Acknowledgements
This work was funded by the “Fondo Mixto CONACYT-Gobiernodel estado de Campeche”, fund formed by the state government ofCampeche and the Mexican Council of Science and Technology, aspart of the project: “Evaluación del efecto de la aplicación de aguade riego con sales disueltas, sobre las propiedades fisicoquímicasdel suelo y sobre el rendimiento del cultivo de ca˜na de azúcar”,CAMP-2004-C02-5. Thanks are also due to Colegio de Postgradua-dos Campus Campeche and Campus Veracruz for financial support,and also to the M.C. Juan Manuel Hernández Pérez for his assistancein the formatting of the manuscript.