The objective of this research was to study the differences in the enrichment and transport capacity of heavy metal chromium in farmland soil by different maize cultivars, and it is of great significance to screen out the maize varieties that meet the food safety standards and repair the heavy metal chromium in farmland soil. To complete the experiment, under the conditions of field experiments, 72 maize cultivars were selected to study the growth of maize in chromium-polluted arable land and the differences in Cr accumulation and transshipment of different maize cultivars. From the experiment, we found that among 72 maize varieties, 49 of them, accounting for 68.06% of the total, had kernel chromium content lower than the China kernel limit standard value of 1.0 mg kg−1. There were significant differences in Cr content in the kernels, stems, leaves and roots of all cultivars, with Cr content in root > stems > kernels. The contents of Cr in roots and stems and kernels were 4.06–93.09 mg kg−1 and 5.54–24.13 mg kg−1 and 0.46–2.61 mg kg−1, respectively, and the coefficients of variation were 51.21%, 36.36% and 46.11%. By cluster analysis, maize varieties were divided into five groups according to kernel chromium content, and the maize varieties were also divided into three categories according to the content of chromium in stem and leaf. At the same time, we found that the low accumulation of kernel, high accumulation of stem and leaf, seven varieties: Nongyu662, HongyuNO.9, Wankenyu125, Shuxinyu228, Kewei702, Liyu16, JinchengNo.6. The enrichment coefficients (BCF) of each maize cultivar ranged from 0.026 to 0.194, the transport coefficients TF (kernel/stem) and TF (stem/root) were between 0.028 and 0.064, and 0.064 and 0.864, and the enrichment coefficient and transport coefficient were less than 1. In the end, according to the comprehensive evaluation of the maize growth status, kernel Cr content, enrichment coefficient, transport coefficient and other indicators, it is believed that Nongyu662, HongyuNo.9, Wankenyu125, ShuXinYu228, Weike702, Liyu16, and JinchengNo.6 could be promoted as Cr maize cultivars with low kernel and high stem–leaf accumulation; also, planting these seven varieties can achieve the goal of restoring the heavy metal chromium in farmland soil while ensuring maize food security.

The effect of various soil amendments on cadmium (Cd)-contaminated farmland was evaluated in terms of effectiveness, safety, economics, and simplicity. Experiments were conducted in May 2020, on Cd-contaminated land in Tong Ling, An Hui, China. The efficacy of optimized fertilization and heavy metal passivators—gypsum, bamboo charcoal, lime, and a compound passivator (mixture of bamboo charcoal, silicon fertilizer, gypsum, furfural residue, plant ash, and chicken manure)—was evaluated as amendments to reduce the uptake of Cd in rice. The results indicate that all treatments reduced the Cd bioavailability in Cd-contaminated soil and rice grain Cd accumulation to levels that meet national food safety standards. Moreover, the rice yield increased by 4.80 to 14.27% and the Cd content in rice grains decreased by 23.53 to 36.83%. The efficacy of Cd reduction in rice was as follows: optimized fertilization > lime > compound passivator > bamboo charcoal > gypsum powder. Wheat was planted after the rice season to test the effect of the soil amendment measures implemented during the rice season on crop growth in the next season. Wheat yield improved by 3.46 to 10.96%, and the grain Cd content decreased by 6.47 to 41.03%. The efficacy of Cd reduction in wheat was as follows: lime > compound passivator > optimized fertilization > gypsum powder > bamboo charcoal. Following the lime treatment, the wheat grain Cd content met national food safety standards. A comprehensive comparison was conducted to evaluate the safe utilization and economic effect of the passivator and optimized fertilization. The results reveal that optimized fertilization was the most effective treatment. The findings from this study provide a scientific basis for safe rice–wheat rotation systems on mildly Cd-contained farmland (0.3 mg/kg < Cd < 1.0 mg/kg) in the Yangtze River Basin.

