Are Foliar Fertilizers Beneficial to Growth and Yield of Wild Lowbush Blueberries?

Abstract

Wild lowbush blueberry is an economically and culturally important crop in North America. Different fertilizer companies have been advertising their foliar fertilizer products to the wild blueberry growers, claiming better growth and production of this crop with no scientific proof. Although foliar fertilization has shown to be efficient for delivering micronutrients in deficit for different crops by reducing soil activation and environmental contamination, limited research has been done in wild blueberries. It is still unknown how foliar fertilizers affect the physiology, growth, and yield of this crop. Therefore, we tested the impacts of seven foliar treatments containing macro- and micro-nutrients and plant hormones (Seacrop16, Salvador, Agro-Phos applied in 2019 and Kali-T, Nano-Gro, Poma, Poma + Nanocellulose applied in 2020) on this crop for one crop cycle from vegetative year (2019) to crop year (2020). We tested these products against the standard soil-applied granular fertilizer called Diammonium phosphate (DAP) and control (no fertilizer) in a randomized complete block design with eight replicates in a conventional wild blueberry field in Maine, USA. In 2019, no significant differences across the applied treatments were observed in crop physiology and growth except in leaf chlorophyll concentration. In 2020, there was significantly higher leaf chlorophyll concentration in SeaCrop16 and Poma+Nanocellulose plots, but significantly lower photosynthetic rates in DAP and SeaCrop16 treated plots compared to the control. Meanwhile, no significant differences in plant height, leaf characteristics, or blueberry yield were found among the treatments. Overall, mobile nutrients (N, P, K) from soil applied fertilizers and foliar fertilizers containing other immobile nutrients (Ca) and/or plant hormones might benefit crop growth, but the impact on yield is limited. We also reveal that the wild blueberry physiological and morphological traits and leaf nutrients in the vegetative year are more related to the crop yield than those traits in the crop year. This implies that a combination of wild blueberry physiology, morphology, and leaf nutrients in the vegetative year largely impact their yield in the following crop year.