Instructional Plan
Instructor:
Unit: High Tunnel Fruit and Vegetable Production
Greenhouse Operation and Management #18 - Describe the principles and techniques for
Competency: proper fertilization of [high tunnel] crops.
Lesson 5 Title: High Tunnel Soil Management and Fertility
Estimated Time: 2 50-minute class periods
Objectives/Study Questions
At the conclusion of this lesson, students will be able to:
 Recall soil’s physical and chemical properties and how they affect nutrient management.
 Calculate the fertilizer needs in a high tunnel based on soil test recommendations
 Identify characteristics of compost and what affects the decomposition rate.
 Recognize salinity issues associated with high tunnel production.
Materials, Supplies, Equipment, References, and Other Resources:
Materials/Supplies/Equipment:
 PowerPoint – Lesson 5: Soil Management and Fertility
 Chalk Board/White Board
 H.O. – High Tunnel Manual Appendix A1 – Compost Application Problem (pg. 99)
 1 Copy High Tunnel Manual Appendix B – Worksheet Answers (pg. 105)
 H.O. – High Tunnel Manual Appendix A2 – Inorganic Fertilizer Application Worksheet (pg. 100)
 1 Copy High Tunnel Manual Appendix B – Inorganic Fertilizer Application Worksheet (pg. 106)
References and Other Resources:
 High Tunnel Manual
 Brady, N.C., & Weil, R.R. (2008). The nature and properties of soils. Prentice-Hall, Upper Saddle, NJ.
 Taber, H.G. (2005). Garden soil management. Iowa State University Extension. Pm-820. Available
online at: http://www.extension.iastate.edu/publications/PM820.pdf
 Taber, H.G. (2005). Micronutrient characteristics with emphasis on vegetable crops. Iowa State
University Extension Publication FG-605. Available online at:
http://www.public.iastate.edu/~taber/Extension/Micronutrients%20.pdf
 Hightunnels.org - http://www.hightunnels.org/foreducators.htm
Interest Approach (Motivation):
*Note: It is assumed that students have existing knowledge on soil properties from prior lessons in biology and
prior agriculture courses. For this reason, the beginning of this lesson (Objective 1) is designed as a review.
SLIDE 1
You have learned about soils in many other places before, like in other Ag courses and in Biology.
 What can you tell me about what you know about soils?
 Why do you think soils would be important to discuss when we’re talking about high tunnels?
 Think about all you know so far about growing in a high tunnel. How would caring for the soil be
different in a high tunnel than in growing in a garden or field?
Communicate Objectives, Define Problem or Decision to be Made, or Identify Questions to Investigate:
Often, high tunnels are constructed and left in one place for a few growing seasons. Some high tunnels are
moveable, but many are not. This means that the same soil is used over and over. Rain can’t get to it because
we’re watering it from under the ground or right at the soil surface. This means we have to take very good care
of the soil we have, and amend it when necessary. Frequent soil test reports are necessary so that we know the
nutrient values within our soils.
SLIDE 2
In this lesson, we have four objectives:
 Recall soil’s physical and chemical properties and how they affect nutrient management.
 Calculate the fertilizer needs in a high tunnel based on soil test recommendations
 Identify characteristics of compost and what affects the decomposition rate.
 Recognize salinity issues associated with high tunnel production.
Instructor Directions / Materials
Content Outline, Instructional Procedures, and/or Key Questions
As we’ve already learned, selecting the site location is a key component for
Objective One
high tunnel vegetable production. When selecting the site, one must
Recall soil’s physical and
chemical properties and how they consider:
affect nutrient management.
 Sunlight
 Drainage and
 Wind protection
SLIDE 3
SLIDE 4
Soil type where we place the high tunnel is really not as important as those
three things. Why do you think that is?
 Soil type is less important because crops can be grown in modified
raised beds or in soilless media if amending the soil is needed.
 For the purposes of this lesson, let’s imagine our high tunnel is
moveable and therefore soil is a key consideration in determining
where to place the tunnel.
We’ve learned in other classes why soil is important and what purpose it
serves. Just to review, soil helps to:
 Anchor plants in place
 Provides (serves as the medium) for water and some needed plant
nutrients and also
 Provides oxygen for root growth.
