Family Farm Series Publications:
Vegetable Production
Plastic Tunnels For Early Vegetable Production
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This Plastic Tunnel publication is the result of many hours of work by
the author and Bill Fischer, who wrote the herbicide section of this booklet.
Richard Coviello, our entomologist, was also involved. His observations
demonstrated that tunnels can be very effective in keeping insects off
the plants. Roberta Cook, an economist from U.C. Davis specializing in
marketing, revised the marketing section of this booklet. Karen Klonsky,
a farm management specialist also from U.C. Davis revised the last section
dealing with how one goes about deciding whether plastic tunnels would
be a wise addition in one's farming operation. Bob Brewer, a specialist
headquarted at Kearny Agricultural Center in Parlier, helped us with the
necessary temperature measurements. Manual Jimenez, Farm Advisor from
Tulare County, conducted three years of trials with tunnels, mulches and
tomatoes.
Also, this publication would not have been possible were it not for the
editorial help provided by farm advisors, Aaron Nelson and Shannon Mueller.
To them and to my many staff assistants who helped me with the field trials,
harvests, analysis of the data, etc., a heartfelt thanks.
The first plastic tunnels were used in Fresno County by Richard Espinoza
to grow Japanese eggplants and long Chinese beans. Richard was introduced
to the use of plastic tunnels while on a tour of the San Diego Vegetable
Growers organized in 1981. Richard also build the first tunnel laying
machine and established tunnels in the subsequent years for many local
vegetable growers.
Many farmers helped us during all these years, when different tunnels,
crops and herbicides were evaluated. our thanks go to Daryl Bradburn from
Madera County, Curt Hirasuna, a former farmer from Fresno's immediate
west wide, The American Indian Council of Fresno, Frank and Kenny Lucero,
Joe Santellano and Nag Vang.
The field trials were supported in part by Swanson Irrigation, Dow Chemical-Agricultural
Plastic Division, T-Tape, Visqueen Plastics, Hardy and Chapin Irrigation,
and Germain Seed companies. Without their generous contributions this
work would not have been possible.
Lastly, but not least, my thanks to secretaries Rosaura Maldonado and
Wanda Palmer, who very patently prepared this publication for printing.
Pedro Ilic
Farm Advisor
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Many warm season vegetable crops can bring a higher price early in the
growing season before large supplies are available. In order to encourage
early vegetable production and capture the profitable early market, growers
can use plastic tunnels or hot caps. Recently, a few farmers have begun
using plastic mulches in combination with tunnels to speed up the harvest
date for some crops. However, plastic mulches by themselves, whether black
or clear, provide little extra heat to advance the harvest date significantly.
Many growers, who have used hot caps for years, are now using plastic
tunnels, because they provide more protection from frost, greatly speed
up the growth of the plants and are generally less expensive to install
and manage than hot caps.
What Are Plastic Tunnels?
Plastic tunnels are small greenhouse-like structures, covering the plants
along the row. These tunnels are 18" high by roughly 30" wide
at the base and are erected with wire hoops and covered with clear plastic.
The tunnels promote early growth by warming the air surrounding the plants,
using heat from the sun. The tunnels also protect plants from frost that
can destroy or damage them. Greater overall crop yields are obtained when
the plants come into earlier production and continue to bear throughout
the season. This combination of earliness and greater yields can significantly
increase profits for the growers (Figure 1).
Which Crops Should I Plant Under Tunnels?
The selection of the kinds of crops to grow under tunnels is an important
decision and should be made carefully. The choice should include the consideration
of the crops best suited for tunnel cultivation, projected prices over
the market period for the anticipated market, and expected yield on a
per acre basis.
Field trials and experience have shown that many crops can be successfully
cultivated under tunnels. They include: zucchini squash, chili peppers,
cucumbers, cherry and fresh market tomatoes, melons, green beans, Chinese
long beans, singua, moqua, and bitter melons. Bell peppers and eggplants
are difficult to grow under tunnels and should be grown by experienced
farmers only. Through experimentation, growers may find other crops that
may be grown successfully on their farm under tunnels.
What About Market Prices?
