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| Effects of long-term fertilization on heavy metals accumulation and bioavailability in sloping cropland of red soil |
| Received:July 13, 2024 |
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| KeyWord:eroded sloping cropland;red soil;long-term fertilization;pig manure;heavy metal;bioavailability |
| Author Name | Affiliation | E-mail | | LI Jiaqi | College of Land Resources and Environment, Jiangxi Agriculture University, Nanchang 330045, China
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China | | | GUO Zichun | State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China | zcguo@issas.ac.cn | | WANG Yaji | State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China | | | GAO Lei | State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China | | | PENG Xinhua | College of Land Resources and Environment, Jiangxi Agriculture University, Nanchang 330045, China
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China
State Key Laboratory of Efficient Utilization of Arable Land in China, Institute of Agricultural Resources and Regional Planning, CAAS, Beijing 100081, China | pengxinhua@caas.cn |
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| Abstract: |
| In order to investigate the long-term effects of pig manure and chemical fertilizers on the accumulation and bioavailability of heavy metals in eroded red soil sloping fields, a long-term erosion plot experiment（2012—2023）was conducted at the Red Soil Ecological Experiment Station of the Chinese Academy of Sciences. Soil samples were collected from the topsoil layer（0-20 cm）in different years （2012, 2015, 2018, 2020, and 2023）and from the vertical profile（1 m depth）in 2023. The changes in soil pH, soil organic carbon（SOC）, and the total and bioavailable contents of four heavy metals（Cr, Cu, Zn, Cd）were analyzed under three treatments regimes over a 12-year period：no fertilizer application（CK）, chemical fertilizer alone（NPK）, and combined application of pig manure and chemical fertilizer （NPK+PM）. The results showed that, compared to the initial soil conditions, the NPK treatment reduced topsoil pH by 0.2 units to 0.6 units and decreased SOC content by 1.0 g·kg-1 to 1.9 g·kg-1. In contrast, the NPK+PM treatment increased topsoil pH by 0.2 units to 0.6 units and raised SOC content by 0.1 g·kg-1 to 3.0 g·kg-1. Relative to the CK treatment, the NPK treatment significantly increased the available Cr content in the topsoil by 446.2% to 851.2%（P<0.05）. The NPK+PM treatment significantly increased the total Cu and Zn content in the topsoil by 76.3% to 129.6% and 71.2% to 125.8%（P<0.05）, respectively, and significantly raised the available Cr, Cu, and Zn content in the topsoil by 335.0% to 1 213.4%, 162.3% to 1 373.2%, and 275.8% to 2 457.0%（P<0.05）, respectively. By 2023, the total Cu content in the soil reached 56.8 mg·kg-1, exceeding the risk control screening value for agricultural land（50.0 mg·kg-1）. Furthermore, the NPK+PM treatment significantly increased the bioavailability of Cu and Zn in the subsoil（20-100 cm）by 53.9% to 354.2% and 66.3% to 368.2%, respectively（P<0.05）. Correlation analysis showed that under the NPK treatment, the effective states of Cr, Cu, Zn, and Cd, as well as the total Cd content in the soil, were highly significantly positively correlated with soil pH and SOC content（P<0.01）. Under the NPK+PM treatment, the effective states and total amounts of Cu, Zn, and Cd, as well as the effective state of Cr, were highly significantly positively correlated with soil pH and SOC content（P<0.01）.The study concluded that applying chemical fertilizer alone to eroded red soil sloping fields can lead to topsoil acidification and depletion, promoting heavy metal activation and accumulation. On the other hand, the long-term combined application of pig manure and chemical fertilizer significantly promoted the enrichment of heavy metals in the topsoil and the activation of heavy metals in the soil profile. Therefore, in agricultural practices, it is recommended to optimize the application rates of chemical fertilizers, use treated pig manure and implement soil and water conservation measures to reduce the risks of heavy metal accumulation and non-point source pollution. |
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