EFFECTS OF ORGANIC FERTILIZER APPLICATION ON AMERICAN CRANBERRY CULTIVATION - MINERAL NUTRITION STATUS, PLANT VITALITY AND POSSIBLE ENVIRONMENTAL ASPECTS

The cultivation of American cranberries (Vaccinium macrocarpon Aiton) with organic fertilizers is becoming more common in the world. With 180 ha of producing plantings and 376 tonnes of yearly production, Latvia is one of the largest cranberry producers in the world. The lack of knowledge on fertilization management can be an obstacle to a successful transition to organic farming. The objective of this study was to test the effect of organic fertilizer of animal origin on cranberry mineral nutrition status, plant vitality, vegetative growth and berry yield. Field experiments on cranberry cultivar Bergman were conducted during 2022-2023 in a commercial plantation established on cutover peat bog in Latvia. In the spring of both experimental years, cranberries received five levels (1, 2, 3, 4, and 5 t ha-1) of certified pelleted organic fertilizer FERTIPLUS (4-3-3-65 OM). Two control treatments - without fertilizer and conventional fertilizer with Novatec Classic (12-8-16+3+TE) - were also established. The results showed that even the highest doses of organic fertilizer added in 2022 did not affect the nutrient content in the peat in 2023 at the beginning of vegetation, thus indicating a high release of plant-available nutrients in the first year. Nutrient release process occurred over a longer period than from conventional fertilizer, reaching maximum in August. Adjustment of the organic fertilization strategy is needed to account for the slow release pattern and synchronize with the cranberry growth phases.