China is vigorously promoting green, environmentally friendly, and sustainable agricultural practices, with a strong emphasis on the efficient recycling of biomass resources. In particular, in the field of fertilizer use, the country has clearly stated the need to reduce the application of chemical fertilizers, improve fertilizer use efficiency, and promote the substitution of chemical fertilizers with organic fertilizers. This study aims to explore the effects of different application rates of biochar-based organic fertilizers on soil-available nutrients, corn growth, and the inhibition of cadmium absorption and transfer in corn through field experiments. The experiment consisted of 10 treatments, including a blank control (CK), organic fertilizer at 1500 kg/ha (T1), 3000 kg/ha (T2), and 4500 kg/ha (T3), biochar-based organic fertilizer I at 1500 kg/ha (T4), 3000 kg/ha (T5), and 4500 kg/ha (T6), and biochar-based organic fertilizer II at 1500 kg/ha (T7), 3000 kg/ha (T8), and 4500 kg/ha (T9). The results indicate that the surface of the modified biochar exhibited significant fracturing and breakage, with an increase in pore size and pore number. Mn elements were successfully loaded onto the surface of the biochar, and the number of certain original functional groups was increased. Among all treatments, the T9 treatment (biochar-based organic fertilizer II at 4500 kg/ha) showed the best results in improving soil pH, organic matter, alkali-hydrolyzable nitrogen, and available potassium, significantly increasing these parameters by 0.69 units, 19.01%, 22.20%, and 36.24%, respectively, compared to the control. The T8 treatment (biochar-based organic fertilizer II at 3000 kg/ha) showed the best effect in reducing soil-available cadmium and cadmium content in corn grains, with reductions of 32.84% and 26.28%, respectively, compared to CK. The T9 treatment also had the most significant effect on increasing corn yield, plant height, crown width, and leaf length, with improvements of 64.08%, 0.16 m, 21.05%, and 9.28%, respectively, compared to CK. Correlation analysis revealed that corn yield, plant height, crown width, and leaf length were significantly positively correlated with soil pH, organic matter, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium, while they were significantly negatively correlated with soil-available cadmium content. In summary, the application of organic fertilizers and biochar-based organic fertilizers I and II can improve soil pH, organic matter, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium in cadmium-contaminated soils while also significantly enhancing corn yield and growth traits. Moreover, these fertilizers effectively reduce available cadmium in the soil and cadmium content in corn grains. Among the treatments, biochar-based organic fertilizer II performed the best in promoting crop growth, enhancing soil nutrient content, and reducing both soil-available cadmium and corn grain cadmium content, with the effectiveness ranking as follows: biochar-based organic fertilizer II > biochar-based organic fertilizer I > organic fertilizer. The results of this study provide a new approach to the resource utilization of agricultural waste and offer a theoretical basis for safe crop production in the context of heavy metal pollution.

Chinese cabbage (Brassica pekinensis (Lour.) Rupr.) is rich in many vitamins and many minerals and is an important green vegetable in people’s daily diet. Soil heavy metal Cd content exceeding safe values has a toxic effect on the growth of vegetables, which seriously affects human health. Biochar can effectively stabilize heavy metals in polluted soil, and phosphogypsum can improve the physical and chemical properties of soil and promote the growth of crops. To explore the remediation effect of biochar combined with different amounts of phosphogypsum on Cd-contaminated soil and the safe production of agricultural products, a pot experiment was conducted with corn straw biochar and harmless phosphogypsum as the test materials, and Chinese cabbage as the test plant. The soil pH; the alkali-hydrolyzed nitrogen content; the available phosphorus, potassium, and Cd content in the soil; the fresh weight of the Chinese cabbage; the Cd content in the edible part of the Chinese cabbage; and the vitamin C, chlorophyll, and soluble sugar contents in the leaves were measured and analyzed. The results showed that among all the treatments, the T3 and T4 treatments were the most effective in enhancing the soil pH and soil available nutrient content. Compared with CK, the T3 and T4 treatments significantly enhanced the soil pH by 0.27 and 0.29 units, respectively, and significantly increased alkali-hydrolyzed nitrogen content by 16.25% and 14.04%, available phosphorus content by 22.98% and 22.87%; and available potassium content by 8.50% and 10.13%. In addition, among all the treatments, the T3 treatment had the best effect on reducing the soil available Cd content and the Cd content in the edible part of the Chinese cabbage, which were significantly reduced by 17.05% and 49.35%, respectively, compared with CK, and the T3 treatment had the best effect on improving the yield and quality of the Chinese cabbage, significantly increasing the fresh weight of the Chinese cabbage by 31.86%, the soluble sugar level by 9.54%, the vitamin C level by 15.38%, and the chlorophyll level by 13.28%, compared with CK. In summary, 3000 kg/hm² of biochar combined with 3000 kg/hm² of phosphogypsum can significantly reduce the effectiveness of soil Cd, prevent the transfer of Cd to Chinese cabbage, reduce the ecological risk of Cd, and improve the yield and quality of Chinese cabbage. The results provide a theoretical basis for the safe production of agricultural products in Cd-contaminated soil and promote the recycling of resources for the benefit of the environment.

