• Why Not Try Tunnel Farming?

    By “Awake!” correspondent in South Africa

    “WRAP yourself up warmly,” our guide suggested. “The outside temperature is six degrees Celsius below freezing [21 degrees F], but fortunately there is not much wind at this time of the year.” We stepped outside, leaving behind a warm, luxuriant natural hothouse atmosphere, where tons of ripening tomatoes hung on their vines, ready for the pickers.

    The dramatic change in temperature, along with the high altitude of 1,800 m (6,000 ft.), caused us to gasp and to clutch our coats more tightly about ourselves as our guide closed the large gates behind us.

    We had just seen the evidence of man’s ingenuity in working closely with “nature” to produce vegetables, including delicious tomatoes, in huge aboveground plastic tunnels. This was done in the depths of winter by special soilless culture methods. Incidentally, each tunnel is about 51 m (167 ft.) long by 3 m (10 ft.) high and 7.5 m (25 ft.) wide.

    Back in the farm office, our guide told us:

    “So popular has this method become in the Republic of South Africa that it is not unusual to ride along country highways, and even city streets, and see the bright glint of these plastic tunnels in gardens and small agricultural holdings.

    “Not only is this popular as a hobby for many housewives and busy executives who need relaxation at the end of the day, but it is also most profitable, giving net returns, after capital depreciation, of between 60 and 70 percent.”*

    As we listened, our guide explained that in past decades many thousands of householders in the northern hemisphere erected and enjoyed working in glass hothouses, raising flowers, ferns, potted plants and a few vegetables. In the sunny southern hemisphere there seemed to be little need for such hothouses because there was plenty of sunshine and virgin soil. Also, with relatively little attention, the ground produced all that the people needed.

    “But,” our guide said, “with current rocketing land prices, high labor rates, increasing costs of electricity and fuels, plus the worldwide population explosion, the situation has undergone a drastic change.”

    From Hydroponics to Soilless Culture

    The theory and practice of hydroponics (cultivation of plants in water) has been known for a long time. It had been developed considerably but suffered many setbacks. For instance, the need for brick-lined canals and the high costs of delivered river stone, crushed rock and sand materials used for filtration purposes made hydroponics too expensive as a hobby for the average wage earner.

    At this point, we asked: “What caused the swing to this extension of the farming method?”

    Our guide replied: “Probably the more important reasons are the increasing demand for good-quality fruit, linked with a worldwide swing in eating habits to higher fresh-salad intake per capita. Additionally, because the returns are so good, it is possible for the average wage earner to invest in this new concept.”

    The guide then showed us the thousands of healthy tomatoes already neatly packed in cartons and ready for delivery to the stores of the Witwatersrand. Certainly the size and shape were uniform. A housewife would not have to finger each tomato to select what she needed. The healthy, consistent shape and appearance meant she was assured of the best results on the table.

    We asked our guide: “Can one grow only tomatoes in the plastic tunnels? And, how is it possible to achieve such results without using soil at all and when outdoor temperatures are below freezing?”

    He remarked: “Not only tomatoes, but really any vine crop, can be successfully cultivated in the plastic tunnels. In these, we also grow cucumbers, green peppers, beans, strawberries and sweet melons, as well as white and yellow maize. Some of these crops, however, are not profitable because of the high foliage volume. Probably the most profitable crops to date have been tomatoes, followed by strawberries, green peppers and cucumbers.”

    “Answering the second part of your question,” he continued, “we have found that during winter daytime we can actually leave the tunnel gates open, provided that we place over the entrance a special wind net with about 40 to 50 percent shade value. This tends to control both the inward flow of cold air and the loss of trapped sun and plant heat. The midday tunnel temperatures are in the region of 25 degrees C [77 degrees F]. So, if we close the gates about 4 p.m., the ‘sealed-in’ warmth will carry the plants through the cold night without loss of plant growth.”

    “Of course,” he added, “in colder climates, higher altitudes and lower sunshine value zones, internal heating would be needed. We are experimenting with solar-heated water, piped underground and running the full length of each tunnel. Although the capital investment in solar panels is high, there is no other expense, no oil to pay for; nor is there any coal smoke and air pollution.”

    Plants Grown Above the Ground

    What we had seen in the giant tunnels certainly had been enlightening. Each tunnel contained 1,200 robust, thriving tomato plants, potted in vermiculite (exploded mica) and fed nutrient water from micro tubes set in a 50-mm (2-in.) main plastic supply pipe.

    Each plant was individually housed in a plastic pocket filled three quarters full with vermiculite. One micro tube per plant allows sufficient drip-fed nutrient water to nourish the roots for 24 hours. Beneath the plastic pockets, laid out on a perfectly level sand or earth floor, a black plastic sheet in wide strip form acts as a mulch, keeping weeds under control and insulating the containers from the cooler earth temperatures beneath. In this manner, root systems are also totally protected from the disease known as eel-worm.

