ARS | Publication request: A Comparison of Continuous Nitrogen Fertigation to Conventional Granular Fertilizer Application in Highbush Blueberry

Submitted to: Blueberry Research Extension North American Workers Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 6, 2010
Publication Date: July 25, 2010
Citation: Bryla, D.R., Vargas, O. 2010. A comparison of continuous nitrogen fertigation to conventional granular fertilizer application in highbush blueberry. Blueberry Research Extension North American Workers Conference Proceedings. p.26.

Technical Abstract: Nitrogen fertigation practices are currently being evaluated and compared to conventional fertilizer aplication on 0.6 acres of 'Bluecrop' blueberry planted April 2006 in Corvallis, OR. Plants are spaced 2.5 x 10 ft. apart and growing on mulched, raised beds. Treatments include two methods of fertilizer application (fertigation and granular fertilizer), two types of fertilizer (urea and ammonium sulfate), and four fertilizer rates (0, 67, 133, and 200 lb/acre N in 2009; lower rates were applied in previous years, and rates were increased each year to adjust for changes in plant size). The fertigation treatments are irrigated by drip while the granular fertilizer treatments are irrigated by microsprays (simulates sprinklers). Liquid urea (20-0-0) or liquid ammonium sulfate (9-0-0) are injected weekly into the drip lines, beginning in mid-April (leaf emergence) and continuing until mid-August (about 60 days prior to the end of the growing season). Granular urea (46-0-0) or granular ammonium sulfate (21-0-0) are applied monthly in three equal doses from April to June (triple-split). Early results indicate that continuous fertigation at 135 lb/acre of N produced the most growth among treatments during the first 2 years after planting (2006-2007); however, much less N was needed (60-67 lb/acre) to maximize yield in each treatment during the third and fourth year after planting (2008-2009). Increased growth and yield were associated with better soil conditions (i.e., pH, electrical conductivity) but was not attributed to higher N uptake than granular fertilizer application. The study will continue until plants reach full production.