Although it's difficult, if not impossible, to accurately predict future
market prices, historical prices give growers an idea of how to time their
production. Figure 2 shows the average weekly price variation for Italian
zucchini squash at the Los Angeles terminal (wholesale) market, for the
March through October period. These prices represent the average weekly
lows and highs from 1984-1988, and are reduced by 15 percent to account
for wholesaler commissions. Hence, they approximate prices paid to growers,
as opposed to prices received by wholesalers.
If using tunnels, it permits shipping during early March, then clearly
growers could tap a market window. Farmers can compare these price data
with their projected production costs to assess the profitability and
risk associated with growing Italian zucchini squash under tunnels. If
prices have consistently been above the growers' expected production costs
for the intended shipping season, this serves as an indicator of potential
profit.
Using historical information is only one tool, and it is important to
note that market conditions can change dramatically from season to season.
consequently, before planting, growers should investigate the expected
market conditions for the upcoming season with handlers. Are there new
producing regions, or have existing producers expanded acreage? How about
international competition? Is it expanding, or contracting? Identifying
and maintaining a good relationship with reputable handlers and utilizing
publicity and available market information are vital parts of making sound
production and marketing decisions.
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There are several types of plastic tunnels growers can use. The type
used will depend on factors such as the crop to be grown and the capital
needed for the necessary equipment to erect tunnels in the field. Tunnels
which use two 3-foot wide plastic sheets stapled together at the top are
commonly used by farmers growing trellised crops such as cherry tomatoes,
long Chinese beans, and bitter melons (Figure 3). These tunnels are relatively
more expensive to put up, but require little equipment investment. Most
of the necessary operations tout them up are done by hand. However, the
bed and laying the plastic can be done with a machine.
The Spanish Tunnel: A Good Option?
Growers who plan to grow chili peppers, bush tomatoes, eggplants, green
beans, strawberries and other similar crops can use the Spanish tunnel.
This tunnel uses a high bed (7" to 10") and a single 6' wide
plastic sheet, 1.5 mil thick. The plastic sheet is usually perforated
for ventilation and temperature control.
The advantage of this tunnel is its ease of operation and management,
especially at venting and harvesting time. It require hoops of 7-gauge
galvanized wire, each approximately 90" long (Figure 4a). The hoops
have a small loop, the size of a quarter, approximately 10" up from
each end. The plastic on top of the tunnel is kept in place by twine,
stretched from loop to loop, running either from loop to loop on the same
hoop or diagonally, on the hoops giving the tunnel its half moon shape
(Figure 4b). The plastic on top of the hoops, forming the tunnel, rests
on the shoulder of the bed. The plastic is laid with the same equipment
used to lay the tunnels for trellised crops.
Although, farmers in Spain who use these tunnels to grow strawberries
do nut bury either side of the plastic, in Fresno County it is advisable
to bury at least one side. You should consider burying the side of the
plastic that faces the strongest, most sustained winds during the season.
When all danger of wind damage is past, the side buried under the soil
can be picked up. The plastic needs to be buried at the end of the tunnel
to insure it's tension during the season.
One disadvantage of using this tunnel is that extra hours of labor may
be required to untangle the hoops from each other. These hoops, because
of the small loops at their ends, tend to tangle more readily and any
other wire hoops.
Is There Equipment To Lay Plastic Tunnels?
To lower costs of production, growers have begun to use specialized equipment
to put the hoops in and lay the plastic over the hoops in one single operation.
There are a number of machines on the market. All of them work well, provided
that the soil is leveled and in good tilth (Figure 5).
How Do You Build Plastic Tunnels?
1. Prepare the soil as you usually would for planting vegetable crops.
Pay particular attention to leveling the soil, since unleveled soil will
be the biggest source of equipment failure and wasted time.
2. For some weed control methods you should act now to prevent weeds from
becoming a problem inside your tunnels. For an expanded discussion of
weed control using plastic mulches, strip fumigation, broadcast fumigation,
herbicides, and solarization, see herbicide discussion on page 5.
3. Whether or not you plan to use drop to irrigate and fertilize your
crop, incorporate approximately one-third of all the nitrogen and all
the phosphorous and potassium your crop will need during the season for
maximum production. Follow general fertilization requirements for each
crop.
4. For some systems, make the bed and lay plastic and drop in one single
operation. (If a tunnel-making machine will be used, plant transplants
at this time, since this machine will install the hoops and plastic in
one single operation).