The major components of soil, as you probably already knew, are the
physical properties, the chemical properties, and air and water. We’ll review
the physical and chemical properties in a little more detail.
Physical Properties
The physical properties of soil include the individual particles, particle size
(which is known as texture) and arrangement (known as structure) and the
organic matter that serves as the “glue” that holds the particles together.
SLIDE 5
Who knows what is meant by ‘soil texture’?
What are the three different soil textures?
The soil texture, or particle size, refers to the content of sand, silt and clay.
 As far as soil texture is concerned, the organic matter and gravel
content is ignored.
 Let’s look at why texture is important by examining the
characteristics of soils with different textures.
First, let’s look at the characteristics of soils with a high clay content:
 These soils have a high water-holding ability.
Instructor Directions / Materials
Content Outline, Instructional Procedures, and/or Key Questions
 Clay soils have a high cation exchange capacity, which means that it
is better at holding nutrients such as Ca, K, Mg, and micronutrients.
 Clay soils have a low infiltration rate, meaning it takes longer for
water to run down into these soils than soils with other textures. This
means that rain or overhead irrigation water often runs off before it
has the time to penetrate the soil.
 These soils warm up a lot more slowly in the spring.
 Clay soils also reset changes to pH, which means if liming is needed
to alter the pH of the soil, it will take more lime to make a change.
This is known as high buffering capacity.
Now that we’ve examined clay soils, we’ll look at the characteristics of high
sand content soils:
 Sandy soils have a low water-holding capacity, which means that water
runs through them very quickly. They cannot hold water around the
roots as long for uptake into plants.
 Some nutrients are prone to leaching in sandy soils.
 These soils tend to warm up quickly in the spring.
 Sandy soils tend to show a rapid change in pH, so this has to be
monitored closely.
SLIDE 6
Because of its characteristics, a soil test is needed about every 1 to 2 years
for a sand or sandy loam soil, but only every 4 years is necessary for a soil
with higher clay content.
From a soil standpoint, good locations for high tunnels consist of:
 Well-drained, loam soils with high organic matter (greater than 3%).
- Ideally, these loam soils should be less than 28% clay.
- Silt loams are also acceptable.
 Soil pH should be 6.5 on the upper part of the landscape.
 A northwest windbreak is also ideal.
- We’ll talk a little bit later about how pH can be adjusted. This
includes the use of agricultural limestone and adding compost to
improve organic matter content.
SLIDE 7
Chemical Properties (Plant Nutrients)
 Only 17 elements are needed by plants to achieve top production and
fruit quality.
- Three of these essential elements are provided by the air and
water and are never limiting, meaning they are always in
abundant supply. These three elements are carbon (C), hydrogen
(H), and oxygen (O).
- The remaining 14 elements may or may not be in adequate
amounts depending on soil type and pH.
 As you probably know, pH is potential acidity of the soil.
- Neutral pH is 7.0. A soil pH above 7.0 is alkaline, or basic. When
the pH is below 7.0, the soil is acidic.
 Generally, vegetables do well in slightly acid soils (pH of 6.2 to 6.8).
Instructor Directions / Materials
Content Outline, Instructional Procedures, and/or Key Questions
- This is because in this range, root growth, plant vigor, nutrient
availability, and microbial activity are optimal.
- Beyond this range, on either side, plant growth can be severely
limited because the required nutrients are unavailable and soil
microbes work less effectively.
 Soil tests and plant analyses can determine if the levels of essential
nutrients are adequate, or if work to amend the soil or alter the pH is
needed.
- Nitrogen (N), Phosphorus (P), and Potassium (K) are the nutrients
we usually have to worry about the most. They can be added to
the soil with commercial fertilizers or compost.
- Calcium (Ca) and Magnesium (Mg) are usually not a problem in
Midwest soils. They may leach out of sandy soils, but can be
replaced with lime applications.
- Sulfer (S), Nickel(Ni), and Chlorine (Cl) are naturally available
nutrients through organic matter.
Objective Two
Calculate the fertilizer needs in a
high tunnel based on soil test
recommendations.


