Managing and Amending Soils for Productive Yields in High Tunnels, 2015

Managing and
Amending Soils for
Productive Yields
in High Tunnels
Terrance T. Nennich, Fruit and
Vegetable Production
Carl Rosen, Dept of Soil Water and
Climate

2
© 2012 Regents of the University of Minnesota. All rights reserved.
TOPICS
 Considerations before planting
– Site selection
 Yield potential in a high tunnel
– Satisfying nutrient needs
 Preplant amendments
– Importance of soil testing
 Nutrient management
– Without fertigation
 Nutrient sources – organic and controlled release
– With fertigation
 Nutrient sources & timing of application

3
SITE SELECTION
 Ideal soil is a well-drained sandy loam to silt
loam
 Medium to high organic matter levels (3.5 to
6%)
 Consider growing green manure crops before
planting/establishing the tunnel
– Sorgum-sudan
– Rye or oats
– Legumes such as field peas, clover

4
IMPROVING SOIL PHYSICAL
PROPERTIES
 Compost addition
– 1-2 lbs compost per
sq. ft.
 Use good quality
compost
– Beware of herbicide
residuals

5
YIELD POTENTIAL & NUTRIENT NEEDS
 Yields in a high tunnel can be 2 to
4 times the yield obtained in the
field
 Higher yields will require 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

6
CROPS THAT DEMAND HIGH
FERTILIITY
Tomatoes
Cucumbers
Egg Plants
Okra
Peppers

7
CROPS THAT USE MEDIUM
FERTILITY Strawberries
 Raspberries
 Fruit Trees
 Beans
 Potatoes ??
 Carrots

8
LOW FERTILITY CROPS
 Lettuce
 Spinach
 Greens
 Beans
 Some cole crops

9
PUTTING A HIGH TUNNEL IN
PERSPECTIVE
 1 acre = 43560 sq ft.
 A 26 X 96 High Tunnel = 2496 sq/ft
 26 X 96 High tunnel = .057 acres
 A little over 1/20th
of a acre.
 So when a soil tests requires 300 pounds of
Nitrogen for Example
 300 X .057 = 17 pounds of N applied in the
high tunnel

10
SOIL FERTILITY
Start with a complete
soil test
 $Cost is about 35.00
 Bring soil to high level

11
SOIL FERTILITY
 If soil fertility is low from the beginning you
will not work your way out.
 If you are planting a crop in rows test the
rows
 We blame it on Potassium

12
FERTILIZER PLACEMENT
 It is important to keep the high tunnel
fertility to a high level through out the high
tunnel
 But—
 In high tunnels the fertilizer extraction
zone is very narrow as compared to field
production
 12- 16 inches as compared to 36 inches +
in the field

13

15
TOMATO FERTILITY DEMANDS IN
HIGH TUNNELS
 Not hard to get 5-7 pounds per plant
 Usually enough fertility in soil with a little
extra compost
 20 pounds per plant excellent fertility
 25- 50 pounds per plant requires
extremely high fertility, supplied at the
proper stages of growth in proper
amounts.

16
“Book Values” for Tomatoes
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)

17
Tomato Fertilizer Use 5lb Plant
N P K
Fruit 3.4 0.4 6.0
Vines 2.6 0.4 3.4
Total 6.0 0.8 9.4
Field Production 13.5 ton: ( 5 Lbs
Plant)
81 lbs N/A
11 lbs P/A (25.3 lbs P2O5)

18
N P K
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: ( 20 Lbs
Plant)
300 lbs N/A

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N P K
Fruit 3.4 0.4 6.0
Vines 2.6 0.4 3.4
Total 6.0 0.8 9.4
A 100 ton yield/A would require: ( 40 Lbs
Plant)
600 lbs N/A
940 lbs K/A (1128 lbs K2O)

20
SATISFYING NUTRIENT DEMAND IN A
HIGH TUNNEL SYSTEM
 Release of nutrients from the soil
– Importance of good preparation
 Addition of fertilizer
– Preplant
– During the growing season
 fertigation

21
AMENDMENTS BEFORE PLANTING
 Have soil tested before
applying amendments
– pH, OM, nitrate-N, P, K,
Ca, Mg, micronutrients,
soluble salts
– Retest yearly, especially
if problems are occurring

22
SOLUBLE SALTS (EC)
 Based on saturated paste:
– < 2 mmhos/cm (dS/m) - no
problems
– 3-4 some plants affected
– 5-7 many plants affected
– >8 only salt tolerant plants
survive
 Most soils in Minnesota have
low salts, but salts may
accumulate with excessive
fertigation