5. Install hoops ever 7 ft. (closer of necessary in windy areas).
6. Plant transplants or seeds, if not done in step 4.
7. Close tunnels.
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Plastic tunnels increase maximum daytime temperature significantly, but
only increase minimum night temperature by a few degrees. A clear cool
day with a maximum temperature of 60°F can produce inner temperatures
well into the 100's in an unvented tunnel. By comparison, when outside
temperatures are near freezing at night, temperatures may only be one
to three degrees warmer inside the tunnel. It is even possible, under
certain weather conditions to experience cooler temperatures inside the
tunnels.
Consequently, there is a limit to how early in the season growers should
set transplants within tunnels. Some crops, such as tomatoes, can be planted
the first of February in Fresno County. Others, such as chili peppers
and zucchini, do better when planted in the middle of February. Eggplants
do better when planted in late February. The point to remember is not
to plant too early since it may be costly if the weather becomes abnormally
cold or wet.
For a given crop, transplanting when compared with direct-seeding generally
accelerates the harvesting date. However, in one observation trial, cherry
tomatoes grown from seeds were as early and as productive as when they
were grown from transplants.
Do Plastic Mulches Make Sense?
Black plastic mulch is the most often-used plastic under tunnels. Its
thickness varies from 1 to 1- 1/2 mils. Growers like to use it to control
weeds. In field trials, black mulch has not effectively controlled nutsedge,
although, it has been very effective with all other weeds. Reports and
field trials comparing the use of clear to black mulches under tunnels
indicate no significant difference in yields. This held true for many
different vegetable crops grown in this manner (Figure 6a).
Recently, a brown plastic mulch has been introduced in the market. This
plastic combines the positive aspects of both the clear and the black
mulches. In trials in Israel and California, it has controlled weeds better
than clear mulch. It is also warmer than the black mulch, but not as warm
as the clear mulch.
In the last few years, several companies have begun to offer photodegradable
mulches. These mulches break down with the action of sunlight. They are
formulated to break down after a set number of hours of exposure to sunlight.
When the breakdown process starts, the degradation continues even in the
absence of sunlight. If you plan to use photodegradable mulches, you must
keep in mind the geographic area where they will be used, and the crop
to be mulched. The growth habit of the crop and the number of days from
planting or transplanting to harvesting, are very important in determining
the appropriate plastic mulch formulation.
How Do You Plant?
Many growers plant transplants by hand, especially if they use black
or clear mulch on beds. However, this is too costly for large acreage.
Recently, a few growers have begun to use specially-designated transplanters
to set to plants in e field. These transplanters perforate the plastic
mulch and set the transplants in the bed in a single operation (Figure
7).
Is Venting Needed?
For most crops, there is little need to vent during the first month of
growth, but the need for venting increases as the season progresses. Cucurbits
such as squash and watermelons need little venting prior to pollination.
Peppers, tomatoes, and green beans are more sensitive to high tunnel temperatures.
If inner temperatures reach the high 90's, damage can occur to the growing
tips of tomato plants. Beans and peppers can be set back significantly.
Usually heat stress symptoms on these plants include a gradual yellowing
of the leaves.
What About Frost Protection?
When frost is anticipated, ground water should be run on the bed inside
the tunnels. This can be easily done if a furrow has been included for
irrigation and frost protection inside the tunnels. Check your water to
determine its temperature. Water at 60°F can go a long way to protect
your plants on a frosty night. Care should be taken not to drown the plants,
since too much water will rot the roots (Figure 8).
If drip irrigation is used and the bed is somewhat dry, the water should
be turned on early to capture as much heat as possible. However, frost
protection afforded by drop is minimal. If the soil is sandy and without
water penetration problems, water may be run between the tunnels. This
will warm the soil considerably and can help save the crop.
Which Irrigation System Is Best?
Whichever system is used to irrigate the crop inside the tunnel, it must
meet the water needs of the plants at all times. Furrow irrigation is
the most widely-used system of irrigation (Figure 8). It is important
to have the irrigation furrow inside the tunnel close to the transplants,
where water and nutrients can reach them easily. Experience with tunnels
over the years has shown that irrigating with furrows outside of the tunnel,
especially in sandy soils, where water does not effectively sub up, is
not advisable since the water does not reach the transplants effectively.
The results are plants are severely stunted for lack of water. Drip irrigation
is becoming more attractive to farmers as they learn to use it more effectively.