SLIDE 8
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
SLIDE 9

An adequate soil pH is one of the most important soil amendment
factors necessary for healthy plant growth.
- As mentioned earlier, most vegetables do well at a pH range of
6.2 to 6.8, but some crops can stretch the range from 5.7 to 7.4.
- Nonetheless, you will derive more beneficial effect from
improving pH, if low, to 6.5 than adding other fertilizer elements.
- Low pH occurs where heavy N rates have been used in the past
and/or on sandy loam or coarser textured soils where the bases,
such as Mg, Ca, and K, have been leached.
If the pH of a soil is too low and needs to be increased, this can be
done through amendments, most commonly agricultural lime.
Increasing the soil pH means reducing the acidity.
There are several potential sources of lime.
- First is ground limestone, which makes up 95% of liming
materials. The two types of ground limestone most commonly
used are calcite and dolomitic lime. Calcite is used with
Magnesium (Mg) is low to medium, and dolomitic lime is used
when Mg is high (greater than 10%).
- Other sources of lime include calcium oxide and calcium
hydroxide. Both are quick reacting. Calcium oxide is distributed
in lumps, calcium hydroxide is a hydrated solution.
When liming, it is important to always use agricultural limestone.
State law requires this certification based on the effective calcium
carbonate equivalency and fineness of the limestone used.
- It is best to apply limestone well in advance of the growing
season, typically in the fall before the tunnel is constructed on the
site.
- If you find that the pH is low just prior to planting in the spring,
consider using the hydrated or slaked lime for a quick reaction.
These products can be obtained from most lumber companies.
When amending soil through the use of lime, it is very important not
to over apply. Over application of liming can have detrimental
effects including:
Instructor Directions / Materials
Content Outline, Instructional Procedures, and/or Key Questions
- Dramatic change in pH, which is detrimental to plant growth.
- Decrease in availability of P.
- Deficiencies in Fe, Mn, Zn and, to some extent, Cu.
- Reduced root uptake of B.


