Response of Highbush Blueberry to Nitrogen Fertilizer During Field Establishment, I: Accumulation and Allocation of Fertilizer Nitrogen and Biomass

Abstract

The effects of nitrogen (N) fertilizer application on plant growth, N uptake, and biomass and N allocation in highbush blueberry (Vaccinium corymbosum L. ‘Bluecrop’) were determined during the first 2 years of field establishment. Plants were either grown without N fertilizer after planting (0N) or were fertilized with 50, 100, or 150 kg·ha−1 of N (50N, 100N, 150N, respectively) per year using 15N-depleted ammonium sulfate the first year (2002) and non-labeled ammonium sulfate the second year (2003) and were destructively harvested on 11 dates from Mar. 2002 to Jan. 2004. Application of 50N produced the most growth and yield among the N fertilizer treatments, whereas application of 100N and 150N reduced total plant dry weight (DW) and relative uptake of N fertilizer and resulted in 17% to 55% plant mortality. By the end of the first growing season in Oct. 2002, plants fertilized with 50N, 100N, and 150N recovered 17%, 10%, and 3% of the total N applied, respectively. The top-to-root DW ratio was 1.2, 1.6, 2.1, and 1.5 for the 0N, 50N, 100N, and 150N treatments, respectively. By Feb. 2003, 0N plants gained 1.6 g/plant of N from soil and pre-plant N sources, whereas fertilized plants accumulated only 0.9 g/plant of N from these sources and took up an average of 1.4 g/plant of N from the fertilizer. In Year 2, total N and dry matter increased from harvest to dormancy in 0N plants but decreased in N-fertilized plants. Plants grown with 0N also allocated less biomass to leaves and fruit than fertilized plants and therefore lost less DW and N during leaf abscission, pruning, and fruit harvest. Consequently, by Jan. 2004, there was little difference in DW between 0N and 50N treatments; however, as a result of lower N concentrations, 0N plants accumulated only 3.6 g/plant (9.6 kg·ha−1) of N, whereas plants fertilized with 50N accumulated 6.4 g/plant (17.8 kg·ha−1), 20% of which came from 15N fertilizer applied in 2002. Although fertilizer N applied in 2002 was diluted by non-labeled N applications the next year, total N derived from the fertilizer (NDFF) almost doubled during the second season, before post-harvest losses brought it back to the starting point.