However, it has a number of disadvantages when compared with furrow irrigation.
It is more costly to set up and it can plug up. It also requires greater
knowledge of the water needs of the crops. Furthermore, drip must be maintained
over time for maximum efficiency. For those who have experience and know
how to use it, drip can be an effective tool in minimizing irrigation
costs, water use, and fertilizing expenses. When using drip, care should
be taken in laying the drip line or tape, following the manufacturer's
suggestions. If this is not done, poor irrigation uniformity may result.
What Fertilizers Do I Use?
Vegetables grown under plastic tunnels must be fertilized with precision
to avoid nutrient deficiencies during the growing season. Even though
you may plan to apply liquid fertilizers through the drip, it is advisable
to consider all the options available to maximize soil fertility prior
to planting the crop. Manures and cover crops should be considered whenever
possible. Manures in sandy soils are particularly attractive since they
add a host of nutrients and micronutrients to the soil. However, if manure
is used, care should be taken to insure that it is free of viable wee
seeds and to leach the salts from the root zone. If this is not properly
done, the crop may be affected by the high salt content of manures, especially
from poultry.
Whether you use drip or another irrigation method, highest crop yields
are obtained when one third of the nitrogen and all the phosphorus and
potassium the crop will need during the season are incorporated at planting
time. Additional nitrogen should be applied as needed, as the crop develops
and matures.
There are complete fertilizers especially formulated for drip irrigation.
It is best to follow the prior recommendation before planting. Applying
complete fertilizers through the drip system is often expensive and can
clog the emitters.
Are Pest And Diseases a Problem?
During the ten years that growers have used plastic tunnels in Fresno
County, no serious outbreaks of pests and diseases have been reported.
Trials in the field with plastic tunnels and different crops have shown
that tunnels do protect the crop from insects well into the season. However,
plants should be insect-free at transplanting, since the warmer environment
will stimulate insect development, usually aphids, and damage the plants
(Figure 9).
Is Wind A Problem?
Many of the difficulties growers have experience using plastic tunnel
technology have resulted from inadequate planning in dealing with wind
conditions.
Growers must be aware of the wind conditions in their area before deciding
to use tunnels. Plastic tunnels are not designed to withstand high winds
or whirlwinds (Figure 11). Many of the wind problems can be attributed
to:
1. Too great a distance between hoops.
2. Hoops too thin and short.
3. Plastic sheet not sufficiently strong or badly placed over the hoops
forming the tunnels.
Placing the hoops closer together can effectively minimize wind problems
under most circumstances.
Other Problems.
Farmers who may want to use tunnels in heavy soils may experience flooding
in wet, rainy years. Heavy soils, which do not drain rapidly, can easily
rot the roots of the plants. For this reason, it is best to avoid them
for tunnel frown vegetable crops. If heavy soils have to be used, especially
in areas where one to one and a half inches or rain can fall in less than
24 hrs., adequate provisions have to be made to drain the water out of
the tunnels as fast as possible. In San Diego County where heavy rains
during the growing season can be a problem, growers use extra deep furrows
between the tunnels to move the rain water out of the field.
Heavy soils are also difficult to work, slow in warming up in the springtime
and cloudy, which makes the necessary cultural operations such as plastic
laying and cultivation difficult to perform.
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Weed control is an essential part of crop production. Without effective
weed control, crops cannot be produced profitably. Annual and perennial
weeds compete effectively for nutrients and water with all crops. In many
cases weeds can become hosts to certain viruses and insects that can attack
the crop. The presence of weeds can make the harvesting operation more
difficult and expensive.
The environmental conditions under plastic tunnels favor the rapid growth
of weeds. Unless they are controlled effectively, weeds can adversely
affect the growth of the crop and delay fruit set, nullifying the advantage
of using plastic tunnels.
How Important Is Planning Ahead?
Weed control, to be effective, requires advance planning and timeliness
of performance. "Prevention is the best cure" is an adage that
should be heeded by vegetable growers. The cost of weed control under
plastic tunnels can be greatly minimized by proper site selection. Growers
should avoid establishing tunnels in fields heavily infested with annual
or perennial weeks or fields surrounded by heavy weed infestations. Through
advanced planning, weed-control costs can be significantly reduced by:
pre-irrigation, repeated shallow cultivations, solarization, fumigation,
and with the use of selective herbicides.
