Hydroponic Crop Production – Tomatoes, Capsicums, Cucumbers, Lettuce.

December 4, 2016 Hansie Britz

TOMATOES

Tomatoes are one of the major food crops of the Western world, yet breeders are still trying to improve the fruit’s disease resistance, shape flavor and color. The tomato is a member of the Solanaceae family which also includes peppers, capsicums, eggplants, potatoes and tobacco. While many consider the tomato to be a vegetable, it is in fact a berry fruit. There are many varieties and they are used in many different ways. Some are eaten fresh in salads, others used in cooking. Some varieties are firm and have a large amount of fibre (i.e. they have a low solids content). Firm varieties are preferred for salads and sandwiches. Hence selection of the correct variety is important.

When deciding to start growing tomatoes commercially it is very important to find out what your market wants. If you are seeking to establish a new market then you should do some research into the market size. It is also important to produce quality fruit. The tomatoes should have a uniform color, and fruit showing uneven or blotchy areas should be discarded, as well as bruised, split or misshapen fruit.

Varieties

It is very important to establish the market you are intending to sell to and then produce for that market. While the grower may be proud to produce large prize-winning tomatoes, the normal consumer buys tomatoes that are 65 to 75 mm diameter and weigh 120 to 150 grams. Tomato varieties can be placed in four main categories according to their method of production and market use:

  1. Canning tomatoes.                                                
  2. Greenhouse tomatoes.
  3. Outdoor tomatoes.
  4. Specialty tomatoes. 

Spacing

Plants should not be crowded. Close planting tends to favor leaf diseases and development of smaller fruit. At the same time there must be room to work along the rows and the plants open enough to allow light to penetrate and air to move through the plants. The optimum space per plant is between three and four plants per sq. metre of growing area, and if rows are 30cm wide then the spacing per plant is 45cm or 23,000 plants per hectare with aisle widths of 900 mm in the greenhouse. The density of planting may be increased in spring to give 30,000 plants per hectare of shed.

Fruit Development

Fruit color development is also temperature sensitive, the best red color forms when the average daily temperatures are 18degrees C to 24degrees C. Yellowness increases as temperatures rises above 26 – 29 degrees C. If the temperature rises above 40degrees C, the mechanism for producing the red pigment is destroyed. The affected areas on these fruit are yellow or sunburnt. When the fruit is maturing it is best to reduce the amount of watering to minimize leaf spot damage, as well as fruit damage such as star cracks. Restricting watering also helps to improve the fruits’ keeping qualities.

Harvesting

All produce should be suitably mature when harvested. Maturity must not be confused with ripeness. Maturation can only take place on the vine, whereas ripening (fruit softening and color development) can continue on or off the vine.During vine ripening, sugars, acids and other flavors move into the fruit and the texture is improved. Tomatoes are ready for harvesting about three months after they are transplanted. Optimal color development for tomatoes occurs between 15 – 21 degrees C.

Tomatoes are harvested for the local market at the “breaker” stage which is when the blossom end shows a pink coloring. If you are supplying distant markets the fruit should be green but mature, i.e. the seeds will be fully developed and surrounded by jelly-like flesh that has just started to color, and the fruit surface is a light green color. In warmer weather fruit will need to be picked about two to three times per week; under cooler conditions fruit my be picked less frequently. The stems should be trimmed flush with the top of the fruit to prevent bruising during storage and transit.

CAPSICUMS

Capsicums also called “peppers and chilies” are a rich source of Vitamin C and Vitamin A. Green capsicums and red chilies have very high levels of Vitamin A; red capsicums are very high in ascorbic acid (Vitamin C). They are a warm season vegetable, requiring a relatively long frost-free growing period for maximum production and perfect for growing in a “tunnel farming” type of operation.

CUCUMBERS

During the last ten years continental cucumbers have grown in acceptance from being a novelty vegetable to a major vegetable crop in a number of areas. They are ideal for tunnel farming type of operations. The techniques used for hydroponic cucumber production often involve a poly-house – tunnel. This will protects the plants from rain, wind, hail, extreme temperatures etc.

LETTUCE

Lettuce is an indispensable part of most salads. It is a summer flowering plant which produces vegetative growth in the cooler months and flowers under conditions of long, warm days. In hot dry weather or when the plant is under stress the plant is inclined to run to seed. The gap between peak maturity and starting to run to seed may be as soon as one week. It is therefore very important to know exactly when to harvest to achieve high quality, well-developed lettuce. We can help in various aspects of setting up a profitable farming operation including farming plans, farming marketing plans etc.

CONTROLLING THE ENVIRONMENT

The major factors that influence plant growth are the interaction of the plants genetic makeup and the environment. The grower has very little control over the genetics of the plant but he can exercise some control over the environment. Most growers show no originality when looking to provide protection to their crops. They tend to move from growing outdoors without any protection to poly-houses which fully enclose their crop.

Windbreaks

The first stage in protecting crops is the use of a windbreak. The material used should allow air to pass through it and simply reduce the velocity of the wind. The barrier must be high enough and strong enough to do its job effectively. Many lettuce growers build windbreaks 7m or more in height, using commercial wind break fabric meshing. Other growers plant trees and bushes to reduce the effects of the prevailing winds.

Rain and Hail

Thew next stage is providing protection from rain and hail. This allows the grower to work with a degree of comfort and at the same time prevents the nutrient solution from being diluted or changed, resulting in crop damage. Many lettuce growers have installed clear plastic covers 5-6 metres above the crops, in the form of a pitched roof.

Temperature Control

In areas where frosts or low temperatures occur, full enclosures such as poly-houses (tunnels)  can be used to help maintain better growing temperatures. However, a problem with poly – houses is that humidity tends to increase and fungal diseases may be encouraged. Moisture condensation inside the poly-house can also lead to water droplets falling on the plants, particularly flowers, as soon as the shed starts to warm up in the morning.