The increasing use of organic fertilizers has raised alarms about their potential impact on soil and crop safety, particularly concerning heavy metal contamination. A recent study has revealed concerning levels of heavy metals within commercial organic fertilizers (COFs) produced across China.
Researchers conducted extensive analyses on 74 typical COFs utilizing inductively coupled plasma mass spectrometry (ICP-MS) to assess concentrations of various heavy metals like arsenic, mercury, lead, cadmium, chromium, copper, zinc, and nickel. Their findings unveiled alarming statistics: concentrations of arsenic ranged from 1.55 to 36.95 mg/kg, mercury from 0.04 to 2.32 mg/kg, and certain fertilizers showed particularly hazardous levels of zinc and nickel, with maxima reaching 2705.68 mg/kg and 244.47 mg/kg, respectively.
Comparing these findings against China's Organic Fertilizer Standard (2021) and the European Union's regulations, the research indicated significant rates of exceedance. For example, 45.95% of the tested COFs exceeded arsenic limits established by Chinese standards, and the more stringent EU standards showed even higher levels of concern, particularly for copper, zinc, and nickel.
The authors of the study warn of the potential accumulation risks these fertilizers pose to farmland over time. “The application of organic fertilizers from different raw materials has the greatest risk of exceeding Cd [cadmium] in soil, and the maximum application period is below 50 years,” they noted. Continuous use of certain COFs could raise cadmium levels above safety thresholds within just 20 years if used on plant-based and pig manure-based fertilizers.
This issue has arisen amid the unprecedented growth of COFs across China’s agricultural sector, reportedly increasing market size by 17 times since 2014, culminating at approximately $150 billion by 2022. Given such widespread application, it becomes increasingly important to monitor heavy metals' content within these fertilizers.
With heavy metals like copper and zinc often added to livestock feeds to promote growth, their presence in organic fertilizers reflects the broader dynamics of agricultural practices today. The research indicates the need for stringent oversight of these materials, particularly ensuring they meet health and safety standards.
Cautions raised by the study point to the broader issue of soil pollution and its potential ripple effects on food security and human health. Excessive levels of cadmium, for example, could significantly increase the risks related to contaminated crops, particularly rice, if produced under conditions of heavy metal accumulation.
“The heavy metals concentrations of organic fertilizers made from different sources had exceeded the standard of Cu, Zn, and Ni,” the authors added, emphasizing the regulatory gap currently observed in China. There exists no specified limit for these heavy metals within the country’s organic fertilizer standards, highlighting the urgent need for regulatory standards to protect soil health and, by extension, human health.
The analysis concluded by underscoring the importance of regulating heavy metals within COFs and monitoring soil health to mitigate pollution risks. Prioritizing these areas will not only safeguard farmland but also secure future food safety as the agricultural sector continues to evolve.