Soil Fertility Research in High Tunnels

Carl Rosen, Terry Nennich, & Jerry Wright University of Minnesota

High Tunnel WorkshopAlexandria, MN

December 2-3, 2009© 2009 Regents of the University of Minnesota

Topics

Background (review)

Fertigation study – Tomato 2008 and 2009 Cucumber 2009 (spidermite problem in 2008)

Compost vs. compost + fertigation

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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

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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/A40 lbs P/A (92 lbs P2O5)

470 lbs K/A (564 lbs K2O)© 2009 Regents of the University of Minnesota

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 2008 & 2009© 2009 Regents of the University of Minnesota

Staples High Tunnel

20’ wide x 48’ length

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Soil Test Properties in the Spring-2008 (before compost application)

P was in the very high range, K was medium

Soil Depth pH Organic Matter Soluble SaltsInches % mmhos/cm

0-6 7.0 6.4 0.96-12 6.9 5.4 0.7

Soil Depth NO3-N Bray-P KInches lb/A

0-6 61 174 896-12 43 144 103

--------- ppm ----------

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Soil Amendments & Treatments2008

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 plants per replication© 2009 Regents of the University of Minnesota

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

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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

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Fertigated

Not Fertigated

Staples High Tunnel in 2008

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Fertigation Dates and Rates - 2008Date 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 12.7 86.5 24.5 166.6© 2009 Regents of the University of Minnesota

Tomato Early Yields 2008 - First 3 Weeks-

Fertigation tended to delay yield

Treatment fruit number/plant fruit wt (lbs/plant)Fertigated 7.5 ± 0.9 2.5 ± 0.3Non-fertigated 8.8 ± 0.0 3.3 ± 0.1

Marketable

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Marketable Tomato Yields - 2008

Non-fertigated as good or better than fertigated

Compost supplied enough nutrients

Treatment fruit number/plant fruit wt. (lbs/plant)Fertigated 27.5 + 0.3 10.1 + 0.3Non-fertigated 29.9 + 3.1 13.2 + 1.1

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Soil Test after Final Harvest – Fall 2008

With fertigationSoil Depth NO3-N Bray-P K Soluble Salts

Inches lb/A mmhos/cm0-6 50 181 117 0.4

6-12 37 161 101 0.4

Without fertigationSoil Depth NO3-N Bray-P K Soluble Salts

Inches lb/A mmhos/cm0-6 36 193 76 0.4

6-12 26 145 75 0.3

--------- ppm ----------

--------- ppm ----------

© 2009 Regents of the University of Minnesota

© 2009 Regents of the University of Minnesota

Soil Test before Planting – April 2009

With fertigation

Without fertigation

Soil Depth NO3-N NH4-N Bray-P K Soluble SaltsInches mmhos/cm

0-6 84 10 167 146 0.86-12 44 6 109 96 0.7

----------- lb/A ----------- --------- ppm ----------

Soil Depth NO3-N NH4-N Bray-P K Soluble SaltsInches mmhos/cm

0-6 78 8 160 101 0.96-12 30 6 134 73 0.5

--------- ppm --------------------- lb/A -----------

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Soil Amendments & Treatments2009

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

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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

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Fertigated

Not Fertigated

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Not Fertigated

Fertigated

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Fertigation Dates and Rates - 2009Date Source oz N/100' lb N/A

K2O/100' lb K2O/A

1-Jun 28% 0.48 3.2 0 08-Jun 28%+Knit 0.72 4.9 1.5 10.2

15-Jun 28%+Knit 0.72 4.9 1.5 10.224-Jun 28%+Knit 0.72 4.9 1.5 10.21-Jul 28%+Knit 0.82 5.6 2 13.68-Jul Knit+CaNit 1.03 7 2 13.6

15-Jul Knit+CaNit 1.03 7 2 13.623-Jul Knit+CaNit 1.03 7 2 13.629-Jul Knit+CaNit 1.03 7 2 13.65-Aug Knit+CaNit 1.03 7 2 13.612-Aug Knit+CaNit 1.03 7 2 13.619-Aug Knit+CaNit 1.03 7 2 13.627-Aug Knit+CaNit 1.03 7 2 13.62-Sep Knit+CaNit 1.03 7 2 13.69-Sep Knit+CaNit 1.03 7 2 13.617-Sep Knit+CaNit 1.03 7 2 13.625-Sep Knit+CaNit 1.03 7 2 13.6Total 15.8 107.5 30.5 207.4© 2009 Regents of the University of Minnesota

Tomato Early Yields 2009 - First 3 Weeks-

Slight increase with fertigation

Treatment fruit number/plant fruit wt. (lbs/plant)Fertigated 5.9 + 0.5 2.3 + 0.3Non-fertigated 4.8 + 0.7 2.1 + 0.3

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Marketable Tomato Yields – 2009

Non-fertigated as good or better than fertigated

Treatment fruit number/plant fruit wt. (lbs/plant)Fertigated 33.1 + 1.5 12.8 + 0.8Non-fertigated 31.6 + 1.9 13.0 + 0.3

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Marketable Cucumber Yields – 2009

Non-fertigated as good or better than fertigated

Is compost the only source of nutrients???

Treatment fruit number/plant fruit wt. (lbs/plant)Fertigated 22.5 36.4Non-fertigated 22.7 37.3

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What’s in the Water???

Sample pH EC Nitrate-N Ammonium-N P Kmmhos/cm

Irrigation Water 8.2 61 24 <1 <1 2Fertigation water 8.2 85 56 5 <1 79Water without fertigation 8.4 61 25 <1 <1 1Water after fertigation 8.2 61 25 <1 <1 2

--------------------- ppm ---------------------

24 ppm nitrate-N in irrigation water0.67 gal/min/100 sq. ft.1 hour per irrigation & 96 irrigation events~ 85 lb N/A

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Soil Test after Final Harvest – October 2009

With fertigation

Without fertigation

Soil Depth NO3-N NH4-N Bray-P K Soluble SaltsInches mmhos/cm

0-6 47 6 148 110 0.56-12 32 4 132 82 0.4

--------- ppm --------------------- lb/A -----------

Soil Depth NO3-N NH4-N Bray-P K Soluble SaltsInches mmhos/cm

0-6 24 5 127 44 0.46-12 17 5 132 48 0.3

--------- ppm --------------------- lb/A -----------

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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