23
SOIL PH
 Acceptable range: 5.5-7.5
 Adjust before planting
– Acid soils – use calcitic or dolomitic
limestone
– Alkaline soils – use compost, sphagnum
peat, elemental sulfur

24
PHOSPHORUS AND MICRONUTRIENTS
 Base P application on soil test level
– Greater than 41 ppm is considered very high for most
vegetables/fruit
 Incorporate before planting if soil test indicates a need
– Potassium phosphate, DAP, MAP
– Numerous micronutrient sources
– Composted manure
 Use starter solutions high in P for transplants

25
NITROGEN AND POTASSIUM
 A portion should be applied before planting
 Base K fertilizer application on soil test – most can be applied preplant
– Greater than160 ppm is considered very high for most vegetables/fruit
– potassium chloride (0-0-60)
– potassium sulfate (0-0-50)
– potassium magnesium sulfate (0-0-22); acceptable organic source
 For soluble N sources, apply about 1/3 – 1/2 of the required N before
planting
– urea (46-0-0)
– ammonium nitrate (34-0-0)
– calcium nitrate (15.5-0-0)
– potassium nitrate (13-0-44)
– composted manure (variable)

26
NUTRIENT MANAGEMENT
WITHOUT FERTIGATION
 Organic systems
 Type of compost
 Moisture content
 Crops grown
– To supply equivalent of 100 lbs available N/A:
 Dairy manure compost: 2700 lbs/1000 sq. ft.
 Poultry manure compost: 900 lbs/1000 sq. ft.
– Incorporate 6 to 8 inches into soil

27
NUTRIENT MANAGEMENT
WITHOUT FERTIGATION
– Use legume cover
crops
– Warm season cover
crops can be planted
later in the season

28
NUTRIENT MANAGEMENT
WITHOUT FERTIGATION
 Conventional system
– Soluble fertilizers
– Controlled release N fertilizers
 Coated urea
 Osmocote
 Be sure that release rate is fast enough for the crop
being grown
– For most vegetables – 50 to 70 day release is needed
– Temperatures are warmer in a high tunnel – faster release

29
NUTRIENT MANAGEMENT
WITH FERTIGATION
 Injection of one or more nutrients into the irrigation
water
 Review the Minnesota Chemigation/Fertigation
Permit Application and Safety Requirements
– www.mda.state.mn.us
 Submit the Minnesota Chemigation/Fertigation
Permit Application to MDA
– Main requirement is to have recommended anti-pollution
and safety devices

30
NUTRIENT MANAGEMENT
WITH FERTIGATION
 Primarily used for nitrogen and
potassium
– Urea-ammonium nitrate (28%N) (liquid)
– Calcium nitrate (15.5% N)
– Potassium nitrate (13% N; 44% K2O)
– Potassium chloride (60%; K2O)
– Blends eg. 20-20-20
 Soluble sources of organic fertilizers
are available, but are expensive and
may cause clogging
– Some fish emulsions have been
successfully used

31
Solubility of Common Fertilizers
Material Composition Salt index
Solubility
% N %P2O5 %K2O lbs/gal H20
Calcium nitrate1
15.5 0 0 53 8.5
Potassium nitrate 13.0 0 44 73 1.1
Ammonium nitrate 33.5 0 0 105 9.8
Urea 46.0 0 0 75 6.5
Ammonium sulfate2
21.0 0 0 69 5.9
Potassium chloride 0.0 0 60 116 2.3
Potassium sulfate2
0.0 0 50 46 0.6
Diammonium phosphate2
18.0 46 0 30 3.6
1
May cause clogging if irrigation water is high in bicarbonates
2
Not recommended for use with calcium nitrate or if irrigation water is high in calcium

32
MIXES TO AVOID
 Phosphorus compounds with calcium or iron
 Calcium with sulfate and bicarbonate
 To avoid precipitation problems two stock tanks
should be used, one for calcium nitrate and iron
chelate and the other for the remaining fertilizers
– Alternatively apply P fertilizer preplant

33
RATE AND TIMING OF
APPLICATION
 Preparing soils and applying preplant nutrients is
still important - compost or fertilizer
 About 1/2 of N and K needs can be applied
through fertigation
 Timing is not as critical as rate
– Once per month
– Once per week
– Every time there is an irrigation event

