Veggie Tunnel Basics

Why a Veggie Tunnel?

A Veggie Tunnel (VT) is a semi-hot-house into which certain vegetables may be planted for better growth and yield.

The advantages of VTs are:

1.      Protection against harsh sun that will damage plants during pro-longed exposure.

2.      Protection against strong winds that will damage plants if unprotected.

3.      Protection against strong rain and hail that will crush the plants if unprotected.

4.      Better water utilisation due to the hot-house effect which means less evaporation.

5.      Better protection against certain insects that will devour the plants or cause disease to the plants if exposed.

6.      Better yield per area if compared to open crop practice.

7.      Less subjected to seasonal crop planting due to the hot-house effect.

8.      Simple and cost-effective drip systems can be used to water the plants twice a day.

9.      The heavy gauge planting bags means that crops can be grows irrespective of the soil quality.

10.  The planting bags protects the plants against a lot of disease and pest from the surrounding soil.

11.  The plants are grown in a ‘sterilised medium’ and fed exactly what they need by means of fertilizer which means little or no disease, fungus and pest.   

Basic layout

The basic layout of a VT is in the form of an elongated igloo tent.

The standard tunnel is 12m by 3.8m and made of shade-net 6m wide. The netting is 6m wide as a standard.

Both front and rear is closed off and the front is fitted with 2 x 1.5m zips to ease entry into the tunnel.

The tunnel is supported by arches made of 32mm electrical conduit (pipe), every 2 meters apart. The conduit are cut into lengths of 2m for easy transport. This can be replaced with solid 6m pieces to eliminate the use of connecting sleeves.

The connecting sleeves are made of a class A high pressure plastic pipe with 33mm inside diameter, cut into lengths of 200mm. A steel nail is driven (hit) into the pipe, in the middle to prevent the sleeve from sliding sideways over the 32mm conduit.

The ground layout for the straight steel pegs of 12mm x 300mm is:

3.8m wide; 2m apart to provide for the plastic conduit arches every 2m. The layout must be in a rectangular shape, not trapezium or any other deformed shape. (See picture below)

Start by measuring the precise layout for the straight steel pegs. Remember, the tunnel must be positioned north-south in its length. This is to absorb sunlight equally in the tunnel.

Then lay the netting of 3.8 x 12m over and between the pegs. Then assemble the arches of 3 x 2m conduit pipes by joining them with the 200mm connecting sleeves. Lift the netting as you put the arches in place.

Once the arches are in place you stay the 2 ends with soft mild steel wire or any roping that will do the job.

It is important to notice that you should tie the end arches to the netting, along the seam, with wire ties of about 80mm long. Hold the net’s seam in place along the plastic arch and push the wire tie trough the netting, as close to the arch as possible, to avoid tearing of the net, every 1m.

Now you tie the stay wire to the arch, just below the connecting sleeve by pushing the wire end through the netting, around the pipe and back to the stay wire where it is wound loosely, to be able to loosen easily for future adjustments.

The reason why the stay wire is fixed here is to cause a ‘pinching effect’ on the arch, squeezing it slightly together, as the stay wires are trying to pull the arches downward when being tensioned. This should keep the arches in a neutral shape, not deformed downwards, or squeezed upwards.

The 2 stay wires should be fixed to one single stay of 12mm x 300mm, bent over at the top (hooked peg). The stay should be approximately 3m away from the base of the VT. This will help with the neutral shaping of the arch when squeezing up and pulling down onto it.

Use 2 hooked pegs to hold the netting down to the ground at the back end of the VT. Use 2 hooked pegs to hold the netting down at the front of the VT, where the zips start to open up from the bottom. These front panels will tend to pull up and flap when the zips are opened up.

 

 

 

 

Planting the Tunnel

 

Now you will be ready to plant the VT. Normally the planting bags (PB) are spaced from the back to the front in 3 rows of 4 – 6 – 4 PBs. This means that there will be 14 PBs from the back to the front of which 1 row will have 4 PBs, then a space or path to walk, then a row of 6 PBs, then a space or path to walk and then the 3^rd row of 4 PBs. (See picture below)

Each PB is specified as an 8 litre planting bag and should be filled with sand until 2cm from the top. The sand should be from a dry river bed or sand bank because the sand should be “sterilized” by the sun from fungus, pest and disease that may be present.

