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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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Labor Intensive Vegetable Crops/Small Farm Fresno County

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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Types of Tunnels

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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What About Farming and Cultural Practices With Tunnels?

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

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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Are Tunnels For You? 
Here is an Easy Way to Decide

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:


The change in net profit can then be calculated as follows:


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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Jalapeño Chili Pepper Production For Fresh Market

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 CostsMy Costs
  Per AcrePer BoxPer AcrePer Box
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      
12 hrs. labor / 3 hrs. tractor/machine $72.00      
preplant 300 lbs. -15-15-15 $42.00      
labor/tractor .5 hrs $5.25