    Outside each tunnel, a 1,893-L (500-gal.) galvanized water tank on a brick stand acts as a ‘header tank’ to the main flow and micro tubes. A single tankful, with powder nutrients mixed directly in the water, provides nearly two L (1/2 gal.) of water, carrying all the essential elements, to each plant daily. In order to prevent wastage, this is fed into the main plastic pipeline through a single gate valve.

    Each plastic pocket has holes punched at a one-L level. As soon as liquid begins to dribble from these holes, the gate valve is closed off. Watering is done twice a day, taking a total of only 10 minutes daily—certainly a great labor saver in itself.

    Minimum Labor Required

    The simplicity of the arrangement was stunning, but we had to know more. So we asked our patient guide, who also owned the farming unit: “How many people are needed to work in these tunnels?”

    “To answer that,” he replied, “we should consider what does not need to be done. For instance, we have no weeds to contend with because of our black plastic mulch. Another factor is that water pipes are permanently anchored in position. So we do not have to move irrigation equipment from point to point. We just turn the tap on.

    “On the other hand, what we have as daily routine is, first, a quick inspection of plants for leaf curl, rust or damage, followed by a nipping out of unwanted growth to permit good fruiting and ventilation. Thereafter, we pick ripe fruits and take them to the pack house.

    “The water and nutrient mix is then made in each outside tank, followed by the first watering for the day. Then the doors are opened and the nets dropped, if necessary. Oh, we may also need to ventilate the sides on really hot summer days. This is done merely by opening the roof at the plastic lap-overs, or, in the more sophisticated tunnel models, by rolling the bottom edges upward on mechanical roller shutters. So you can see how one person can easily care for two large tunnels without being overworked.”

    With respect to the profitability of tunnel farming, our guide was not in doubt. He pointed out that, while the capital investment was high, the relative cost of buying suitable farming land, fencing, implements and insecticides, as well as road-building expense, was far higher than tunnel cost per ton produced. In any case, most of the soil would have to be heavily fertilized and treated before planting.

    Tunnels can be erected on level ground of any type and texture. All one needs is a firm floor surface on which to place the plastic packets and the water piping.

    Because of the bow-shaped design of the tunnels, their tubular structure absorbs winds of up to 120 km/hr (75 mph) without damage to the tunnel or the plants. When a tunnel is erected with gates facing north and south, the sun’s rays are all absorbed into the structure from sunrise to sunset.

    Profitable as a Hobby—or a Business

    Since tunnel farming is possible near the big population centers, transport costs and losses from devaluation of fruit in transit are reduced.

    Apart from the consistent quality and low loss factors, through tunnel farming it is possible to give attention to methods of increasing fruit yield per plant, as well as mass yield per individual fruit. For instance, under normal growth conditions and with average attention, the yield per plant may vary between five and eight kg (11 and 18 lbs.) per plant. By judicious thinning and restriction to 10 fruits per truss, plus a limitation of 10 fruit trusses per plant, the yield can be increased to as high as 12 kg (26 lbs.)! Additionally, the fruit quality and flesh mass improve.

    Tunnel farming enables housewives, doctors, business executives and children to acquire a new outlook. There is pleasure and satisfaction in being close to plant life, which flourished so abundantly in the original paradise garden that God made for mankind. (Gen. 2:8) As one doctor remarked: “After a day spent attending to sick, diseased, maimed and depressed patients, I come back to my tunnel plants and see joy and sparkling life. Why, I can actually ‘see’ the Creator in the plants around me!”

    We had yet another question for our guide: “If we wanted to set up a tunnel and work it as a family, on what sort of expenditure should we plan?”

    “To answer that,” he said, “we should view matters from one specific type of crop—tomatoes, for instance. The gross earnings per kg may be expected to average 35c [40c, U.S.]. Working on the basis of two yearly crops of 1,200 plants each and six kg of fruit per plant, earnings would amount to a substantial sum.

    “On the other hand, the tunnel is an expensive unit, costing R3,000 [$3,400, U.S.] complete, including all piping, plastic, pockets, nutrient and vermiculite. Depreciation of 15 percent a year, plus plastic replacement cost, as well as the purchase of seed, pesticides, extra nutrients and vermiculite, in addition to water, packaging and transporting costs would raise the outlay considerably.

    “If you are going to work the tunnel as a family, you may or may not charge yourself for labor. But if you were to hire one part-time laborer, this could raise your costs to about R2,000 [$2,300, U.S.] a year. After your initial outlay, that leaves you a handsome profit, especially if you want to be independent of a ‘boss’ or your present job.”

    Our guide’s practical and reassuring answers to all our questions left us in no doubt that tunnel farming has come to stay. Financially, physically and, yes, mentally too, tunnel farming can be highly rewarding for anyone.


    This seems to be an exceptional case. One expert considers net returns of between 30 and 40 percent to be more likely.

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