In this paper, different materials such as phosphogypsum, raw coal and iron slag, which are more concerned in chemical passivation, are selected to mix an efficient and cheap passivation agent to repair Cd and As compound contaminated soil and realize the reuse of solid waste resources. The heavy metals Cd and As are not only toxic to the soil-plant system, but also migrate to animals and humans through the food chain, destroying normal physiological functions, and causing great harm to the human body. The essential functions of the newly developed heavy metal passivator are as follows: • Changed the microscopic morphology of the soil • Greatly reduce the bioavailability of Cd and As in the soil

The southwestern region of China is one of the major maize (Zea mays L.)-producing areas and a concentrated zone of farmland contaminated by heavy metals (HMs). Selection of maize varieties with low accumulation of HMs under complex HM pollution conditions is one the most feasible and effective ways for safe utilization of HM-polluted farmland. In this study, we conducted field experiments to investigate the differences in biological traits among 28 local maize varieties under combined soil pollution with Cd, Pb, As, Cr, and Hg. We analyzed the absorption, accumulation, and transport characteristics of Cd, Pb, As, and Cr in various parts of the maize plant (Hg was not detected in any part of maize plants) and explored the relationships of HM contents in different parts of maize with soil HM contents through cluster analysis, correlation analysis, and principal component analysis. The results indicated that among different biological traits of maize, root length, root dry weight, and plant height were the most significantly influenced by soil HM content, while stem dry weight was the least affected. The accumulation capacity of various maize parts for HMs followed the order of grains < stems < cobs < leaves < roots, while the transport capacity followed the order of root–grain < root–stem < cob–grain < stem–cob < stem–leaf. In addition, the accumulation capacity of maize grains for HMs followed the order of As < Cr < Pb < Cd. Different HMs exhibited synergistic effects in various maize parts, except for the stem, particularly in the grains. A synchronous transport mechanism was observed for As and other HMs in different parts. The accumulation of HMs in maize was primarily derived from human activities such as the extraction, storage, and smelting of non-ferrous metals, while the HMs in soil parent material and weathering products played a secondary role. The yield of the tested maize varieties ranged from 7377.6 to 11,037.0 kg·hm⁻², with M5 (Haoyu 1511) achieving the highest yield. M2, M4, M5, M9, M10, M21, and M25–28 were identified as suitable varieties with low Cd, Pb, As, and Cr accumulation for popularization in HM-contaminated soils in southwestern China due to their low accumulation of HMs.

To explore strategies for the safe utilization of farmland co-contaminated with cadmium (Cd) and lead (Pb), this field study systematically evaluated the impacts of humic acid (HA) and potassium fulvate (PF) at different application rates (0, 1500, 3000, and 4500 kg·ha⁻¹) on the growth, yield, and translocation of Cd and Pb within the soil–plant system of maize (Zea mays L.). The results showed that while HA and PF did not significantly alter total soil Cd and Pb concentrations, they markedly reduced their bioavailable fractions. This mitigation of heavy metal phytotoxicity significantly promoted maize growth and yield, with the high-dose HA treatment increasing yield by a maximum of 32.9%. Both amendments dose-dependently decreased Cd and Pb concentrations, bioconcentration factors (BCF), and translocation factors (TF) in all maize tissues, particularly in the grains. At equivalent application rates, PF was slightly more effective than HA in reducing heavy metal concentrations in the grains. Notably, a significant positive correlation was observed between Cd and Pb concentrations across all plant parts, confirming a synergistic accumulation and translocation mechanism. This synergy provides a physiological explanation for the broad-spectrum immobilization efficacy of these humic substances. In conclusion, applying HA and PF presents a dual-benefit strategy for increasing yield and reducing risks in Cd- and Pb-contaminated farmlands. This study proposes a differentiated application approach: PF is the preferred option when ensuring food-grade safety is the primary goal, whereas high-dose HA is more advantageous for maximizing yield in soils with low-to-moderate contamination risk.