[Plant growth and Cd accumulation characteristics in different planting modes of maize and Amaranthus...

To achieve the goal of remediation while producing for farmland contaminated by Cd, maize and grain amaranth (Amaranthus hypochondriacus) were planted on farmland contaminated by Cd in five different intercropping modes, including alternating wide-narrow-row of maize and single-row grain amaranth intercropped between wide rows (T₁), alternating wide-narrow-row of maize and double-row grain amaranth intercropped between wide rows (T₂), equidistant double-row maize and single-row grain amaranth intercropped between rows (T₃), equidistant double-row maize and double-row grain amaranth intercropped between rows (T₄), maize and grain amaranth intercropped with equal four rows (T₅), while maize (CK₁) and grain amaranth (CK₂) single planted as control to explore the effects of different intercropping modes on growth and Cd accumulation of crops and hyper-accumulation plants (A. hypochondriacus). The results showed that: 1) Compared with mono-culture (CK₁), grain yield of maize per plant showed an increasing trend in intercropping modes. The grain yield of maize in T₁ increased by 10.5%, while that in T₄ and T₅ decreased by 6.3% and 5.4% respectively, and that in T₂ or T₃ did not change compared with monoculture of maize. The aboveground biomass per plant and yield per unit area of grain amaranth decreased by 69.5%-95.7% and 83.9%-96.9% in intercropping modes respectively compared with monoculture (CK₂). 2) The Cd content of maize grain showed an increasing trend in intercropping modes compared with monoculture (CK₁). The Cd content of grain amaranth showed a decreasing trend in intercropping modes compared with monoculture (CK2). 3) Compared with monoculture (CK2), the enrichment coefficient, transport coefficient, and effective transport coefficient of grain amaranth all showed an increasing trend in intercropping modes, while the aboveground Cd extraction amount per plant and per unit area of grain amaranth decreased by 40.4%-86.7% and 70.4%-88.9% in intercropping modes, respectively. The total amount of Cd extraction per unit area of maize and grain amaranth in intercropping modes was significantly higher than that in monoculture of maize and lower than that in monoculture of grain amaranth. 4) The content of available Cd in maize rhizosphere soil and the content of total/available Cd in grain amaranth rhizosphere soil both showed an increasing trend in intercropping modes compared with monoculture of both crop, but it had no significant effect on non-rhizosphere soil. In this study, T₁ was beneficial to increase maize grain yield, while T₅ was beneficial to maximize the Cd extraction amount of grain amaranth.