Research in the UK has shown that sodium and potassium can substitute for one another as plant nutrients; however, both sodium and potassium are needed to some degree by the sugar beet crop. Sodium increases leaf area early in the growing season and improves the efficiency of leaves under conditions of moderate water stress. Under drier growing conditions, sodium may be responsible for increased root yield and sugar content. The detrimental effect of increased soil sodium levels is that sodium root impurities increase.