SLIDE 10



SLIDE 11


In addition to altering soil pH, amending the soil with fertilizers and
replenishing nutrients may be needed.
In most soil tests in Missouri, Nitrogen is usually not reported on soil
tests because we have higher rainfall and unpredictable rain events.
This often makes a soil Nitrogen test meaningless because it is
highly leachable.
- For growing in a high tunnel, growers may request that Nitrogen
be included on their soil test reports. This is because a high tunnel
creates desert-like conditions, blocking the soil from rain fall.
When making a decision on a fertilizer to purchase, it is very
important that you do not purchase more fertilizer than needed. This
can be costly and is unnecessary.
- For this reason, we must know how to calculate our fertilizer
needs based on the information we receive from our soil test
reports.
- Who knows what the most common nutrients provided by
fertilizer are? (Nitrogen, Phosphorus, Potassium)
 Always listed in that order on a bag of fertilizer – N-P-K.
We must always determine the amount of fertilizer we need based on
the recommendations of our soil test. Why? What might happen if
we just guess at the amounts needed?
Most recommendations are given in pounds per acre.
- Because you will need to know it to calculate the amount of
fertilizer needed, you need to memorize that there are 43,560
square feet in an acre.
If a grower chooses to apply compost (liquid or dry) to high tunnel
soil, they will also need to know the following figures:
- 1 cubic yard = 182 gallons
- 1 inch of surface compost over 1,000 feet squared equals 3.1
cubic yards
- An analysis of the compost must be done so that accurate
calculations can be made and the application amount will be
correct.
To accurately calculate the amount of fertilizer needed for a high
tunnel, the dimensions of the high tunnel must also be known.
Let’s do a few practice problems in calculating application rates. You will
need to know how to do this for your assignment at the end of the lesson.
SLIDE 12
Practice Problem 1
 Your soil test recommends applying 1 lb of Nitrogen for every 1,000
square feet.
 You have chosen to utilize a 24-4-12 pre-mix fertilizer.
Instructor Directions / Materials
SLIDE 13
Content Outline, Instructional Procedures, and/or Key Questions
- This means that the mix is 24% Nitrogen, 4% Phosphorus, and
12% Potassium.
 Your high tunnel is 24 feet wide by 48 feet long.
 How much Nitrogen do you need to apply to the soil in your high
tunnel?
- First, we must determine how many pounds of the mix we should
use to reach the 1lb/1000 square foot recommendations. Do this
we take the divide the lbs recommended per square feet by the
percent of the needed nutrient in the mix. So: 1 lb/1,000 ft2 / .24 =
4.16 lb Nitrogen/1000 ft2
- Second, we need to determine the square feet of our high tunnel:
24 x 48 = 1,152 ft2 / 1000
- Our recommendation is based on 1000 square feet, but our high
tunnel is not exactly 1000 square feet, so this number must be
adjusted. To do this, we divide our square footage by 1000:
1,152/1000 = 1.152. This means that our high tunnel is 1.152 of
the recommendation based on 1000 square feet.
- Our final step is to adjust our recommended application amount
(which is the number of pounds based on 1000 square feet we
found earlier) by the square footage of our high tunnel to
determine exactly how much of the pre-mix fertilizer we should
apply to achieve 1lb/1000 square feet. We multiply 4.16 (found
earlier) by our adjusted size of high tunnel which is 1.152. So:
4.16 lbs x 1.152 = 4.79 lbs of the premix fertilizer need to
applied to the high tunnel soil in order to reach the
recommended 1lb N/1000 square feet.
Practice Problem 2
 Let’s try another problem for some practice.
 This soil test recommends that we apply 1.5 lbs of Potassium (K) per
1000 square feet.
 We have selected a 0-0-60 premix fertilizer to apply; this means the
mix has no nitrogen or phosphorus. What percentage of the bag mix
is K? (60%)
 Our high tunnel dimensions are 20 feet wide by 36 feet long.
 First, we divide the amount recommended by the percentage of the
nutrient in the mix.
1.5 lbs K/1000 ft2 /.60 = 2.5 lbs K /1000 ft2
 Second, we need to determine the square footage of our high tunnel.
20 x 36 = 720 ft2
 Third, we must divide our square footage by the square footage the
recommendation is based upon (1000).
720/1000 = .72
 Finally, we must multiply the pounds of mix needed to achieve
1.5lbs K/1000 square feet by the square footage adjustment for the
space of our high tunnel. This will tell us how much of the bag mix
we should apply to reach the recommended application rate.
2.5 lbs/.72 = 1.8 lbs of K
Instructor Directions / Materials
Content Outline, Instructional Procedures, and/or Key Questions
Practice Problem 3
If using organic compost as fertilizer, the compost must be analyzed for
nutrient content so that accurate applications can be made.
Given:
 Nitrogen recommendation is 60 lbs/acre.
 High tunnel is 21 feet wide and 96 feet long
 We know our formulations given earlier:
- 1 cubic yard = 182 gallons
Teachers Note: You will need to
- 1 inch of surface compost over 1000 square feet = 3.1yd3
hand out page 99 from the
- Because this compost is part liquid and part dry matter, these
manual to each student for this
formulas will be needed.
problem. Have page 105 (answer
sheet) handy to help walk the
1) How many gallons of compost do I need for the high tunnel?
students through the problem.
 Nitrogen = 1.4% on a dry weight basis. Only 63% solids, so 0.88%
This is optional. Students are
