Long-term effects of herbicide and fertilizers on lowbush blueberry growth and production

Abstract

Effects of herbicide and herbicide-fertilizer combinations on vegetative and reproductive growth of the lowbush blueberry (Vaccinium angustifolium Ait.) were assessed over a 12-yr period (six production cycles). All treatments stimulated stem lengths, fruit buds per stem and fresh fruit yields compared with untreated controls, but only after 3–6 yr. After the second cycle, stem lengths and fruit bud numbers were greater 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 1982, except in 1988. Nitrogen levels were greater in leaves and rhizomes of plants in all herbicide and herbicide + fertilizer plots than in control plots after 10 yr, whereas phosphorus was higher only in plants fertilized with NPK. These results suggest the lowbush blueberry responds slowly to herbicide and fertilizer applications. Increased vegetative and reproductive development, as well as denser plant stands, resulted from repeated herbicide and fertilizer applications. Fertilizers applied in conjunction with herbicides stimulate vegetative growth (and fruit buds if an NPK fertilizer), but appear to have no consistent effect on fresh fruit yields. Key words:Vaccinium angustifolium, fertilizer, herbicide, fruit buds, yield