34
FERTIGATION
 Use a batch loading fertigation approach
 Inject total volume of nutrient during an irrigation event
 Total volume of fertilizer for batch loading depends on the
area of the irrigated zone and the desired nutrient rate
 The injection rate does not need to be precisely controlled
 The injector should apply the chemical solution in a time
period that does not result in over-irrigation, otherwise
leaching will occur

35
Meeting the Demands for Crops
with Different Requirements
 Fertigate crops at different
times
– Allows for varying rates to be
applied
 Fertigate to meet the
demands of the crop
needing the lowest amount
of nutrients
– Make up difference with
preplant fertilizer

36
DETERMINING THE RATE OF N AND K
TO APPLY
 Most conventional
recommendations are
based on lbs N or K2O/A
 Ounces per linear feet of
row is more practical for
high tunnels
– Based on 4ft spacing
between rows
– 100 linear ft = 400 sq. ft.

37
TISSUE TESTING
 Plant tissue analysis at first flower.
 Tissue analysis:
– 10-15 whole leaves
– Collect from average plants
– Collect 4-5th
leaf from top
 Most recent mature leaf
– Paper bags only!
– Overnight or pickup

39
FOLIAR SPRAYS
 Foliar sprays will help, but it is difficult to
raise the potassium levels 2-4% points as
would be needed. Boron also plays a role
in helping with the uptake of K, Ca, sulfur
and Mg.
 More research needs to be done with this.

40
FERTILIZER
 Needs to be added at least weekly
 Up to Flowering 1-1-1 ratio
 After flowering 2 -1- 2 ratio
 Possible 1-1-4 after harvest.
 Added fertilizer should have Micro
Nutrients.

41
N and K Fertigation Schedule for
Tomatoes - lb/A basis
Days after Planting Daily N Weekly N Seasonal N Daily K2O Weekly K2O Seasonal K2O
----------------------------------------- lb/A--- ----------------------------------------------
Preplant ---- ---- 50.0 ---- ----- 100.0
0- 21 0.5 3.5 61.5 1.0 7.0 121.0
22- 49 0.7 4.9 81.1 1.4 9.8 160.2
50- 70 1.0 7.0 102.1 2.0 14.0 202.2
71- 91 1.1 7.7 125.2 2.2 15.4 248.4
92-112 1.0 7.0 146.2 2.0 14.0 290.4

42
N and K Fertigation Schedule for
Tomatoes – oz per 100 ft basis
Days after Planting Daily N Weekly N Seasonal N Daily K2O Weekly K2O Seasonal K2O
--------------------------------- oz/100 linear row ft --------------------------------------
Preplant ---- ---- 7.3 ---- ----- 14.7
0- 21 0.07 0.50 9.0 0.15 1.1 17.8
22- 49 0.10 0.70 11.9 0.21 1.5 23.5
50- 70 0.15 1.05 15.0 0.29 2.0 29.7
71- 91 0.16 1.12 18.4 0.32 2.2 36.5
92-112 0.15 1.05 21.5 0.29 2.0 42.6
1
assumes 4 ft spacing between rows; lb/A X 0.147 = oz/100 linear ft of row.
lbs/A x 0.147 = oz/100 linear ft of row

43
CALCULATING THE RATE OF
FERTILIZER TO INJECT
 Example for urea-ammonium nitrate (28%)
– Area to fertilize – 200 linear feet (800 sq. ft.)
– Liquid (28% N) – 3 lbs N/gallon
– Recommendation is 10 lbs N/A
– 10/3 = 3.33 gallons/A
– 3.33 gal * 800/43560 * 128 oz/gal = 7.8 fl oz
 Use similar approach for granular except
conversion to lbs product rather than fl. oz. is
made

44
Amount of UAN Solution for Various N
Rates per Acre
N Rates
lbs/ac
1 2 3 4 6 8 10
28%
Gallons/ac
0.33 0.67 1.00 1.33 2.00 2.67 3.33
28% fl. oz/100
linear ft of
row1
0.39 0.78 1.16 1.55 2.32 3.10 3.88
1
Assumes a between row spacing of 4 ft.

45
SUMMARY
 Soil test before planting
 Incorporate compost if needed to improve soil physical
and chemical properties
 If needed adjust acid soil pH with lime
 Incorporate P and micronutrients before planting based
on a soil test
 For organic production use composted manure before
planting

46
SUMMARY
 For conventional systems, use fertigation
with soluble N and K sources or use
controlled release fertilizers
 A portion of the N and K can be applied
before planting
 Total rate applied is more important than
timing
 Use the tables provided to estimate
amounts of nutrient required on a linear
foot basis

Managing and Amending Soils for Productive Yields in High Tunnels, 2015

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