The soil is neutral to slightly alkaline and the soil
is virtually free of carbonate. The carbon content is in the normal
range usually for agricultural soils (Table 1). More information on
the soil characteristics can be found in Krebs et al. [53].
In France, durum wheat is cultivated on 400 000 ha, mostly in
the South, and yielded a production of 2 Mton in 2009. T. turgidum
L. cv. Claudio W. was grown in the Rafz soil with and without Si
applications. We applied a natural ASi powder (siliceous fossil
meal, Clarcel 78®) that had been extracted from a diatomite mine
exploited by CECA (ARKEMA Group) from Saint-Bauzile (France),
which contains 87% SiO2 and makes it interesting because it is
rather concentrated. The remaining 13% include Al, Fe, Ca, Mg and
K. ASi is an opal A-like mineral that was chosen because it has been
shown to dissolve easily [54].