A low pH of the soil prevents the specific apple replant disorder (SARD). Not much is known about the effect of a low pH on the growth of fruit trees. Most authors accept a pH of between 5.5 and 6.5 as optimum for apples but this assumption is not based on experimental research. It is feasible that apple trees grow well at a lower pH than has hitherto been accepted. The influence of a low pH on bitter pit needs careful examination.