Abstract:

To select suitable in situ remediation measures for mild to medium Cd-contaminated wheat field in north China, the repair effects of seven kinds of conditioners and three kinds of cultivation measures were compared. A Cd-contaminated field caused by wastewater irrigation in northern Henan Province was taken as the research farmland, and the experiment was conducted in the wheat-growing season. The conditioners included calcium fertilizer, silicon fertilizer, calcium superphosphate, calcium-magnesia phosphate fertilizer, biochar, and bone charcoal. The cultivation measures included deep tillage, deep loosening, and dense planting. Foliar fertilizer was also applied in the experiment. The results showed that compared with the control, calcium superphosphate treatment was the most effective in the increase of soil pH as well as the decrease of soil available Cd, root Cd and grain Cd. Though the reducing effect of calcium fertilizer on soil Cd and grain Cd was second only to that of calcium superphosphate, its role in lowering shoot Cd was the most significant. Silicon fertilizer effectively suppressed Cd transportation from roots to the aboveground parts. Calcium-magnesia phosphate fertilizer enhanced the yield most obviously. Deep tillage measure was the most efficient in increasing total root length in soil of 20-40 cm, and it was also functional in lowering Cd in soil and different plant tissues to some degree, which was also true for biochar treatment. Though bone charcoal and foliar fertilizer treatment did not reduce the root Cd, they lowered the shoot and grain Cd. Deep loosening and dense planting did not work in the remediation. More unexpectedly, dense planting treatment increased soil available Cd. The factors associated with grain Cd most strongly were shoot Cd content and soil pH. Taking remediation effect and cost into consideration, the application of calcium superphosphate is one of the best choice for the remediation of Cd-contaminated wheat field in north China.

Key words: conditioners, cultivation measures, soil, cadmium, wheat