Tillage practices alter the interaction between soil and rice straw, impacting soil quality and cadmium (Cd) dynamics. However, the effects of tillage and straw management strategies on soil Cd accumulation and rice uptake remain unclear. This study investigated how tillage and straw practices influence rice Cd uptake by altering soil Cd mobility and bioavailability. A long-term field experiment was conducted with four treatments: no-tillage with straw return on the soil surface (NTS), rotary tillage with straw incorporation (RTS), plow tillage with straw incorporation (PTS), and plow tillage with straw removed (PT). Results showed that Cd concentrations in rice organs (root, stem, leaf, and rice grain) decreased in the order NTS>RTS>PTS, with only PTS maintaining grain Cd levels below 0.2 mg kg^–1. Compared with NTS and RTS, the average Cd concentrations in rice grain under PTS were significantly reduced by 56.76 and 25.88%, respectively. A partial least squares path model indicated that reductions in available Cd (Avail-Cd) and acid-soluble Cd (Aci-Cd), combined with iron plaque (IP) formation on the roots, were key factors in lowering rice Cd levels. PTS reduced Avail-Cd and Aci-Cd by decreasing soil bulk density, increasing soil organic matter, pH, and the abundances of Nitrospirota and Bacteroidota. Moreover, PTS enhanced soil nutrient and Fe²⁺ levels, promoted IP formation on rice roots through improved root morphology and antioxidant activity, and limited Cd uptake. Although PTS increased total and available soil Cd compared to PT, its promotion of IP formation mitigated rice Cd uptake, resulting in comparable grain Cd concentrations between the two. Thus, long-term plow tillage with straw incorporation emerges as a sustainable practice to enhance soil quality and reduce Cd uptake in the rice cropping system.

Cadmium (Cd) uptake by rice plants and its subsequent movement through food chains pose a notable risk to the health of both plants and humans. Therefore, understanding the fundamental mechanisms underlying the uptake and movement process is essential. Through transcriptome analysis, we found that numerous abscisic acid (ABA)-related genes responded to Cd stress. Exogenous application of ABA significantly reduced Cd accumulation in the shoots and roots of rice plants. The increased ascorbate peroxidase (APX) enzyme activity, decreased H₂O₂ content, and elevated Cd tolerance index collectively suggest that ABA may mitigate the toxicity of Cd in rice plants. Further study revealed that exogenous ABA reduced Cd accumulation by regulating Cd transport and cell wall sequestration. Consistently, mutation of the ABA signaling factor OsABI5 resulted in a significant increase in Cd accumulation in shoots. Moreover, foliar spraying of ABA during the grain-filling stage significantly reduced Cd accumulation in rice grains, which was attributed mainly to decreased Cd uptake and the inhibition of Cd transportation from roots to shoots and from leaves to grains. These findings elucidate the underlying mechanisms of the ABA-mediated response to Cd stress in rice and provide a practical reference for coping with Cd pollution in farmlands.