Effects of Fertilizers and Conditioners on Chromium Uptake of Maize in Chromium-Polluted Farmland

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.