LONG-TERM EFFECTS OF HERBICIDE AND FERTILIZERS ON LOWBUSH BLUEBERRY GROWTH AND PRODUCTION

Effects of herbicide and herbicide-fertilizer combinations on vegetati ve and reproductive growth of the lowbush blueberry (Vaccinium angusti folium Ait.) were assessed over a 12-yr period (six production cycles) . All treatments stimulated stem lengths, fruit buds per stem and fres h fruit yields compared with untreated controls, but only after 3-6 yr . After the second cycle, stem lengths and fruit bud numbers were grea ter in herbicide + NPK-treated plants than in all others. Fresh fruit yields were variable throughout the study but were higher in herbicide and herbicide + fertilizer plots than in untreated controls after 198 2, except in 1988. Nitrogen levels were greater in leaves and rhizomes of plants in all herbicide and herbicide + fertilizer plots than in c ontrol plots after 10 yr, whereas phosphorus was higher only in plants fertilized with NPK. These results suggest the lowbush blueberry resp onds slowly to herbicide and fertilizer applications. Increased vegeta tive and reproductive development, as well as denser plant stands, res ulted from repeated herbicide and fertilizer applications. Fertilizers applied in conjunction with herbicides stimulate vegetative growth (a nd fruit buds if an NPK fertilizer), but appear to have no consistent effect on fresh fruit yields.