Maize–Potato Intercropping: Application Potential of Conventional Tillage Pattern for Safe Production in High-Geological-Cadmium Background Farmland

Traditional intercropping systems represent an economically feasible and sustainable strategy for the safe utilization of cadmium (Cd) contaminated farmland. To assess the safe production potential of a maize potato intercropping system in high-heological-Cd background agricultural areas, four planting patterns were set up in the Chongqing karst area, China: maize monoculture (T1), maize–potato intercropping with a 1:1 row ratio (T2), maize–potato intercropping with a 2:2 row ratio (T3), and potato monoculture (T4). We systematically compared soil pH, total Cd, and available Cd across the different planting patterns. Cd concentrations were determined in multiple organs of the two crops: roots, stems, nodes, leaves, husks, cobs, and grains for maize; and roots, stems, leaves, and tubers for potato. Furthermore, Cd bioconcentration factors (BCF), translocation factors (TF), dietary health risks posed by edible organs, and economic benefits under each cropping system were analyzed. The results revealed that: (1) Maize and potato cultivation modified the microenvironment of the soil surrounding the roots. Total and available Cd concentrations in the soil surrounding potato roots were lower than those in the soil surrounding maize roots, although the difference was not significant (p < 0.05). (2) Compared with potato monoculture, 1:1 and 2:2 row ratios of maize–potato intercropping significantly reduced Cd concentrations in fresh potato tubers by 38.81% and 38.01%, respectively; tuber Cd concentrations complied with the national food safety limit. (3) Marked interspecific differences were observed in Cd accumulation and translocation traits between maize and potato. The bioconcentration factor (BCF) of all maize organs was below 1, and Cd concentration and accumulation capacity exhibited a decreasing gradient trend following the order: roots > leaves > nodes > husks ≈ stems > cobs > grains. For potato, the BCF values of roots, stems, leaves, and tubers were all greater than 1, and their Cd accumulation capacities were 9.13-, 67.33-, 20.84-, and 37.67-fold higher than the respective organs of maize, respectively. (4) Based on health risk assessment and economic benefit evaluation, the two maize potato intercropping systems (T2 and T3) achieved substantially higher combined economic returns than maize monoculture (T1), while presenting markedly lower dietary health risks than potato monoculture (T4). This case study validates the hypothesis that maize–potato intercropping alters cadmium translocation and distribution responses within the soil–crop system, and demonstrates its potential to improve farmland economic benefits while guaranteeing agricultural product safety. Consequently, these intercropping patterns represent a promising strategy for promoting safe and green production on High-Geological-Cd background farmland.