|Banados, M. Pilar -|
|Strik, Bernadine -|
|Righetti, Timothy -|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 16, 2012
Publication Date: May 1, 2012
Citation: Banados, M., Strik, B., Bryla, D.R., Righetti, T.L. 2012. Response of highbush blueberry to nitrogen fertilizer during field establishment. I. Accumulation and allocation of fertilizer nitrogen and biomass. HortScience. 47(5):648-655. Interpretive Summary: No work has been published to date on N fertilizer uptake and partitioning in young, field-grown blueberry plants. The objectives of our study were to determine the impact of N fertilizer application on N uptake, partitioning, and growth of young, field-grown blueberry plants during the first 2 years of establishment. Nitrogen required for growth in young highbush blueberry plants came from fertilizer and soil sources and from remobilization of N stored in the plant. Plant growth and partitioning were affected by N fertilizer rate. The best N fertilizer rate for plant growth was 50 kg/ha of N, which resulted in larger plants, greater total plant N, and the highest fruit yield. Fertilization with higher rates of N reduced plant growth and increased plant losses. Unfertilized plants, in comparison, were smaller and contained less N than those fertilized with 50 kg/ha of N. We do not know if lower rates of N fertilizer would have been sufficient in these young plants, as lower rates were not applied.
Technical Abstract: The effects of N fertilizer rate on plant growth, N uptake, and biomass and N partitioning was studied in highbush blueberry during the first 2 years after planting. Plants were grown without N fertilizer or with either 50, 100, or 150 kg/ha N applied each year using 15N-depleted ammonium sulfate the first year and non-labeled ammonium sulfate the second year. The lowest rate, 50 kg/ha N, produced the best plant growth and yield, while 100 and 150 kg/ha N were excessive and reduced total plant dry weight (DW), total N, and uptake of N fertilizer, and resulted in 17-55% plant mortality by the end of year 1. Fertilizer N was found in every plant part, and allocation varied throughout the year. At the time of maximum fertilizer recovery, N from fertilizer accounted for 58-70% of total N in the plants, depending on N rate. Unfertilized plants allocated similar amounts of DW to new canes, crown, and roots as fertilized plants but much less biomass to leaves and fruit. They also had less total plant N than fertilized plants. By the end of year 1, unfertilized plants gained 1.6 g/plant of N from soil sources, while fertilized plants accumulated 2.3 g/plant of N, with 60% of this gain from fertilizer N and only 0.9 g/plant from the soil. Similar results were observed in the second year of the study. After fruit harvest in year 2, fertilized plants grew very little from July through October, while DW of unfertilized plants increased. Similarly, total N content of fertilized plants remained relatively stable after fruit harvest, whereas N content of unfertilized plants continued to increase in this same time period from soil-available N. By January at the beginning of year 3, unfertilized plants accumulated 3.6 g/plant of N. In comparison, plants fertilized with 50 kg/ha N accumulated 6.4 kg/ha of N, but, by this point, only 20% of the accumulated N came from fertilizer.