Abstract
Most cadmium-polluted farmland and land surrounding mining areas are difficult to repair and control, seriously threatening the food safety of the crops planted in these regions. As an essential element for plant growth, calcium plays an important role in stress-resistance regulation. In this study, Brassia campestris L. was used as the experimental material and polluted soil with cadmium was used as the experimental soil sample, to explore the competition inhibition of calcium polypeptide application on the absorption of Cd2+ by Brassia campestris L. in the growth process, as well as the effect of calcium application on the growth. Results showed that the application of calcium polypeptides significantly promoted the growth of Brassia campestris L. Calcium polypeptides could be used as high-quality fertilizer, alleviating the effect of Cd2+ stress on the growth of Brassia campestris L., and promoting the absorption of K+, Ca2+, and other nutrients by Brassia campestris L. Under different calcium polypeptide application conditions, the effective state of Cd2+ in the soil showed less significant difference, indicating that the calcium polypeptide had weak or limited passivation effects on Cd2+. There was a significantly negative correlation between Cd concentration in Brassia campestris L. and calcium application (r = −0.99, p < 0.01) when calcium polypeptide was over-applied, which indicates that the inhibition effect of Cd2+ absorption on Brassia campestris L. is mainly through competitive inhibition rather than passivation. The results showed that calcium polypeptide has dual functions on the competitive inhibition of heavy metals and a good fertilizer effect, providing a new technology for in situ remediation of heavy-metal pollution, and a new approach for the treatment of cadmium-contaminated farmland and surrounding mining land.
Highlights
Cadmium (Cd2+ ) is a highly toxic heavy-metal element
In the experimental soil with 2.0 and 5.0 mg·kg−1 cadmium, six different calcium application gradients were set to apply calcium polypeptide, and the same nitrogen application amount was gradients were set to apply calcium polypeptide, and the same nitrogen application amount was supplemented with urea according to the optimum nitrogen application amount of Brassia campestris L., supplemented with urea according to the optimum nitrogen application amount of Brassia campestris
Results showed that the application of water-soluble calcium polypeptide could promote the growth of Brassia campestris L., increase its fresh weight and chlorophyll a content, turn significantly promote the growth of Brassia campestris L., increase its fresh weight and chlorophyll a its leaves green, and improve its quality in medium-concentration cadmium-polluted soil; in the content, turn its leaves green, and improve its quality in medium-concentration cadmium-polluted polluted soil with 2.0 mg·kg−1 cadmium,−1the heavy-metal cadmium would have a toxic effect on the soil; in the polluted soil with 2.0 mg·kg cadmium, the heavy-metal cadmium would have a toxic production of Brassia campestris L. [11,15], and reduce its growth to a certain degree
Summary
Cadmium (Cd2+ ) is a highly toxic heavy-metal element. Soil pollution from heavy metals has become increasingly serious, especially in farming soil. The area of cultivated land polluted by heavy metals in China is about 10 million hectares, accounting for more than 8% of the total cultivated-land area. Soil Pollution Survey Bulletin issued in 2014, inorganic pollution was the main type, for which Cd exceeded the standard by 7%, which was much higher than that for other heavy metals. Most cadmium-polluted agricultural land and regions surrounding mining areas in China are still planting bases with large areas and are very difficult to remediate, which seriously threatens the food
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