A series of 695 food crops were collected on 539 soils throu
ghout Bel
giu
m. All sa
mples were collected on co
mmercial production fields, o
mittin
g private
gardens. All crops were analyzed for their seleniu
m (Se) concentration. The soils represent different soil types occurrin
g in Bel
giu
m, with soil textures ran
gin
g fro
m sand to silt loa
m, and includin
g a few clay soils. They were analyzed for Se concentration, or
ganic carbon content, cation exchan
ge capacity and extractable sulphur (S) concentration. The Se concentrations in the soils were low (ran
ge 0.14-0.70
mg k
g鈭?#xA0;1 dw), but increasin
g soil Se concentrations were observed with increasin
g clay content. Stepwise
multiple re
gressions were applied to deter
mine relations between Se concentrations in crops and soil characteristics.
Among field crops, wheat is the most important accumulator of selenium but the concentration remains rather low on the Belgian low Se-soils. Based on dry weight, leafy vegetables contain more Se than wheat. The soil is the most important source of Se and the element is transported with the water stream to the leaves, where it is accumulated. Vegetables rich in S, e.g. some m>Brassicam> and m>Alliumm> species, have a higher capacity to accumulate Se as it can replace S in the proteins, although this accumulation is still limited at low soil Se concentrations.
In loamy soils, weak correlations were found between the soil Se concentration and its concentration in wheat and potato. The uptake of Se increased with increasing pH. The Se concentrations in Belgian soils are far too low to generate a driving force on Se uptake. General climatic conditions such as temperature, air humidity and soil moisture are also important for the transfer of Se within the plant, and plant linked factors such as cultivar, growth stage and edible part are important as well, although their influence remains limited at low soil Se concentrations.