NORTH-SOUTH CENTRE - ETH - North-South Centre North-South ...

Zinc fluxes from the soil into the food chain
in arid agro-ecosystems – A case study in Iran
Zinc (Zn) deficiency is considered a major global problem
in human nutrition, particularly in arid regions where the
population depends on cereals as staple foods. In this project
in central Iran, we are performing a case study on Zn
fluxes from the soils into the crop plants and from agricultural
food products into human nutrition. The goals
are (i) to analyse the effects of agricultural practices on
grain Zn and phytate concentrations in cereals, (ii) to
assess the impacts of these cereals on human nutrition,
and (iii) to evaluate agricultural options which reduce
dietary Zn deficiency.
We performed a field survey assessing soil Zn concentrations,
various soil and climate factors known or suspected
to directly or indirectly influence the bioavailability of soil
Zn, and the grain Zn concentrations of cereals grown on
the sampling sites. The analysed soil and climate variables
explained only a small part of the total variance in grain
Zn. The analysis of Zn fluxes into agricultural soils revealed
that, in general, Zn inputs by fertilisation exceed outputs
through harvest by 1–2 kg Zn per ha and year. On average,
manure and inorganic fertilisers contribute equally to the
inputs. As expected, these data demonstrate that problems
of insufficient Zn supply to crops are not due to ab-
solute Zn deficiency in the soils, but to insufficient Zn bioavailability.
In summary, the results suggest that there is
substantial scope for increasing grain Zn concentrations
in cereals. Appropriate agricultural management practices
could enhance soil Zn bioavailability without excessive Zn
fertilisation – also on soils where conditions appear to be
rather unfavourable for Zn uptake by crop plants.
In addition, we performed two surveys on human Zn intake
using the method of three-day weighted food records –
one in a suburban community and the other in a village. In
both populations, the major staple foods were bread and
rice. The consumption of meat and dairy products differed
considerably between households, depending primarily on
economic conditions. This was more evident in the suburban
population where variations in the economic conditions
of the participating families were larger than in
the village population. Comparing the calculated total Zn
intake rates with RDA (Recommended Daily Allowance)
reference values suggests that Zn deficiency is in fact a
mineral malnutrition problem in parts of the sampled
populations. Serum samples taken from the participants
are currently being analysed in order to obtain information
on their physiological Zn status.
Project leaders
Rainer Schulin
Richard Hurrell
Emmanuel Frossard
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Contact persons
Manouchehr Amini, ETH Zurich
Mahin Karami, IUT Isfahan, Iran
Nazanin Roohani Sharaki, ETH Zurich
Collaborators
Majid Afyuni and Amir Khoshgoftarmanesh,
IUT Isfahan, Iran;
Rita Wegmüller, ETH Zurich, Switzerland;
Claudia Binder, University of Graz, Austria;
Armin Keller, ART, Switzerland
Duration
July 2007 – June 2010
Thematic cluster
Food quality and public health
Research collaboration
Livestock systems research
On-campus bakery, Isfahan University of Technology (IUT), Iran