N on wet basis (1.4 × 0.63). But only 20% is available the first year.
asked to complete an inorganic
 The tunnel square feet = 21 × 96 = 2,016 square feet (SF)
problem for the assignment. This
Nitrogen rate = 60 pounds per acre and only 2,016 SF, so
practice problem is different
2,016/43,560 SF in an acre = 0.046 acres in the tunnel.
from the previous two and is
 Therefore, the amount of nitrogen needed is 60 × 0.046 = 2.76
based on utilizing compost
pounds
manure as a fertilizer in the high
 Using a general string formula:
tunnel.
4.85 pounds per gallon (bulk density of compost) × 0.63 (% solids)
× 0.14 (% nitrogen) × 0.2 (% nitrogen available first year) = 0.00856
pounds nitrogen per gallon available
2.76 pounds nitrogen needed
 2.76/0.00856 = 322.4 gallons compost to spread in the tunnel
SLIDE 14
2) What is the depth of the compost, in inches, over the surface
area?
Objective Three
Identify characteristics of
compost and what affects the
decomposition rate.
 Using what you know, the 322 gallons of compost = 322/182 gallons
per cubic yard = 1.78 cubic yards
 The number of 1,000 SF units in the tunnel = 2,016/1,000 = 2.016
1.78/2.016 = 0.88 cubic yards per 1,000 SF
 0.88/3.1 cubic yards per 1 inch = 0.29 inches or approximately 1/4 to
1/3 inch
3) What is the tons per acre equivalent?
 From question 1, we found that 322 gallons of compost are needed x
4.85 pounds per gallon = 1.562 pounds per 0.046 acres in tunnel
 1,562/0.046 = 33,957 pounds per acre or 33,957/2,000 =
approximately 17 tons per acre
 Organic matter is derived from the decomposition of organic
residues, often composted materials, and the excretions from
microorganisms and microbial cells that create that decomposition.
 The end product of this reaction is called hummus. This is the more
or less stable fraction of the soil organic matter remaining after the
major portion of the added plant and animal residues have
Instructor Directions / Materials
SLIDE 15
SLIDE 16
Content Outline, Instructional Procedures, and/or Key Questions
decomposed.
 The organic matter fraction of soil is small (1-6%) compared to the
clay content of soils.
 Three major reactions occur when fresh, organic tissue is added to a
well-aerated soil.
- First, carbon is oxidized by the small microorganisms to produce
carbon dioxide, energy and biomass (humus).
- Second, Nitrogen, Phosphorus, and Sulfur are release or
immobilized by the microbe population.
- Third, compounds that are very resistant to microbial action are
formed. Lignin is formed, for example, which is a very large
complex consisting of hundreds of inter-linked phenolic rings
with various methyl groups attached. They are difficult for the
microbes to breakdown.
The decomposition rate of organic matter depends on a number of
factors:
 Environmental conditions, such as moisture, temperature and soil
texture.
 Particle size of organic material. Smaller results in faster
decomposition because of more surface area (i.e., twigs versus
branches. Whole leaves versus grinding, which destroys the waxy
outer coating, breaks up the ligneous cell walls).
 Cultivation frequency. Cultivation disrupts soil aggregate structure.
 Depth of tillage. Tilling close to the soil surface results in slower
decomposition; Incorporated organic matter decomposes faster. (the
soil is moist and contains more soil microorganisms at a greater
depth).
 Irrigation. Good soil moisture favors rapid decomposition but also
increases production of dry matter.
 Type of organic matter. Materials rich in N, such as green and
animal manures, decompose more quickly.
 Crop rotation. An extensive root system has a higher C:N ratio.
Adding organic matter to the soil has many benefits, including:
 Provides a nutrient reservoir for N, P and S.
 Retains nutrients in an available form - humus molecules have pHdependent charges that hold positive ions.
 Increases aggregate formation - the crumb-like structure that gives
soil 'tilth', or the glue
 Increases soil porosity - changes the physical characteristics of the
soil; alters water retention and water infiltration.
SLIDE 17
A number of considerations should be made when adding organic
amendments to the soil:
 Organic materials are highly variable in composition and quality.
Instructor Directions / Materials
SLIDE 18
Content Outline, Instructional Procedures, and/or Key Questions
- The age and components within the organic matter directly
impact which nutrients and the amount of each nutrient is
available within the amendment.
- Nitrogen availability is of largest concern, because it must be
mineralized to the soluble form for plants. There is no accurate
formula or lab test to predict the rate of mineralization. The
availability of N declines as manure ages.
- Wetting, drying, rainfall and microbiological activity affect the
amount of inorganic N that is lost through leaching and
volatilization, and the remaining N that is stabilized in humuslike compounds.
- Nitrogen is more available in poultry manure than in horse, cow
or sheep because it contains uric acid. Also, other animals have
more roughage in the diet - N less readily decomposed due to
presence of lignin and cellulose.
 No standards for labeling organic soil amendments exist.
 Growers should be sure to analyze each load or shipment. It is
recommended that official analysis be conducted before any organic
matter is used.
 Organic amendments, or composts, are more expensive to transport,
store, purchase and apply.
 Some organic amendments or composts could contain sewage
sludge, which could have high levels of heavy metals.

