Nitrogen Requirement of the Highbush Blueberry, Vaccinium corymbosum L.1

Field applications of N greater than 34 kg/ha to highbush blueberry plants on an Atsion sand did not result in increased fruit production. Application of more than 64 kg N/ha may be detrimental to blueberry production. The optimum N content in the median leaves sampled one month after harvest of lateral shoots averaged 1.65% N over a 5 year period. A biennial bearing pattern occurred consistently at each of N fertilizer levels. Leaf N levels tended to be lower during years of high production than during years of low fruit production. Ca levels in leaf tissue were found to be below the sufficiency level during low production years when leaf N was high and above the sufficiency level in high production years when leaf N was lower.