[Effects of Irrigation Techniques on Migration and Accumulation of Cd and As in a Calcareous Soil-wheat System]

In order to clarify the effects of flood irrigation （FI）， sprinkler irrigation （SI）， and drip irrigation （DI） on the accumulation of cadmium （Cd） and arsenic （As） in wheat grains， a mini-plot experiment was carried out to investigate the variations of soil Cd and As bioavailability in the rhizosphere under three irrigation treatments （DI and SI with the same irrigation volume， both equal to two-thirds of FI） and the distribution， migration， and accumulation of Cd and As in various parts of winter wheat. The results showed that the DI treatment reduced grain-Cd by 22.14% and grain-As by 17.46% and the accumulation of Cd by 32.09% and As by 27.77% in wheat grains and did not decrease the hundred-grain weight and grain number per spike compared with that in FI. Furthermore， it was found that the DI treatment decreased soil Eh and then regulated the composition of dominant rhizobacterial genera. DI reduced the relative abundance of unclassified_o__Rokubacteriales and increased the relative abundances of Bacillus and Skermanella， which resulted in the proportions of exchangeable-Cd （F1-Cd） being reduced by 8.13%-24.54%. Further， the DI treatment increased the relative abundances of Bacillus， unclassified_ f__JG30-KF-CM45， and unclassified_ f__A4b， which enlarged the proportions of specifically adsorbed-As （F2-As） by 9.73%-31.36%. Therefore， the variation of the above-mentioned genera has driven the bio-transformation of Cd and As in soil， and DI decreased Cd concentrations in the soil solution by 73.78% maximally compared with that of FI and further inhibited Cd transport from glume to grain. However， the DI treatment improved the concentrations of As in the soil solution by 171.73% maximally but inhibited As translocation from rachis and glume to grain compared with those in FI and SI， respectively. Additionally， DI alleviated the accumulation rates of Cd and As in wheat grain and finally reduced the concentrations and accumulation of Cd and As in the grains. In summary， drip irrigation is a better pathway to save water resources and reduce Cd and As accumulation in wheat grain cultivated in calcareous soil with moderate Cd and As co-contaminated agricultural land， which could provide a new strategy for the safe utilization of heavy metal-contaminated farmland.