Understanding the role of pig manure, rice straw, and calcium carbonate on the cadmium pollution in soil–wheat system

Abstract

To explore the specific effects of pig manure and rice straw on cadmium-contaminated soils and the effect of different mass fractions of calcium carbonate on cadmium efficacy, a pot experiment was conducted with different rates of pig manure, rice straw, and calcium carbonate. The results showed that pig manure addition increased the soil humic acid/fulvic acid ratio, thereby reducing the available Cd. The addition of calcium carbonate increased the soil pH and reduced the available Cd. The addition of pig manure and calcium carbonate significantly reduced the Cd content of wheat grains by 51.96% and 45.95%, respectively, at 3% and 5% application rates. Rice straw application reduced the soil pH, improved the soil Cd availability, and increased the accumulation of Cd in wheat grains. Compared with that in the control, the grain biomass increased significantly with 3% pig manure and 3% rice straw application, and the grain biomass increased significantly, by 58.86% and 39.11%, and 93.3% and 75.08%, respectively, in 2020 and 2021. With the application of calcium carbonate, the grain biomass of wheat first decreased and then increased. Additionally, the grain biomass significantly increased by 26.36% and 71.22%, respectively, at the 5% calcium carbonate application rate. Therefore, high application rates of pig manure (3% and 5%) have potential application in the safe production of wheat in Cd-contaminated soils.