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Crops receiving inorganic fertiliser have low heavy metal contents

The contents of arsenic, lead, cadmium and mercury in Danish crops applied with inorganic fertiliser or livestock manure are below the maximum permissible levels for these in feedstuff. These are the results of a study undertaken by the Department of Agroecology at Aarhus University.

2013.07.03 | Søren Tobberup Hansen

Scientists at Aarhus University have examined the contents of heavy metals in crops supplied with either inorganic fertiliser or livestock manure. Crop contents of heavy metals were below the limits applicable to livestock feed materials. Photo: Janne Hansen

Work is underway at EU level to impose limits on the contents of heavy metals in inorganic fertilisers. The ambition is to protect soil resources and to secure a food supply that poses no risk to health. As part of this work, the Ministry of Food, Agriculture and Fisheries commissioned Aarhus University to produce a report that examined how the use of inorganic fertiliser affects the heavy metal contents in crops grown under normal field conditions in Denmark. This report has now been published.


The report covers the contents of arsenic, lead, cadmium, chromium, mercury and nickel in maize, barley, clover and winter wheat grown at different levels of fertilisation (from unfertilised to twice the standard amount). The effect of inorganic fertiliser was compared with that of livestock manure.


The content of arsenic in the crops was barely detectable, irrespective of the level of fertilisation. The contents of lead, chromium, mercury and nickel were generally low and could not be related to the amounts of fertiliser applied.


For crops that received inorganic fertiliser around the period of growth, a direct correlation was found between the amount of fertiliser applied and crop cadmium content. But the cadmium content of crops was in all situations below the maximum limits for feed stipulated by the EU. Especially barley and wheat had very low levels of cadmium.


Professor Bent Tolstrup Christensen, who has been in charge of the report, concludes on the background of the results that the agricultural use of inorganic fertilisers does not pose a problem in terms of complying with the maximum permissible levels:


- Even with prolonged use of inorganic fertilisers in the quantities and qualities we have examined, the contents of arsenic, lead, cadmium and mercury in typical agricultural crops do not exceed the maximum permissible levels of these metals in the feed material. This is a positive result for both animals and humans.


The data for the report consists of analyses carried out on crops grown from 2009 to 2012 in the long-term fertiliser experiments at Askov Experimental Station (Denmark), results from previous Danish field trials, and results from two field trials conducted in Skåne (southern Sweden) from 2009 to 2012. No systematic differences were found in analysed heavy metal contents between the use of inorganic fertiliser and livestock manure. The cadmium content, however, was lower with the use of livestock manure. The maximum levels for arsenic, lead, cadmium and mercury in feed have been set by the Ministry of Food, Agriculture and Fisheries; no limits have been set for chromium and nickel.



DCA report no. 24, June 2013 (in Danish)”Handelsgødnings indflydelse på afgrøders indhold af arsen, bly, cadmium, krom, kviksølv og nikkel” can be dowmloaded here.


Further information: Professor Bent Tolstrup Christensen, Department of Agroecology, telephone:  +45 8715 7764, e-mail: bent.t.christensen@agrsci.dk


Associate professor Lars Elsgaard, Department of Agroecology, telephone:  +45 8715 7674, e-mail: lars.elsgaard@agrsci.dk





Research, Public / media, Agriculture and food, Crops