Presentation by University of Minnesota's Carl Rosen, Terry Nennich, and Jerry Wright at the 2009 Minnesota Statewide High Tunnel Conference in Alexandria, MN on Dec. 2-3, 2009.

1. Soil Fertility
Research in
High Tunnels
Carl Rosen, Terry Nennich, & Jerry Wright
University of Minnesota
High Tunnel Workshop
Alexandria, MN
© 2009 Regents of the2009
December 2-3, University of Minnesota

2. Topics
 Background (review)
 Fertigation study –
 Tomato 2008 and 2009
 Cucumber 2009 (spidermite problem in 2008)
 Compost vs. compost + fertigation
© 2009 Regents of the University of Minnesota

3. Yield Potential & Nutrient Needs
 Yields in a high tunnel can be 2 to 4 times the
yield obtained in the field
 Higher yields will required more nutrients, but
knowing how much to apply is a challenge
 Lack of nutrients – deficiencies
 Excessive nutrients – salt build up
 Both situations affect yield and quality
© 2009 Regents of the University of Minnesota

4. Tomato nutrient uptake
N P K
Plant Part -------- lb per ton F.W. ------------
Fruit 3.4 0.4 6.0
Vines 2.6 0.4 3.4
Total 6.0 0.8 9.4
A 50 ton yield/A would require:
300 lbs N/A
40 lbs P/A (92 lbs P2O5)
470 lbs K/A (564 lbs K2O)
© 2009 Regents of the University of Minnesota

5. Staples Fertigation Study
 High amounts of compost are often used
in high tunnels
 Objective:
 To determine if fertigation is needed for
tomato when compost is used
 Conducted at the Central Lakes College Ag
Center in©Staples in the University of2009
2009 Regents of 2008 & Minnesota

6. Staples High Tunnel
 20’ wide x
48’ length
© 2009 Regents of the University of Minnesota

7. Soil Test Properties in the Spring-
2008 (before compost application)
Soil Depth pH Organic Matter Soluble Salts
Inches % mmhos/cm
0-6 7.0 6.4 0.9
6-12 6.9 5.4 0.7
Soil Depth NO3-N Bray-P K
Inches lb/A --------- ppm ----------
0-6 61 174 89
6-12 43 144 103
 P was in the very high range, K was medium
© 2009 Regents of the University of Minnesota

8. Soil Amendments & Treatments
2008
 Yard waste compost added in 2008
 ~ 2.5 tons fresh (~50% moist) spread evenly
 ~ 5 lbs fresh per square ft
 0.64% N, 0.12% P, 0.18% K; C/N: 26.8
 725 lb N/A, 313 lb P2O5/A, 245 lb K2O/A
 Two treatments
 Fertigation
 UAN, Potassium nitrate, and Calcium nitrate
 No fertigation
 Two replications for tomato
 Nine© 2009 Regents of the University of Minnesota
plants per replication

9. Procedures - 2008
 ‘Cobra’ tomato
(indeterminate)
 Transplants planted May 9
 Double row beds 4 ft apart; 2
ft between plants
 One cup 20-20-20 (1 oz/gal)
applied to each transplant
© 2009 Regents of the University of Minnesota

10. Procedures - 2008
 Plots set up so that half
received fertigation and
the other did not
 Each plot received the
same amount of water
 Plants pruned periodically
 Tomatoes harvested:
July 24 – October 16
© 2009 Regents of the University of Minnesota

11. Staples High Tunnel in 2008
Not Fertigated
Fertigated
© 2009 Regents of the University of Minnesota

12. Fertigation Dates and Rates - 2008
Date Source oz N/100' lb N/A oz K2O/100' lb K2O/A
2-Jun 28% 0.48 3.2 0.0 0.0
11-Jun 28%+Knit 0.72 4.9 1.5 10.2
17-Jun 28%+Knit 0.72 4.9 1.5 10.2
24-Jun 28%+Knit 0.72 4.9 1.5 10.2
1-Jul 28%+Knit 0.82 5.6 2.0 13.6
8-Jul Knit+CaNit 1.03 7.0 2.0 13.6
15-Jul Knit+CaNit 1.03 7.0 2.0 13.6
22-Jul Knit+CaNit 1.03 7.0 2.0 13.6
29-Jul Knit+CaNit 1.03 7.0 2.0 13.6
15-Aug Knit+CaNit 1.03 7.0 2.0 13.6
12-Aug Knit+CaNit 1.03 7.0 2.0 13.6
18-Aug Knit+CaNit 1.03 7.0 2.0 13.6
28-Aug Knit+CaNit 1.03 7.0 2.0 13.6
10-Sep Knit+CaNit 1.03 7.0 2.0 13.6
Total © 2009 Regents of 12.7 University of Minnesota
the 86.5 24.5 166.6

13. Tomato Early Yields 2008
- First 3 Weeks-
Marketable
Treatment fruit number/plant fruit wt (lbs/plant)
Fertigated 7.5 ± 0.9 2.5 ± 0.3
Non-fertigated 8.8 ± 0.0 3.3 ± 0.1
 Fertigation tended to delay yield
© 2009 Regents of the University of Minnesota

14. Marketable Tomato Yields - 2008
Treatment fruit number/plant fruit wt. (lbs/plant)
Fertigated 27.5 + 0.3 10.1 + 0.3
Non-fertigated 29.9 + 3.1 13.2 + 1.1
Non-fertigated as good or
better than fertigated
Compost supplied enough
nutrients
© 2009 Regents of the University of Minnesota

