1. Agriculture and Forestry Engineering Department, ETSIIAA, Universidad de Valladolid. Avenida de Madrid, 44, 34004 Palencia, Spain
2. Department of Agricultural and Environmental Sciences, EPSH, Universidad de Zaragoza, Carretera de Cuarte s/n, 22071 Huesca, Spain
3. Department of Plant Production and Forest Resources. ETSIIAA, Universidad de Valladolid. Avenida de Madrid, 44, 34004 Palencia, Spain