Effects of foliar dressing of selenite and silicate alone or combined with different soil ameliorants on the accumulation of As and Cd and antioxidant system in Brassica campestris

- All treatments showed limited effects on the fresh leaf biomass of B. campestris.
- Soil addition of CMP, SS and RM could inhibit the uptake of As and Cd in the leaves.
- Foliar spraying of Se or Si could help CMP reduce the leaf contents of As and Cd.
- Foliar spraying of Se or Si failed to help RM reduce the leaf contents of As and Cd.
- CMP2Se2 is an optimal choice to control As and Cd content and trigger enzyme activity.

This study was conducted to investigate the possibility of using a combined technology to synchronously reduce As and Cd accumulation in the edible parts of Brassica campestris. The results showed that a foliar application of selenite (Se) and silicon (Si) combined with soil ameliorants (including Ca-Mg-P fertilizer, sodium silicate and red mud) showed limited effects on the growth of B. campestris. The As concentration in the leaves of B. campestris in all treatments was below the Chinese safety standard. When sodium silicate and Ca-Mg-P fertilizer were added to the soil, the additional foliar application of Se and Si could in some cases help further reduce the concentrations of As and Cd in the leaves of B. campestris. However, when red mud was applied to the soil, the foliar application of Se and Si enhanced the Cd concentration in the leaves of B. campestris. In most cases, high levels of soil ameliorants plus foliar application of Se and Si significantly enhanced the As concentrations in both the soil solution and the roots of B. campestris but reduced the soil solution Cd concentration and the leaf As concentration. Most of the treatments reduced the thiobarbituric acid reactive substances (TBARS) concentration in the leaves of B. campestris, and the foliar application of Se and Si helped the soil ameliorants alleviate the oxidative stress resulting from As and Cd exposure. In this study, several treatments significantly increased the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX). However, the enzymes peroxidase (POD) and catalase (CAT) were not induced by most treatments. In summary, the combined treatment of 1 g kg−1 Ca-Mg-P fertilizer plus foliar spraying 2 mmol L−1 sodium selenite was most effective in reducing the Cd concentration and a rather strong ability to reduce the As concentration and trigger the activities of SOD and APX in the leaves of B. campestris.