Does Weed Control Begin Before Planting?
Yes! Follow these methods:
Pre-irrigation. The area where the tunnels will be constructed can be
irrigated and the germinated weeds destroyed with shallow cultivation.
Deep cultivation brings up weed seeds from a greater depth. If time allows,
an area can be irrigated two or three times to germinate weed seeds.
Solarization. Covering moist soil with clear plastic has been demonstrated
to be effective in killing not only weed seeds but insect and disease
organisms as well. The soil must be wetted or irrigated before the plastic
is installed. The soil must remain covered for six to eight weeks when
the air temperature is above 80°F. Water can be applied under the
plastic cover through low volume emitter drip lines. To obtain good control,
the plastic must be in close contact with the soil: air pockets will reduce
its effectiveness (Figure 11).
Fumigation. Fumigating the soil with methyl bromide is the most effective
method of controlling weeds and other harmful insects and disease organisms.
It kills seeds, roots, rhizomes, bulbs and tubers of plants as well as
nematodes. Methyl bromide, sold under several trade names, is very poisonous
to humans. It has to be applied under an airtight (plastic) cover. Commercial
applicators are available, and it is best to hire them for treating large
areas (broadcast) or for strop (bed) fumigation (Figure 12). A permit
for the use of methyl bromide must be obtained from the Agricultural Commissioner's
office.
To obtain the best results, the area to be fumigated should be irrigated
and prepared for planting. The soil temperature should be above 60°F
at a four to five inch depth. The airtight cover should not be disturbed
for three days. Following removal of the cover, the soil should be allowed
to aerate two or three days before planting seeds, or five or six days
before planting seedlings.
What Herbicides Do I Use?
Herbicides should be used only if they are labeled for the specific crop.
Herbicides are available on the market than can be applied before the
crops are planted (preplant). Some can be applied after the crop seeds
are planted, but prior to their germination or emergence (preemergence).
Still others can be applied after the crop is growing or after transplanting
(postemergence).
Prior to Planting. Following land preparation and before planting, emerged
weeds can be destroyed with the use of Gramoxoneâ or Roundupâ.
When weeds are young they are easy to kill and less herbicide is needed.
Gramoxoneâ is a contact herbicide and will kill only the parts of
the plants that are actually sprayed. Thorough coverage is therefore essential.
Roundupâ is a systemic herbicide that moves from the treated to
the untreated areas within the plant. soon after the application of these
herbicides, seeds or transplants can be planted into the treated areas.
(Note: the use of Gramoxoneâ requires a permit from the Agricultural
Commissioner and protective equipment must be worn during its application.)
Soil persistent herbicides. There are several herbicides marketed for
use in vegetable crops that can be applied and incorporated into the top
2 to 2-1/2 inches of soil and will provide long lasting control of weeds
without causing injury to the crop. However, very little experimental
work has been done in evaluating the sage and effective use of herbicides
under plastic tunnels. The following herbicides were evaluated in limited
trials in Fresno County. It must be emphasized however, that these herbicides
are not labeled for use under plastic tunnels (Figure 13).
Devrinolâ (napropamide) is registered for use in tomatoes, peppers,
and eggplant. Its sage and effective use has been demonstrated in many
trials. It is used extensively in commercial fields under conventional
cultural practices. Under plastic tunnels it provided effective control
of grasses and many broadleaf weeds. It was applied prior to the establishment
of the tunnels and incorporated to a depth of 2-1/2 inches. Devrinolâ
under plastic mulch or plastic tunnels where trip irrigation was used
provided short lived control.
Treflanâ (trifluralin), preplant incorporated, looks very promising
on transplanted tomatoes and peppers. Under plastic tunnels it exhibited
good crop selectively. Treflanâ does not control weeds in the mustard,
nightshade and thistle families, commonly found infesting crops planted
in late winder or early spring.
Prefarâ (bensulide) looks very promising and safe to use in tunnels
for the control of annual grasses and a few broadleaf weeds. Tomatoes,
peppers, eggplant, squash and cucumber showed good tolerance to Prefarâ.