Obviously this sand has no feeding for the plants, but it is referred to as a “planting medium”, meaning that it is used purely to support the plant in its growing.

The feeding is done by mixing a hydroponic fertilizer into the water which is then used to water the plants.

 In most cases the PB is planted with 3 planting pods, equally spaced. You may choose to grow seedlings first, or to plant the seeds directly into one of the pods.

A seedling mix which looks very much like a ‘potting soil’ is placed into the pods. Each pod should not contain more than a table spoon full of the seedling mix. The seed is than planted carefully into the seedling mix, not more than 1cm deep.

Each planting bag with its 3 pods should be watered with clean water and no hydroponic fertilizer until it has germinated and grown about 2cm high. The seedling mix is food which the plant needs for this germination stage. Thereafter you must start to water the plant with the correct mix for each crop type. Instructions are normally on the bag.

Take care to water each bag with a 340ml Coke can and deliver the water carefully in the middle of the 3 young plants to seep away from the middle to each plant. If you are careless the sand around each plant’s roots will be washed away and the plant will die.

You should water the PBs at 07:00 in the morning and at 14:00 in the afternoon. Remember, the plants are growing and surviving from the food in the water only. The water will only last about 6 hours, which is why the PBs need to be watered at these times.

The crops that suits a beginner are Spinach, Onions, Beetroot, Carrots and some herbs such as Celery, Basil, and Thyme. Plant Spring Onion amongst Spinach and Basil amongst Cabbage to repel insects that will feed on the leaves of these crops.

 

 

 



 

Mixing the Hydroponic Fertilizer

In Namibia we are using a fertilizer called “Hygroponic Fertilizer” and it is supplied by Agri Grow in Windhoek.

The average, general mixing ratio is 900g of the Hygroponic Fertilizer into 1000 litres of water. This will do fine for most crop types planted in the tunnel. As you become more experienced you will start to read more about the crop types and what mix ratios will let then grow to maximum capacity.

There is a difference between the needs of leafy plants like spinach compared to rooty plants like carrots compared to plants like tomatoes. The NPK mix ratio of the fertilizer will address that.

You may even experiment with different manufacturers in your country, as long as they contain trace elements as well. Talk to the expert at a nursery close by. If they cannot help, ask for directions to someone who can. They are all over.

 

 

Drip irrigation

Drip irrigation makes it just so much easier to water the plants twice a day. It must be set up correctly though and it will challenge your technical skills as well as your budget.

The easiest way to do drip irrigation is by gravitation. This is where you put up a 1000 litre water tank right next to the VT on a stand of about 1.5m high. The height is necessary to create the pressure needed to feed the drip pipes and let the water drip as evenly as possible throughout the VT.

From the tank you will need a 60mm pipe which will have 14 T-pieces to feed the drip line for each of the 14 PB rows. Then you will need end-stops (a plug) to seal the ends of each pipe.

Then you fit the drip lines across each of the 14 bags, to cross over at the middle of each bag. These lines can be held in place with wire pegs of about 150mm long, hooked at the one end to keep the pipe over the PB and in place. Any other sensible way of keeping the drip lines in position will be good.

Then you pierce holes in the drip line pipe, on top, over the centre of each planting bag. The holes must not be too big or too small. A medium size needle should do.

Then you fit a tap or faucet where the water leaves the tank.

Close the tap and fill the tank with clean water. Turn the tap open and let clean water flow in the drip lines. Use a 340 ml Coke can at the beginning and end of each drip line to determine how long it will take to fill each one and to see if they fill up at the same time. Play with the tap position to find the best position for this. It is important to fill all these cans equally and to determine the time it takes. This is the time you will open the tap 06:00 in the morning and 13:00 the afternoon.

Then you close the tap and fill the tank with clean water. There should be no debris that will block the drip line holes. Add the correct amount of Hygroponic Fertilizer to the water in the tank and mix well. Leave the tank for about 30 minutes to give any solids pieces of fertilizer that did not dissolve to sink to the bottom of the tank. Now you open the tap to the position determined above for the time determined above at the given times. The plants should grow well.

 

 

Some more photos on Veggie Tunnels: