Effects of nearly four decades of long-term fertilisation on the availability, fraction and environmental risk of cadmium and arsenic in red soils

The results of this study show how poorly managed long-term fertilisation can lead to cadmium (Cd) and arsenic (As) accumulation in soils and crops. To remedy this situation, the researchers make recommendations, including controlling and reducing the level of heavy metals in fertilisers.

While this study recognises the value of fertiliser use in agricultural practices due to its effective ability to promote crop productivity, it also points out how long-term and poorly managed fertilisation can cause dramatic damage due to heavy metal accumulation in soils and crops¹.

In particular, this research reports the impacts of long-term fertilisation on arsenic and cadmium accumulation at the Qiyand Agricultural Station in Hunan Province, renamed Red Soil Experiment Station.

Red soils are mainly located in subtropical regions of China, particularly in the Jiangxi and Hunan provinces. There are characterised by their acidic nature and depleting nutrient levels (nitrogen, phosphorus and potassium), which partly explains why typical agricultural management activities have always been accompanied by intensive use of chemical fertilisers.

As there is an almost half-century-history of long-term fertilisation practices on the rice fields of the Qiyand Agricultural Station, it appears to be an ideal site to conduct long-term experiments and assessments to gain reliable information on the environmental, ecological and safety risks of fertiliser application and its potential contamination of soils and crops with heavy metals.

The results of the study indicate that soils treated with fertilisers, including inorganic nitrogen, phosphorus and potassium fertilisers, had significantly raised levels of total and available Cd and As concentration after long-term fertilisation. Specifically, the research establishes that Cd is more likely to accumulate in soils themselves, while As tends to concentrate more in the rice plants. As highlighted in the risk assessment results, this indicates significantly higher environmental risks associated with fertiliser use.

To address this accumulation of heavy metals and their entry into the food chain, the study suggests the implementation of reasonable management practices for long-term fertilisation. One of their key recommendations is to control the source of heavy metals, including by reducing the level of heavy metals contained in organic and inorganic fertilisers, and by identifying crop-plants that accumulate low levels of contaminants.