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.

Plant extraction is a thorough remediation method to remove heavy metals from soil. Chelating agents can enhance the extraction effect of heavy metals from soil by plants. In this study, low molecular weight organic acids (LMWOAs), such as citric acid (CA), tartaric acid (TA) and polyaspartate (PASP), were added to the farmland soil contaminated with Cd and Pb and combined with corn to enhance the absorption and extraction of Cadmium (Cd) and Plumbum (Pb). The effects of LMWOAs on the growth and yield of maize, Cd and Pb concentrations in each part of maize, rhizosphere soil pH, total cadmium and lead content and DTPA-Cd and Pb concentrations were studied. The enrichment, transport and extraction ability of maize were analyzed, and calcium chloride (CaCl₂) was compared. The results showed that: (1) Exogenous LMWOAs increased the biomass and yield of maize compared with no material added (CK), and CA increased the yield of maize by 6.33%. (2) Exogenous LMWOAs promoted the uptake of Cd and Pb in all parts of maize, and the distribution of Cd and Pb in all organs was as follows: straws > roots > maize cobs > kernels and roots > straws > maize cobs > kernels. The Cd and Pb concentrations in maize kernels were in line with GB 13078-2017 in China, which could be used as feed maize. (3) Exogenous LMWOAs enhanced the enrichment of Cd and Pb in maize straws and roots. PASP had a good enrichment effect on Cd and Pb. CA and CaCl₂ could enhance the transport capacity of Cd and Pb from maize roots to straw. (4) Compared with CK, the total amount of Cd and Pb in rhizosphere soil decreased by 6.93–26.99% and 2.74–6.79%, respectively. LMWOAs could promote the concentration of DTPA-Cd and Pb in rhizosphere soil, and PASP had the most significant increase in DTPA-Cd and Pb in rhizosphere soil. Compared with CK, the soil pH value decreased by 0.03–0.14 units. LMWOAs can enhance the removal of heavy metals from maize, and PASP has the most significant comprehensive effect.

Using agronomic measures to remediate heavy metal chromium (Cr) on farmland is the main measure to achieve the safe utilization of crops. This study was conducted under field trial conditions using locally formulated fertilizers (urea–ammonium phosphate–potassium chloride) as the control. Different fertilizer-type treatments such as ammonium sulfite, calcium magnesium phosphate, and diammonium phosphate were set up. Biochar and soil conditioner PX5B were chosen to compare the impacts of each to study the effects of different fertilizer types on maize yield, Cr content in each part, the bioconcentration factor, the translocation factor, and the available content of Cr in the soil. The results show that, compared with the formulated fertilizer, all treatments improved pH and soil organic matter and reduced the effective state of Cr content in the soil by 15.05% to 42.66%. The Cr content of maize grains under biochar and soil conditioner PX5B treatments were 0.80 mg·kg⁻¹ and 0.88 mg·kg⁻¹ with a 39.95% and 33.83% reduction, respectively, whereas the Cr content of maize grains under various fertilizer treatments was in the range of 0.82~1.32 mg·kg⁻¹ with a 0.75%~38.19% reduction, respectively. Among the different fertilizer treatments, urea–calcium magnesium phosphate–potassium chloride, urea–diammonium phosphate–potassium chloride, ammonium sulfite–calcium magnesium phosphate–potassium chloride, and ammonium sulfite and urea–calcium magnesium phosphate–potassium chloride treatments reduced the Cr content of maize grains to within the range of the national food safety standard of China (1.0 mg·kg⁻¹). The best reductions in the effective state Cr content of the soil and the Cr content of maize grains were achieved by ammonium sulfite–calcium magnesium phosphate–potassium chloride treatment, which was able to achieve similar reductions to the two conditioners. It also had a reduction effect on the Cr content of maize roots and straws, the aboveground bioconcentration factor (BCF), and the primary translocation factor (PTF). 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.

Effective, economical and feasible remediation technology of heavy metal pollution in farmland is an important research concentration in the field of farmland soil remediation. In order to investigate the remediation effects of formula fertilizer and biochar on cadmium (Cd)–plumbum (Pb) contaminated farmland, blank (CK), lime (SH), biochar (SWT), formula fertilizer (FL), and biochar + formula fertilizer (FS) were set up in Cd–Pb contaminated farmland. The results demonstrated the following: (1) Compared with CK, SWT and FS increased the yield by 11.21% and 15.00%, respectively, which was significantly higher than other treatments. (2) The concentrations of Cd and Pb in maize kernels under all treatments were lower than the limited value stipulated by GB 2762-2022 in China. Compared with CK, FS reduced the concentration of Cd and Pb in maize kernels by 24.96% and 31.46%, respectively, which were the most significant. All the treatments can reduce the concentrations of Cd and Pb in maize cob and straw and inhibit the transfer of Cd and Pb from the lower part of the maize field to the overground part. (3) FL, SWT, and FS increased soil pH by 0.17, 0.10, and 0.19 units, respectively. FS can reduce the concentrations of available cadmium (DTPA-Cd) and available lead (DTPA-Pb) significantly, which are 31.05% and 38.57% lower than CK, respectively. (4) Each treatment can reduce the extraction state and reducible state of weak acid Cd and Pb in soil, while increasing the proportion of oxidizable state and residual state. FL and FS significantly increased the percentage of residual Cd and Pb by 18.00% and 24.32%, respectively, and 33.33% and 37.76%, respectively. (5) FL (1.747) and FS (1.679) were relatively higher than CK in input/output. In conclusion, the combined application of biochar and formula fertilizer in Cd/Pb polluted farmland can effectively reduce the concentration of Cd and Pb in maize and has high economic benefits and practicability.

Accurate soil management has long been the focus of research in agroecology. Crop productivity can be enhanced while reducing environmental threats from excessive fertilization by fully comprehending the spatial variability of soil properties and delineating management zones (MZs). A field investigation was carried out at experimental sites outside Hefei City’s administrative districts in China to study the spatial variability of soil properties and the delineation of MZs. A total of 9601 soil samples were collected in the study area. A variety of soil properties were analyzed, including the pH, organic matter, total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus, available potassium, slowly released potassium, available sulfur, available boron, available copper, available zinc, available iron, and available manganese. The coefficient of variation for various soil properties exhibited a wide range, spanning from 12.2% to 100.5%. The geostatistical results show that most soil properties have moderate to strong spatial autocorrelation, and the ordinary kriging method is used to map the distribution of soil properties. The principal component analysis method was used to reduce the dimension of 13 soil properties to 4 principal components, and the fuzzy c-means clustering method was used to delineate MZs. The calculation results of the fuzzy performance index and normalized classification entropy show that the optimum number of MZs is five. In the study area, the western part exhibits the highest soil fertility, primarily attributed to its elevated organic matter content. Additionally, organic matter emerges as a key factor influencing sustainable agricultural production in this region. These results form the basis for soil managing areas outside the administrative districts of Hefei City.

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.