Purpose Farmland soil is heavily polluted by heavy metals. Cadmium pollution not only can affect the rice yield, quality and whole farmland ecosystem function in paddy fields, but also can harm human health through food chain transmission. Fertilization has a significant effect on the bioavailability of heavy metals. Nitrogen fertilizer is as an important stimulation in an agricultural production; therefore, the appropriate amount of fertilizer is vital for the bioavailability of cadmium in the application of nitrogen fertilizer in paddy soils.
Method The effects of nitrogen fertilizer on the migration and transformation of cadmium and the uptake of rice were studied to simulate the concentration of cadmium in paddy field at 5 mg/kg by using different nitrogen application rates: no nitrogen treatment (CK), nitrogen fertilizer application rate of 90 kg/hm2 (CF90), nitrogen fertilizer application rate of 150 kg/hm2 (CF150), nitrogen fertilizer application rate of 200 kg/hm2 (CF200) in pot experiment.
Result The application of nitrogen fertilizer reduced the pH value in soil, and the pH value of high nitrogen treatment decreased from 6.3 to 5.7. High nitrogen application increased the Eh value in rice soil, especially at elrogation stage. The proportion of exchangeable cadmium in the soil decreased from 65% to 50%, but increased the proportion of exchangeable cadmium in the soil, and the proportion increased from 5% to 15%.
Conclusion The amount of nitrogen applied was negatively correlated with pH, and it was positively correlated with the cadmium content of aboveground pant . The high nitrogen application promoted the transfer of cadmium to the aboveground part of rice, and the content of cadmium in the aboveground part of rice was positively correlated with the amount of nitrogen applied in this study. The results provide an important reference for the adoption of agronomic measures to regulate the use of cadmium contaminated farmland.
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