Alanapâ (naptalam) looks very promising for use on transplanted
and direct seeded squash and cucumbers. It is effective on a large number
of broadleaf weeds but less effective on grasses. Alanapâ has relatively
short residual activity. The combination of Alanapâ plus Prefarâ
were also included in the trials under plastic tunnels to obtain a broader
spectrum of control.
None of these herbicides evaluated under plastic tunnels controlled all
of the annual grasses and broadleaf weeds. Therefor, combinations of herbicides
and sequential applications may often have to be used. Additional studies
are needed.
Weed control after planting. Following transplanting or after crop emergence,
hand pulling, hoeing, shallow cultivations, or herbicides can be used
to control weeds. Regardless of the method, they should be used while
the weeds are seedlings ¾ before they compete with the crop. They
are easier to control in their seedling stage.
Hoeing. The available mechanical cultivators cannot be used safely around
tunnels because severe damage to the tunnels would occur. Hand hoeing,
therefore, is the most practical method of controlling weeds under plastic
tunnels. Hula hoes are especially well adapted for shallow cultivation
as they have no sharp points and can be safely used in tunnels and adjacent
to the crop plants. Hula hoes can be used most effectively on weed seedlings
before their extensive root system develops.
Herbicides. Several herbicides have been registered recently for the
selective control of most annual and perennial grasses in vegetable crops.
Fusilade 2000â is labeled for use in onions and garlic. Poastâ
is registered for use in numerous vegetable crops including tomatoes,
eggplants, cucumbers, melons, summer and winter squash.
Poastâ was demonstrated to provide very effective control of grasses
except annual bluegrass without adversely effecting the broad-leaved vegetable
crops. The herbicide, in combination with a paraffin based adjuvant, needs
to be applied while the grasses are young and growing vigorously. Grasses
will not be controlled adequately when they are stressed for moisture
or are beyond their early stages of growth. Consult the label for the
rate of application and whether they can be used under your cultural conditions.
Gramaxoneâ and Roundupâ can be used effectively to control
emerged weeds near the field, but not within the tunnels, since these
herbicides are not registered for use after vegetable crops are planted
in the field. The crop plants should not be contacted and drift of small
particles onto the crop must be prevented while spraying. This is especially
important when Roundupâ is used. This can be accomplished by using
a hood that can be easily constructed (Figure 15). An empty one-galling
plastic container or a 3-pound coffee can may be used to construct an
effective and inexpensive hood. Also, the top of a plastic bottle can
be cut off and a hole made in the bottom through which the spraying nozzle
is inserted. The herbicide is sprayed under the hood.
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You can use a number of methods to help you decide whether plastic tunnels
would be a wise addition to your farming operation.
Here is a simple method called partial budgeting that you can use to
help you decide on any changes you may want to make in your farming business.
It requires you to carefully assess changes in income and expenses that
would result from switching from your current practice to one that may
be adopted in its place. It is called a partial budget because it is not
necessary to calculate the expenses that would be the same for either
practice.
Of course, before you can begin the analysis, it is desirable to know
exactly what new practice you are considering. Decide what crop you want
to grow using tunnels and what kind of tunnels you want to use and have
some idea of changes in production costs associated with tunnels including
water and pest control. The other sections of this publication should
be helpful in doing the partial budget analysis.
After carefully evaluating the plastic tunnel system, you must compare
the pros and cons of using it. It all comes down to the bottom line. Do
you make or lose money by using tunnels?> To answer this question estimate
the increase in income by switching to plastic tunnels, and any reduction
in costs by abandoning the system to be replaced by tunnels and income
given up by switching to the plastic tunnel system. Finally, by adding
up the increases and decreases in income and expenses you can determine
the bottom line.
Let's look at the decision to use plastic tunnels for a vegetable crop
that you may be already growing. For example, you may be deciding whether
or not to follow your current practice of growing zucchini squash without
tunnels or switch to growing zucchini squash under plastic tunnels. The
following questions must be answered.
What will be the added income derived from plastic tunnels?
The added income is the gross income that you expect from your crop grown
under plastic tunnels. Gross income is simply price per box multiplied
by the number of boxes. Therefore, income changes as a result of a change
in the price received per box, a change in the number of boxes produced
or both. Well managed plastic tunnels generally translate into greater
yields per acre and better prices per box in early markets.
In zucchini squash the increase in production levels has ranged from
30 to 100 percent. A realistic projection of the price received is critical
to your decision regarding switching to tunnels.