SLIDE 19
Objective Four
Recognize salinity issues
associated with high tunnel
production.
SLIDE 20
As mentioned on the previous slide, growers should have a chemical
analysis conducted of any load or shipment of organic matter.
 According to the United States Composting Council (USCC),
compost chemical analysis should include:
- pH (look for 6.0 to 7.5).
- Ec (look for 5.0 or less). Plant tolerance to salinity varies widely.
- C:N ratio (recommend an initial of 30:1). Mature compost
should be between 10:1 to 15:1.
- Bulk density (solids/moisture content; expressed as lbs/yd3). It
is useful in determining rate of application.
Heavy metals – Zn, Cd, Cu, Ni, Pb, Hg, Mo, As, Cr, Co.
Overall nutrient profile – essential plant nutrients (N, P, K, etc)

When you think about salt buildup, or salinity, in a high tunnel,
why might this be a problem with high tunnels?
Salinity
 Salt buildup in high tunnel soils becomes a more prevalent issue
when the cover is left on year around.
 Whenever the plastic is to be changed, remove the old plastic and
leave it off as long as possible (e.g. through the winter) to get natural
leaching from rain and snow.
 As an additional method of reducing the problem, check the salt
level of irrigation water. If high, then finding an alternative irrigation
water source lower in salts could be considered within a few years,
before salt buildup becomes too great. Surface water sources could
Instructor Directions / Materials
Content Outline, Instructional Procedures, and/or Key Questions
be considered. Capturing rainfall from the roofs of structures can be
practical if the high tunnel is nearby buildings with gutters.

Why is soil salinity an issue? Symptoms of high soil salinity include:
- Root dieback, root tips burn off
- Plant stunting – all parts: leaves, stems, roots, fruits
- Leaf burn – edges, lower leaves
- Wilting – high osmotic pressure prevents uptake of water. This
is worse in hot, dry weather. Salinity sensitivity varies among
plant genera.

Why might high salinity (salt buildup) in the plant root zone of soils
occur? It may be due to a variety of factors:
- Poor placement of fertilizer - starter at planting, poor mixing in
pots, etc.
- Fertilizer salts mainly due to K and nitrate (but could be Na, Ca,
Mg, Cl, SO4).
- Evapotranspiration greater than irrigation.
- Too much fertilizer applied - excess of plants needs.
- High water table - evaporation from soil surface causes
groundwater to move up, carrying salts into the upper level.
SLIDE 21

When working to reduce high salt levels:
- Monitor soil salt levels with the Ec test during routine soil
sampling.
- Place tunnel on well-drained site, add tile line.
- Be careful with nutrient applications, do not over fertilize.
SLIDE 22
- Limit the use of organic sources containing animal manures.
- Keep sides rolled up in winter.
- Leach salt downward in the soil profile via irrigation. Generally,
for 1 foot of soil:
 6 inches of water will leach out 1/2 of the salt
 12 inches of water will leach out 4/5ths or 80 % of the salt
- Constant watering with trickle irrigation techniques moves salt
to the outer edge of the wetting zone & helps reduce symptoms.
In review,
Closure/Summary:
 Why is soil management and fertility important to growing produce
Ask as many of these review
in a high tunnel?
questions as you see fit or as time

What are the physical properties of soils?
allows. This is a good
 From the standpoint of soil physical properties, what is ideal for the
opportunity to clear up any
placement of a high tunnel?
questions students may have and
 How do soil chemical properties influence nutrient management?
identify areas of the content that
 Why is soil pH important to plant health? What is the ideal soil pH
may need further review or
for most vegetables?
explanation.
 What can be done to alter a soil’s pH or nutrient value?
 Why is it important to calculate application amounts instead of just
SLIDE 23
applying as you choose?
Instructor Directions / Materials
SLIDE 24
Application and Evaluation:
H.O. – Compost Application
Problem
H.O. – Inorganic Fertilizer
Application Worksheet
Content Outline, Instructional Procedures, and/or Key Questions
 What are some characteristics of compost, or organic matter?
 What influences the decomposition rate of compost?
 What are the benefits of adding organic matter to soil?
 What should be considered before applying compost to soil?
 Why is salinity an issue for high tunnel production?
 What happens when soil salinity is too high in high tunnel soils?
 What can be done to reduce salt levels in soils?
Students will apply what they learned about calculating fertilizer needs as
they complete the problems together in class. They will also apply this
through the lesson evaluation.
Students will complete the H.O. – “Inorganic Fertilizer Application
Worksheet” for the lesson evaluation. The principles involved in responding
to this question were utilized in the practice problems earlier in the lesson.