The effect of soil texture on water use efficiency (WUE) was analyzed for six crops cultivated on loam and
clay soils. Results were obtained after a long-term study, carried out in a lysimetric set-up, in conditions
of experimental neutrality (climate, agro-techniques, and variety were the same for each crop) with the
sole exception of the soil texture, which was the variable to be studied.
In the case of potato, corn, sunflower, and sugar beet, WUE was reduced significantly when crops were
grown in clay soil. The reductions ranged from 22% to 25%. The decrease of WUE in clay soil was coupled
with significant reductions in yield and in ET, except in the case of the corn crop. The reduction in WUE
in corn depended solely on the yield decrease.
A 10% decrease in WUE values was also observed for the soy-bean and tomato grown in clay soil, but it
was not statistically significant.
Different causes which may reduce the WUE values observed in the clay soil are discussed. It seems
coherent to hypothesize that, during the active growing phase, a deficit in water uptake occurs in the plants
growing in the clay soil. This hypothesis is consistent with the observations of stomatal conductance, daily
evapotranspiration, and leaf surface.
In conclusion, the operative development of this study is outlined