A comparison between fertigation and granular fertilizer applications on yield and leaf nitrogen in red raspberry

A study was conducted in 2011 and 2012 to compare the effects of applying N by fertigation or as granular fertilizer on yield and leaf N in 'Meeker' red raspberry (Rubus idaeus). The planting was established in April 2006 at site located in western Oregon, USA. Plants were irrigated by drip or sprinklers and grown with or without N fertilizer. With drip, N was applied by 1) fertigation through the drip system using liquid sources of ammonium nitrate, calcium ammonium nitrate, or urea ammonium nitrate from mid-April to mid-July, 2) split applications of granular calcium nitrate or calcium ammonium nitrate in mid-April and early June, or 3) a single application of granular calcium ammonium nitrate in mid-April followed by fertigation using the three liquid N sources from early June to mid-July. With sprinklers, N was applied at the same time and rate as drip, but only with split applications of the granular fertilizers. The first year, the plants grown without N were chlorotic and had lower leaf N concentrations than those grown with N fertilizer. Leaf N was also lower with sprinklers than with drip but was similar among the fertilized drip treatments, regardless of N source or the application method. Only the drip and sprinkler treatments fertilized with calcium ammonium nitrate were harvested by hand in 2011. As with leaf N, yield was also lower with sprinklers (10.8 t center dot ha(-1)) than with drip (14.6 t center dot ha(-1)) in 2011 and was similar among the drip treatments. All of the treatments were machine harvested the following year. On average, yield continued to be lower with sprinklers (6.1 and 2.5 t center dot ha(-1) with and without N, respectively) than with drip (13.5 and 10.6 t center dot ha(-1) with and without N, respectively) in 2012 but was no longer similar among the fertilized drip treatments. At this point, drip-irrigated plants fertigated with ammonium nitrate or calcium ammonium nitrate had lower yields (7.4 and 11.2 t center dot ha(-1), respectively) than those fertigated with urea ammonium nitrate (14.2 t center dot ha(-1)) or with one or two applications of granular fertilizer (an average of 15.1 t center dot ha(-1)). Overall, the plants produced more yield with drip than with sprinklers but, when irrigated by drip, had the same or lower yields with fertigation than with granular fertilizer.