What will the added expenses be if you use tunnels?
If you are deciding whether or not to use tunnels on a crop you are already
growing, then you can ignore any costs that would be the same in the old
system and the new system such as bed preparation. The only expenses you
need to consider in this case are the costs associated with the use of
tunnels.
Included in the costs is the plastic, rent or purchase of specialized
equipment, and labor to erect the tunnels. Additional labor is also needed
to manage the tunnels throughout the growing season. Allow for extra hours
of labor due to inexperience the first year. Also include the cost of
frost control if you think that might be necessary.
Will there be any reduced expenses associated with this change?
In planning to use tunnels are you giving up another cultural practice?
If so, what are the expenses eliminated? Perhaps you are evaluating using
tunnels instead of hot caps. In this case, all of the expenses associated
with using hot caps will be eliminated. These savings need to be computed
and included in the analysis.
What will be the decreased income because of the change to plastic tunnels?
The reduction in income is simple the expected gross income from the
crop grown without tunnels, as compared to the income you would have had
if you grew the crop with tunnels.
The final step in the analysis is to add up all the increases and decreases
associated with switching to using tunnels. The total change in profits
is the difference between the change in income and the change in expenses
as follows:
ADDED AND REDUCED INCOME = NET CHANGE IN INCOME
ADDED AND REDUCED EXPENSES = NET CHANGE IN EXPENSES.
The change in net profit can then be calculated as follows:
NET CHANGE IN INCOME + NET CHANGE IN EXPENSES = NET CHANGE IN PROFIT.
If the net change in profit as a result of the switch to tunnels is positive,
then tunnels may be for you. If the net change in profit is negative,
that is, the analysis predicts that your profit will be reduced by switching
to tunnels, then tunnels probably aren't for you.
Other things that you may want to consider in this analysis are:
1. Your available capital situation for the initial investment to purchase
the materials.
2. Equipment needed to lay plastic tunnels in the field.
3. Your management time, given the other crops you may have in the field
at the time.
4. Your labor situation, since tunnels can be labor intensive at certain
times of the season.
5. Water resources¾do you have a source of ground water that may
be needed for frost protection early in the season?
Some farmers are simply not geared for tunnel farming at all. They do
not have the appropriate equipment, poor soils, little or no capital and
almost no experience with early marketing of vegetables. For these farmers,
plastic tunnels may mean losses they cannot afford.
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Cost Analysis Work Sheet - 1989
Prepared by Pedro Ilic, Fresno County Farm Advisor
Sample costs to produce Jalapeño Chili Peppers in Fresno County
are based on 800, 10 lbs. boxes per acre. Field labor is about $4.50 per
hour cost to the grower. A 70 hp diesel powered tractor per hour cash
costs $6.00. Grower has invested in various specialized pieces of equipment
to lay mulch, build tunnels and fumigate. Peppers are planted on a single
row 12" apart, 6' of distance between beds. This is considered to
be a crop on a 80-acre farm, where raisin grapes and vegetables are produced.