15. Soil Test after Final Harvest
– Fall 2008
With fertigation
Soil Depth NO3-N Bray-P K Soluble Salts
Inches lb/A --------- ppm ---------- mmhos/cm
0-6 50 181 117 0.4
6-12 37 161 101 0.4
Without fertigation
Soil Depth NO3-N Bray-P K Soluble Salts
Inches lb/A --------- ppm ---------- mmhos/cm
0-6 36 193 76 0.4
6-12 26 145 75 0.3
© 2009 Regents of the University of Minnesota

16. © 2009 Regents of the University of Minnesota

17. Soil Test before Planting
– April 2009
With fertigation
Soil Depth NO3-N NH4-N Bray-P K Soluble Salts
Inches ----------- lb/A ----------- --------- ppm ---------- mmhos/cm
0-6 84 10 167 146 0.8
6-12 44 6 109 96 0.7
Without fertigation
Soil Depth NO3-N NH4-N Bray-P K Soluble Salts
Inches ----------- lb/A ----------- --------- ppm ---------- mmhos/cm
0-6 78 8 160 101 0.9
6-12 30 6 134 73 0.5
© 2009 Regents of the University of Minnesota

18. Soil Amendments & Treatments
2009
 No amendments added before planting
 Two treatments (same as in 2009)
 Fertigation
 UAN, Potassium nitrate and Calcium nitrate
 No fertigation
 Tomato and cucumber evaluated
 Two replications for tomato; one rep for cucumber
 Nine plants per replication
© 2009 Regents of the University of Minnesota

19. Procedures - 2009
 ‘Cobra’ tomato and ‘Sweet Success’ cucumber
 Transplants planted May 7
 Double row beds 4 ft apart; 2 ft between
plants for tomato and 18” apart for cucumbers
 One cup 20-20-20 (1 oz/gal) applied to each
transplant
 Plants pruned periodically
 Cucumbers harvested June 19 – October 8
 Tomatoes harvested July 30 – October 8
© 2009 Regents of the University of Minnesota

20. Not Fertigated
Fertigated
© 2009 Regents of the University of Minnesota

21. Not Fertigated
Fertigated
© 2009 Regents of the University of Minnesota

22. Fertigation Dates and Rates - 2009
Date Source oz N/100' lb N/A K2O/100' lb K2O/A
1-Jun 28% 0.48 3.2 0 0
8-Jun 28%+Knit 0.72 4.9 1.5 10.2
15-Jun 28%+Knit 0.72 4.9 1.5 10.2
24-Jun 28%+Knit 0.72 4.9 1.5 10.2
1-Jul 28%+Knit 0.82 5.6 2 13.6
8-Jul Knit+CaNit 1.03 7 2 13.6
15-Jul Knit+CaNit 1.03 7 2 13.6
23-Jul Knit+CaNit 1.03 7 2 13.6
29-Jul Knit+CaNit 1.03 7 2 13.6
5-Aug Knit+CaNit 1.03 7 2 13.6
12-Aug Knit+CaNit 1.03 7 2 13.6
19-Aug Knit+CaNit 1.03 7 2 13.6
27-Aug Knit+CaNit 1.03 7 2 13.6
2-Sep Knit+CaNit 1.03 7 2 13.6
9-Sep Knit+CaNit 1.03 7 2 13.6
17-Sep Knit+CaNit 1.03 7 2 13.6
25-Sep Knit+CaNit 1.03 7 2 13.6
Total © 2009 Regents of the University of
15.8 Minnesota
107.5 30.5 207.4

23. Tomato Early Yields 2009
- First 3 Weeks-
Treatment fruit number/plant fruit wt. (lbs/plant)
Fertigated 5.9 + 0.5 2.3 + 0.3
Non-fertigated 4.8 + 0.7 2.1 + 0.3
 Slight increase with fertigation
© 2009 Regents of the University of Minnesota

24. Marketable Tomato Yields – 2009
Treatment fruit number/plant fruit wt. (lbs/plant)
Fertigated 33.1 + 1.5 12.8 + 0.8
Non-fertigated 31.6 + 1.9 13.0 + 0.3
Non-fertigated as good or
better than fertigated
© 2009 Regents of the University of Minnesota

25. Marketable Cucumber Yields – 2009
Treatment fruit number/plant fruit wt. (lbs/plant)
Fertigated 22.5 36.4
Non-fertigated 22.7 37.3
Non-fertigated as good or
better than fertigated
Is compost the only source
of nutrients???
© 2009 Regents of the University of Minnesota

26. What’s in the Water???
Sample pH EC Nitrate-N Ammonium-N P K
mmhos/cm --------------------- ppm ---------------------
Irrigation Water 8.2 61 24 <1 <1 2
Fertigation water 8.2 85 56 5 <1 79
Water without fertigation 8.4 61 25 <1 <1 1
Water after fertigation 8.2 61 25 <1 <1 2
24 ppm nitrate-N in irrigation water
0.67 gal/min/100 sq. ft.
1 hour per irrigation & 96 irrigation events
~ 85 lb N/A
© 2009 Regents of the University of Minnesota

27. Soil Test after Final Harvest
– October 2009
With fertigation
Soil Depth NO3-N NH4-N Bray-P K Soluble Salts
Inches ----------- lb/A ----------- --------- ppm ---------- mmhos/cm
0-6 47 6 148 110 0.5
6-12 32 4 132 82 0.4
Without fertigation
Soil Depth NO3-N NH4-N Bray-P K Soluble Salts
Inches ----------- lb/A ----------- --------- ppm ---------- mmhos/cm
0-6 24 5 127 44 0.4
6-12 17 5 132 48 0.3
© 2009 Regents of the University of Minnesota

28. Summary
 Compost applied at high rates
before planting can reduce or
eliminate the need for fertigation
 Lack of response to fertigation in
this study was also in part due to
high nitrate in irrigation water
 Soil tests at harvest suggest that
potassium will be limiting in the
nonfertigated treatment next
year © 2009 Regents of the University of Minnesota