1. 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

2. Objective
To determine optimum N rates for growth and early yield of young southern highbush blueberry plants.

3. 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

4. ‘Farthing’
‘Emerald’

5. UF Plant Science Research and Education Unit in Citra, FL
3 feet
8 feet

6. 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

7. Fertigation System Drip irrigation rate: 1.48 L/day/ plant
Fertigation: 242 days/year

8. 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

9. NS NS NS NS
There is no significance difference in leaf nitrogen among treatments.

10. NS NS NS NS

11. Figure 2-3. Effect of nitrogen fertigation rate on percent groundcover of young ‘Emerald’ blueberry plants in 2015.

12. 0 N/a, September 22, 2016

13. 37 lbs. N/a, September 22, 2016

14. 150 lbs. N/a, September 22, 2016

15. 300 lbs. N/a, September 22, 2016

16. Effect of nitrogen fertigation rate on percent groundcover of young ‘Farthing’ blueberry plants, 2015.

17. 0 lbs. N/a, September 22, 2016

18. 37 lbs. N/a, September 22, 2016

19. 150 lbs. N/a, September 22, 2016

20. 300 lbs. N/a, September 22, 2016

21. Effect of nitrogen fertigation rate on fruit yield per plant of young ‘Emerald’ blueberry plants in 2016.

22. Effect of nitrogen fertigation rate on fruit yield per plant of young ‘Farthing’ blueberry plants in 2016.

23. Effect of nitrogen fertigation rate on average berry weight of young ‘Emerald’ blueberry plants.

24. Effect of nitrogen fertigation rate on average berry weight of young ‘Farthing’ blueberry plants.

25. Effect of nitrogen fertilizer rate on fruit firmness and diameter of young ‘Emerald’ and ‘Farthing’ blueberry plants in the early season.

26. Effect of nitrogen fertilizer rate on fruit firmness and diameter of young ‘Emerald’ and ‘Farthing’ blueberry plants in mid-season.

27. Effect of nitrogen fertilizer rate on fruit firmness and diameter of young ‘Emerald’ and ‘Farthing’ blueberry plants in late season.

28. 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

29. 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

30. 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.

31. Acknowledgements
Eric Ostmark, Moshe Doron, Kim Cordasco, Adrian Berry, Carol Hamilton
USDA-AMS

32. Thank you!
Questions?