Using agronomic measures to remediate heavy metals on farmland is the main measure to achieve the safe utilization of crops. Investigating the effects of applying different fertilizers on the uptake, and translocation of Chromium (Cr) in maize and on the effectiveness of Cr in soil under Cr contamination of farmland is of great theoretical and practical significance to achieve the safe utilization of arable land and safe production of agricultural products. Under field trial conditions, different fertilizer types were set up, including ammonium sulfite, calcium-magnesium phosphate, and diammonium phosphate. locally formulated fertilizers (urea-ammonium phosphate-potassium chloride) serving as the control, with Biochar and conditioner PX5B were chosen to compare the impacts of each. To study the effects of different fertilizer types on maize yield, Cr content in the plant, bioconcentration factor, translocation factor and available content of Cr in the soil. The results showed that Compared with the formulated fertilizer, all treatments could improve pH, soil organic matter (SOM） and reduce the effective state of Cr content in the soil by 15.05% to 42.66%. While the Cr content of maize grains treated with biochar and conditioner PX5B was 0.80 mg·kg-1 and 0.88 mg·kg-1 with reduction rates of 39.95% and 33.83%, respectively. The Cr content of maize grains treated with various fertilizer treatments ranged from 0.82 to 1.32 mg·kg-1 with reduction rates of 0.75% to 38.19%. The Cr content of maize grains could be brought down to below the national food safety standards of China(1.0 mg·kg-1) using urea – calcium magnesium phosphate - potassium chloride, urea - diammonium phosphate - potassium chloride, ammonium sulfite – calcium magnesium phosphate - potassium chloride and ammonium sulfite, urea – calcium magnesium phosphate - potassium chloride and the two conditioner treatments. Among the different fertilizer treatments, the best fertilizer treatment for reducing the effective state Cr content of soil and the Cr content of maize grains was ammonium sulfite-calcium-magnesium-phosphate fertilizer-potassium chloride, which could achieve similar reductions as the two conditioners, while it also had a certain reduction effect on the Cr content in maize roots and straws and on the aboveground bioconcentration factor（BCF） and the root-to-straw translocation factor（PTF） of maize for Cr. Therefore, the combination of ammonium sulfite and calcium magnesium phosphate is the best fertilizer combination to block the absorption of Cr by maize and has some implications for the fertilization of farmland under acidic soil conditions of Cr contamination.

Screening for low-accumulation varieties is an effective way to reduce the cadmium (Cd) content in crops and decrease human Cd intake. In this study, a field experiment was conducted to analyze the characteristics of Cd absorption and accumulation in 24 maize varieties at maturity in farmland with different levels of Cd pollution. Cluster analysis and Pareto analysis methods were used to screen for maize varieties with low Cd absorption. In addition, the environmental threshold of Cd in farmland in the study area was estimated based on the Species Sensitivity Distribution (SSD) characteristics of different maize Cd enrichment coefficients (1/BCF). The results showed that maize in the study area was subject to varying degrees of Cd pollution, with total soil Cd content ranging from 1.81 to 2.71 mg·kg−1 at test site 1 and from 0.95 to 1.76 mg·kg−1 at test site 2. Only the Cd content of heavy metals in maize kernels at test site 2 did not exceed China’s national food safety standard (GB 2762-2022, 0.1 mg·kg−1), with the Cd content of different maize varieties at test site 2 ranging from 0.008 to 0.073 mg·kg−1 and the bioconcentration factor (BCF) of maize kernels for Cd ranging from 0.004 to 0.054. According to cluster analysis and Pareto analysis, the low-Cd accumulation maize varieties suitable for local planting were identified as Yufeng 303, Nongda 372, Jingnongke 728, MC121 (Fengda Seed Industry), and Jinyu 1233. In addition, the soil Cd environmental threshold for ensuring that 95% of maize would not be polluted by Cd in soil was derived as 1.39 mg·kg−1.