Page 44 - Green knowledge 2024

Photo: Erling Fløistad
Pesticide residues in organic fertiliser
In 2023, NIBIO analysed samples from 60 organic fertiliser products on the Norwegian
market, following earlier findings of problematic herbicide residues in plant nutrients
approved for organic farming.
“The study detected residues in 48% of Norwegian
and 64% of imported samples. Residues were most
common in pelleted (79%) and liquid fertilisers
(75%), but rare in growing media/compost (17%),”
explains research scientist Marit Almvik. The
clopyralid levels in liquid fertilisers were lower than
in 2021, suggesting progress by the industry in
reducing transfer of clopyralid to organic fertilisers.
Aminopyralid was not detected, and no pyralids were
found in compost. However, clopyralid was often
found in pelleted fertilisers, including those based on
livestock manure and insect frass, where it was
detected for the first time. Clopyralid levels above 50
µg/kg in the pelleted fertilizer may harm
clopyralid-sensitive plants, such as tomatoes, peas,
and lettuce, depending on dosage and use.
To avoid clopyralid residues, it is recommended to
exclude raw materials treated with clopyralid during
fertiliser production. The EU is introducing labelling
requirements for processed manure-based fertilisers
to raise awareness. The concentrations of other types
of pesticides were low and comparable to those
found in soils. Fungicide residues were most fre-
quent.
For professional users, pesticide residues in fertil-
isers can cause challenges, particularly in organic
production, where residues may breach regulations if
detected in the crops. The Fertiliser Regulation
requires preventive measures but does not set
thresholds for harmful levels. Based on findings,
NIBIO recommends including at least 39 pesticides,
their degradation products, and some plant toxins in
future analyses of organic fertilisers.
Purpose: To map pesticide residue levels in 60 organic fertiliser products available on the Norwegian market.
Funding: Norwegian Food Safety Authority
Contact: Research Scientist Marit Almvik, Division of Biotechnology and Food Production.
Email: marit.almvik@nibio.no | Phone: +47 957 28 015
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