| Sample Costs | | My Costs | |
| Per | Per | Per | Per |
| Acre | Box | Acre | Box |
| PRE-HARVEST COSTS: | | | | |
| Land Preparation: | | | | |
| Plow: 3 hrs. tractor & labor | $31.50 | | | |
| Disc: 1 hr. tractor & labor | $10.50 | | | |
| Springtooth: 1 hr. tractor/labor | $10.50 | | | |
| Laser Leveling: | $75.00 | | | |
| Bed Fumigation (CH3Br): | | | | |
| 2 hr. labor/tractor | $21.00 | | | |
| CH3Br-240lbs. at 1.05/lb. = 80 lbs. | $84.00 | | | |
| Plastic Mulch/Tarp: | $171.00 | | | |
| Drip Tape: | $145.00 | | | |
| Planting: 7000 plants at $35/1000 | $245.00 | | | |
| labor 10 hrs./ 2 hrs. tractor | $57.00 | | | |
| Tunnel Plastic: | $248.00 | | | |
| Construction: | | | | |
| 12 hrs. labor / 3 hrs. tractor/machine | $72.00 | | | |
| Fertilization: | | | | |
| preplant 300 lbs. -15-15-15 | $42.00 | | | |
| labor/tractor .5 hrs | $5.25 | | | |
| Sidedress: | | | | |
| 300 lbs. 15-15-15 | $42.00 | | | |
| labor/tractor .5 hrs. | $5.25 | | | |
| Liquid Fertilizer | $75.50 | | | |
| Irrigation: PG&E - $50 @ 3 months | $150.00 | | | |
| Venting: 30 hrs. labor | $135.00 | | | |
| Tunnel Removal: | | | | |
| 27 hrs. labor & 2 hrs. tractor | $133.50 | | | |
| Staking & Tying: 36 hrs. | $162.00 | | | |
| material cost | $20.00 | | | |
| Cultivating: 16 hrs. labor | $72.00 | | | |
| Tractor Cultivating: 4 hrs. labor 1.5 tractor | $26.00 | | | |
| Miscellaneous Expenses: 6% | $128.00 | | | |
| Office Expenses | $118.20 | | | |
| TOTAL PRE-HARVEST COSTS | $2,266.80 | $2.83 | | |
| Jalapeño Chili Peppers | | | | |
| Sample Costs | | My Costs | |
| Per | Per | Per | Per |
| Acre | Box | Acre | Box |
| HARVEST COST | | | | |
| Picking: | $1,000 | $1.25 | | |
| Box: | $344 | $0.43 | | |
| Packing: | $200 | $0.25 | | |
| Transportation: | $160 | $0.20 | | |
| Cold Storage: | $80 | $0.10 | | |
| TOTAL HARVEST COSTS | $1784 | $2.23 | | |
| TOTAL CASH COSTS | $4050.80 | $5.06 | | |
| Depreciation: | | | | |
| Tractor 75 hp (large) | $43.00 | | | |
| Kubota tractor | $50.00 | | | |
| Tunnel machine | $35.00 | | | |
| Equipment - wire hoops | $41.00 | | | |
| Shed (other) | $3.00 | | | |
| Drip Irrigation | $70.00 | | | |
| TOTAL DEPRECIATION | $242.00 | 30¢ | | |
| INTEREST ON INVESTMENT AT 8% | | | | |
| 1/2 cost of $30,000 for 80 acres | $15.00 | | | |
| Tractor, tunnel equip. & other wire | $54.00 | | | |
| Shed | $2.00 | | | |
| Drip Irrigation: (filters, mains, etc) | $28.00 | | | |
| TOTAL INTEREST ON INVESTMENT | $99.00 | 12¢ | | |
| TOTAL COST OF PRODUCTION | $4391.80 | $5.48 | | |
| COST OF VARYING YIELDS: |
|
|
|
|
|
| 10 Lbs. Boxes |
|
|
|
|
|
| COST |
400 |
600 |
800 |
1000 |
1200 |
| CASH COST |
$10.12 |
$6.75 |
$5.06 |
$4.05 |
$3.37 |
| TOTAL COSTS |
$10.97 |
$7.31 |
$5.48 |
$4.39 |
$3.65 |
CAUTION WARNING ON THE USE OF CHEMICALS CAUTION
Pesticides are poisonous. Always read and carefully follow all precautions
and safety recommendations given on the container label. Store all chemicals
in their original labeled containers in a locked cabinet or shed, away
from foods or feeds, and out of the reach of children, unauthorized persons,
pets, and livestock.
Recommendations are based on the best information currently available,
and treatments based on them should not leave residues exceeding the tolerance
established for any particular chemical. Confine chemicals to the area
being treated. THE GROWER IS LEGALLY RESPONSIBLE for residues on the grower's
crops as well as for problems caused by drift from the grower's property
to other properties or crops.
Consult your county agricultural commissioner for correct methods of
disposing of leftover spray materials and empty containers. Never burn
pesticide containers.
PHYTOTOXICITY: Certain chemicals may cause plant injury if used at the
wrong stage of plant development or when temperatures are too high. Injury
may also result from excessive amounts or the wrong formulation or from
mixing incompatible materials. Inert ingredients, such as wetters, spreaders,
emulsifiers, diluents, and solvents, can cause plant injury. Since formulations
are often changed by manufacturers, it is possible that plant injury may
occur, even though no injury was noted in previous seasons.
To simplify information, trade names of products have been used. No endorsement
of named products is intended, nor is criticism implied of similar products
that are not mentioned.
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Crop Production
