ARS | Publication request: Effects of nitrogen source and rate and method of fertilizer application on yield and fruit size in 'Bluecrop' highbush blueberry

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: May 31, 2011
Publication Date: September 1, 2011
Citation: Vargas, O., Bryla, D.R. 2011. Effects of nitrogen source and rate and method of fertilizer application on yield and fruit size in 'Bluecrop' highbush blueberry. HortScience. 46(9):S286.

Technical Abstract: A study was done to determine the effects of N source and rate and two common methods of fertilizer application on yield and fruit size in a maturing field of highbush blueberry. Plants were fertilized by drip fertigation or with granular fertilizer using urea or ammonium sulfate applied at a rate of 0, 67, 133, and 200 kg/ha N in 2008 (year 3), 0, 75, 150, and 225 kg/ha N in 2009 (year 4), and 0, 83, 167, and 250 kg/ha N in 2010 (year 5). Liquid fertilizer was injected weekly (fertigation) from mid April to mid August in plants irrigated using a single lateral of drip in 2008 and 2009 and two laterals of drip in 2010. Granular fertilizer was split into three equal applications in mid April, mid May, and mid June in plants irrigated by microsprays. In 2008, which was the first year of fruit production, fertigation increased yield compared to granular fertilizer, while N source had no effect on yield in fertigated plants but was higher on average with granular urea than with granular ammonium sulfate. Average individual berry weight was also higher with fertigation than granular fertilizer and, regardless of application method, was greater when plants were fertilized with 67 kg/ha N. The following year in 2009, yield was again higher with fertigation than with granular fertilizer, and berry weight was affected by N rate, decreasing from an average of 1.6 g/berry without N to 1.4 g/berry with 225 kg/ha N. Finally, in 2010, yield was again higher with fertigation than with granular fertilizer but was not affected by N source or N rate. The average size of the berries, however, was smaller with fertigation than with granular fertilizer in 2010. Berry weight also decreased that year when high rates of N were applied. Overall, regardless of N source, yield was higher each year with fertigation than with granular fertilizer, and 67-83 kg/ha N was adequate to maximize yield and fruit size during the first 3 years of production.