Search

Organic fertilizers may contain cadmium (Cd) and the transformation of organic materials in soil also has a role in soil-plant Cd distribution, both of which lead to Cd accumulation in plant edible parts. However, the advisability of applying organic fertilizer to remediate soils that are moderately and slightly contaminated with Cd has not been clarified. In this study, we investigated the impacts of an organic amendment (chicken manure) on the Cd concentration in rice grains (Cd R ) and the soil chemical properties over a five year period (10 rice seasons) within a slightly contaminated paddy soil in Hunan Province, subtropical China. We found that the Cd R was reduced by 28%-56% as a result of the organic amendment. The within-year reduction in Cd R was higher in late rice (43%-56%, averaging 51%) than in early rice (28%-45%, averaging 38%); however, the inter-annual reduction in Cd R was fairly stable (40%-49%), which suggests that chicken manure amendment has a long-term and persistent remediation potential. The concentrations of DTPA-extractable Cd and exchangeable plus water-soluble Cd fractions in soil were reduced, whereas soil pH and the concentrations of soil organic C and its labile fractions increased. These results indicate a lower apparent phytoavailability of Cd in soil following organic amendment. A two-variable empirical model using DTPA-Cd extracted from the soil at the full heading stage of rice and a climatic factor (total precipitation during the rice growing season) showed great potential in effectively predicting Cd R . Our study suggests that Cd phytoavailability in soil (indexed by DTPA-extractable and exchangeable Cd) and climatic factors (such as temperature and precipitation) may control inter-annual reductions in Cd R following organic amendment in slightly contaminated paddy soils., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Background and aims: Liming is widely known as a cost-efficient agricultural practice to reduce cadmium (Cd) concentration in rice (Oryza sativa L.) grain (CdR) in the short term. However, the effect of long-term continuous liming on CdR-reduction in the context of other environmental controls remains unknown. Methods: We quantified the temporal stability of CdR-reduction in response to biannually continuous liming and its correlations with dynamic soil properties and weather conditions based on a 7-year field experiment in a subtropical double-cropping rice ecosystem in a moderately Cd-contaminated acidic soil. Results: The CdR value declined by 51–90% with liming without compromising the rice yield. The degree of CdR-reduction was similar between early and late rice seasons. However, the between-year CdR-reduction was variable, remaining relatively stable in the first three years and fluctuating in the last four years. Soil pH and Olsen-P concentration at the ripening stage rose significantly, while the concentrations of diethylenetriaminepentaacetic acid (DTPA)-extractable Cd, Mn, and Zn in soil remained unaffected. The soil pH did not further increase after the second year of liming. The soil pH and Olsen-P concentration were positively correlated with cumulative liming, but the CdR and CdR-reduction exhibited no correlations with cumulative liming. The CdR was correlated negatively with precipitation but positively with temperature and sunshine duration. Conclusions: The effect of 7-year continuous liming on CdR-reduction was temporally unstable and had no significant cumulative effect on CdR. The between-year CdR-reduction was not controlled by accumulative liming but primarily by dynamic soil properties and weather conditions. [ABSTRACT FROM AUTHOR]