus monoculture. These findings suggest that A. hypochondriacus–B. striata intercropping represents a promising phytomanagement strategy for simultaneously achieving Cd remediation and economic benefits in slightly Cd-contaminated farmland.