How farmers grow vegetables in hydroponics

Friday July 05 2019

An agronomist explains how to plant tomatoes using hydroponics technology. Photo by Lominda Afedraru

Providing quality nutritive food to millions of people by 2025 will be a major challenge for Uganda.
Increasing population, decreasing land, water holding and global warming are some of the major impediments for agriculture, the backbone of this country. Various biotic and abiotic stress factors are threatening the open field agricultural production systems throughout the world in varying degrees.

The soil fertility status has attained almost the saturation level in most parts of the country as the productivity is not rising proportionally with the amount of inputs. With the infertility challenges, scientists across the globe, including those in Uganda have come up with a technology where farmers can grow a number of horticulture crops ranging from vegetables, fruits and flowers, among others in a greenhouse using hydroponics to substitute soil.

Papius Tumusingiize, an expert in agricultural convergence technology is lead investigator of the technology involving growing of tomatoes in smart greenhouse using hydroponics. According to Tumusingiize smart hydroponics system involves self-monitoring analysis of the greenhouse farm using a computer which is connected to technological systems inside and outside the green house. The green house has a system of censures which is connected to the computer.

“What the farmer needs to know is to engage a scientist to set the growing conditions for the plant in the computer,” says Tumusingiize.

Types of censors
Tomatoes grow best under optimal temperature of between 20 and 28 degrees Celsius which the computer will maintain.
Whereas the temperature outside may be so cold during rainy season below 16 °C or too hot due to heat rays at more than 35 °C, the solar radiation censors will control the temperatures automatically.

There is an exhaust fan installed to control the temperature as well, in case of high temperature the fun will automatically switch on to blow the excess condition. For cold conditions the aeration open outlets will close and for excess heat the shed net established inside the greenhouse structure and on top of it outside will automatically cover the structure.


There are also rain censors which control the conditions when there is a storm which may lead to destruction of the greenhouse structure. This is through an automatic closer of the open ventilators which are in most cases open to allow fresh air inside the greenhouse.

Another component is the installation of wind vane which will indicate the direction of wind flow and the anemometer used to measure the speed of the wind.

In case of too much wind, the computer will read it and the vent will close to avoid its entry into the greenhouse to avoid destruction of the structure and the plants.

Inside the greenhouse there are humidity and temperatures censors as well to regulate the condition inside. Another component of the greenhouse is the carbon dioxide censor used to measure the carbon dioxide rate meant for the plants for photosynthesis to take place.

“Greenhouses work on the principle of the greenhouse effects where the sunshine heats and sunlight penetrates the curtains and it is reflected back to produce heat. Too much heat in the greenhouse will cause wilting of the vegetables. This is the reason farmers must ensure they adopt the technology as it is with all the sensors connected to the computer,” Tumusingiize says. The computer has to be on all the time and in case of any power failure, there has to be back up generate to provide continuous source of energy.
Tumusingiize and team have set up two greenhouses at Kabanyolo each sitting on six by 54 metres but the space occupied by the tomato farm is five by 50 metres.

A farmer wishing to establish such a smart hydroponic greenhouse structure will need to part with $200,000 (about Shs700m).
However, there is a cheaper option where farmers can establish their hydroponics on a flat piece of land and simply tie strings for the plants to grow and run through on them for continuous harvesting.

The computer is powered by climate control panel machine specifically manufactured to regulate electricity flow in agricultural greenhouses. It reads the climatic conditions suitable for the plant growth and sends it to the computer.
At the moment the greenhouse structures are a demonstration site where farmers mainly from Wakiso District in Namulonge and those from Ssese Island have so far come around for sensitisation and lesson learning.

The scientists are purchasing a box of hydroponics with three seed planting outlets at Shs3,000 from Sri Lanka and from each box they are expecting 125 minimum tomatoes. The boxes are packed with sow dust which farmers can acquire locally.
It is fed through drip irrigation of a mixture of concentrate comprising Nitrogen, Phosphorous, Potassium, Magnesium, Calcium, Zinc and Baron. In case of another green vegetable such as strawberry the growth nutrient mixture is different.

Seed preparation
Tumusingiize categorises tomato seed as determinants which grow in four months and after harvesting the stalks are uprooted and replaced with new set of seedlings.
These include local varieties such as Tengeru and MT56 with one kilogramme sold at Shs350,000 each. Other varieties are Nenoveta and Galleria where each packet comprising 200 and 600 seeds goes for Shs50,000 and Shs60,000 respectively.

After transplanting continuous drip irrigation watering is required and this means constant water supply in the computerised tanks which are used to mix the nutrient ingredients which runs through connected pipes to hydroponic boxes. There is a water controlling machine used to regulate water usage in case there is water shortage, the machine will stop operating.

The yield of these varieties grown under this condition is so high because each plant is capable of producing 25 kilogrammes with minimum of 125 tomatoes in one harvest. Trellising is important because as the plant grows it has to be bend downwards and stretched to grow horizontally all the hydroponic structure for more fruiting to occur. One tomato plant measures 12 metres long for the one year season.