J. M. Faci Associate Member, ASCEDept. of Soils and Irrig., Lab. for Agronomy and the Environment (DGA-CSIC), Servicio de Investigación Agroalimentaria, DGA, Apdo. 727, E-50080 Zaragoza, Spain.Dept. of Genetics and Plant Production, Lab. for Agronomy and the Environment (DGA-CSIC), Estación Experimental de Aula-Dei, CSIC, Apdo.202, E-50080 Zaragoza, Spain. E-mail:
[email protected]. of Soils and Irrig., Lab. for Agronomy and the Environment (DGA-CSIC), Servicio de Investigación Agroalimentaria, DGA, Apdo. 727, E-50080 Zaragoza, Spain. E-mail:
[email protected];
[email protected]