Impacts of In Situ Wheat Straw Incorporation Methods on Cadmium Behavior in Soil-Rice Systems

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Cadmium (Cd) contamination in paddy soils is a significant food safety concern.
• Straw incorporation is a sustainable agriculture practice, but its mechanisms for regulating Cd in rice are not fully understood.

Purpose of the Study:

• To investigate the effects of different wheat straw management practices on cadmium availability and rice safety.
• To evaluate the role of straw-derived biochar in mitigating cadmium accumulation in rice.

Main Methods:

• Field study at two Cd-contaminated sites using two rice cultivars (low-Cd ZLY8612, high-Cd YXY2115).
• Evaluated five wheat straw management practices: straw removal (CK), straw mulching (SM), straw incorporation (SI), straw incorporation with organic fertilizer (SOI), and straw-derived biochar incorporation (SBI).
• Assessed Cd availability, transformation to residual fractions, soil microbial community structure, and grain Cd concentration.

Main Results:

• Straw incorporation with organic fertilizer (SOI) and straw-derived biochar incorporation (SBI) reduced Cd availability and promoted its transformation to residual fractions.
• SBI demonstrated superior Cd immobilization effects and enriched beneficial soil bacteria (Bacillus, Sphingomonas, Flavisolibacter), increasing Proteobacteria while decreasing Chloroflexi and Acidobacteriota.
• All treatments increased rice yield, but only SBI significantly reduced grain Cd in the high-Cd cultivar to below the 0.2 mg/kg threshold in high-Cd soil.

Conclusions:

• Straw-derived biochar incorporation (SBI) is a highly effective strategy for immobilizing cadmium in paddy soils.
• Combining SBI with low-Cd accumulating rice cultivars offers a reliable agronomic approach for safe grain production.
• This integrated strategy supports sustainable straw recycling in Cd-contaminated rice-wheat rotation systems.