Optimizing Nitrogen Rates for Commercial Southern Highbush Blueberry Production During Establishment Yang Fang Graduate Student David Liu and Jeff Williamson Horticultural Sciences Department IFAS, University of Florida
Objective To determine optimum N rates for growth and early yield of young southern highbush blueberry plants.
Materials and Methods 5 N rates (lbs. N/a): T1: 0 T2: 37 T3: 75 Nitrogen source: UAN-32 5 replicates, 6 plants/plot I have 5 nitrogen treatments with 5 replicates. Each replicate has 6 plants. N fertilizer used in this experiment is UAN-32
‘Farthing’ ‘Emerald’
UF Plant Science Research and Education Unit in Citra, FL 3 feet 8 feet
Pine bark was incorporated into the top 6 inches soil Date: 2/24/15 Preplant rate is about 180 kg/ha 2/24/15 Fertigation starts at April 1 First soil sampling 4/29/15
Fertigation System Drip irrigation rate: 1.48 L/day/ plant Fertigation: 242 days/year
Measurements Leaf N content Percentage of groundcover (1st year) Total yield (2nd year) Average berry weight (2nd year) Berry firmness and diameter (2nd year) SSC/TTA (2nd year) canopy area measured by an image-processing program ImageJ
NS NS NS NS There is no significance difference in leaf nitrogen among treatments.
NS NS NS NS
Figure 2-3. Effect of nitrogen fertigation rate on percent groundcover of young ‘Emerald’ blueberry plants in 2015.
0 N/a, September 22, 2016
37 lbs. N/a, September 22, 2016
150 lbs. N/a, September 22, 2016
300 lbs. N/a, September 22, 2016
Effect of nitrogen fertigation rate on percent groundcover of young ‘Farthing’ blueberry plants, 2015.
0 lbs. N/a, September 22, 2016
37 lbs. N/a, September 22, 2016
150 lbs. N/a, September 22, 2016
300 lbs. N/a, September 22, 2016
Effect of nitrogen fertigation rate on fruit yield per plant of young ‘Emerald’ blueberry plants in 2016.
Effect of nitrogen fertigation rate on fruit yield per plant of young ‘Farthing’ blueberry plants in 2016.
Effect of nitrogen fertigation rate on average berry weight of young ‘Emerald’ blueberry plants.
Effect of nitrogen fertigation rate on average berry weight of young ‘Farthing’ blueberry plants.
Effect of nitrogen fertilizer rate on fruit firmness and diameter of young ‘Emerald’ and ‘Farthing’ blueberry plants in the early season.
Effect of nitrogen fertilizer rate on fruit firmness and diameter of young ‘Emerald’ and ‘Farthing’ blueberry plants in mid-season.
Effect of nitrogen fertilizer rate on fruit firmness and diameter of young ‘Emerald’ and ‘Farthing’ blueberry plants in late season.
Effect of N fertilization rate on SSC/TTA ration of ‘Emerald’. Emerald' SSC/TTA ratio N (lb/a/yr) early season mid season late season 11.47a 13.37a 15.94a 37 11.83a 11.62a 15.47a 75 11.64a 12.45a 15.08a 150 12.64a 12.43a 17.69a 300 13.69a 13.54a 18.75a
Farthing' SSC/TTA ratio Effect of N fertilization rate on SSC/TTA ration of ‘Farthing’. Farthing' SSC/TTA ratio N (lb/a/yr) early season mid season late season 11.51ab 14.11a 15.63bc 37 10.33b 11.95a 14.70c 75 12.11ab 14.52a 16.10bc 150 13.97a 14.64a 19.71ab 300 12.00ab 12.84a 21.98a
Conclusions There were no significant differences in leaf N content among N treatments. Percent groundcover of plants receiving150 lbs N/a and 300 lbs N/a were similar, and were significantly larger than other treatments. Fruit yield (year 2) of plants receiving150 lbs N/a were similar to the 300 lbs N/a treatment and higher than lower N treatments. The 300 lbs N/a treatment produced fruit that tended to be smaller and firmer than other N treatments. N fertilization rate did not affect SSC/TTA ratios for ‘Emerald’ Lower N rates tended to result in reduced SSC/TTA ratios for “Farthing’. According to the fruit yield regression, the optimum N rate for young ‘Emerald’ is 222 kg/ha/yr and for ‘Farthing’ is 206 kg/ha/yr.
Acknowledgements Eric Ostmark, Moshe Doron, Kim Cordasco, Adrian Berry, Carol Hamilton USDA-AMS
Thank you! Questions?