Effect of low soil pH from different fertilisers on performance of apple and pear trees

Abstract

Many orchard soils in northcentral Washington have approximately neutral pH. Years of applying fertilisers to fruit trees in this area have resulted in unacceptably low pH values of the soil requiring lime to correct it. In the experimental apple orchard, soil pH values ranged from 4.1 to 6.9 at the end of the fifth year of fertilizer application. Increased fruit size and improved red coloration of ‘Red Delicious’ apple skin was related to higher soil pH values. Both of these attributes are important for high quality fruit. In the pear orchard, soil pH values ranged from 3.9 to 5.6. Neither apple nor pear growth nor fruit production was related to soil pH values in these two orchards. However, tree vigour and yield of apple trees tended to be higher at soil pH values of approximately 5.6 and 6.3, respectively.