Chapter 1: Install hydroponic system

Hydroponic farming presents a transformative approach to horticulture in Kenya, enabling efficient crop production with minimal land use and water consumption. As demand for high-quality vegetables and fruits grows in urban and peri-urban areas, hydroponics offers a sustainable solution that overcomes challenges such as poor soil quality and erratic rainfall. Installing a hydroponic system requires careful planning and design to optimize resource use and ensure healthy plant growth. This chapter explores the foundational aspects of designing, understanding, and selecting hydroponic systems suitable for Kenyan horticultural enterprises.

1.1 Designing hydroponic systems

Designing a hydroponic system means deciding, on paper and before any pipe is cut or tank bought, what will be grown, how much, where, and by which method the roots will receive water, nutrients and oxygen. The design fixes the capital cost, the daily labour, the water and electricity needed and the crops the unit can carry for years afterwards, so a mistake made here is expensive to correct later. Example: a grower who plans 2,000 lettuce heads a week for hotel kitchens and a grower who plans 400 tomato plants for a local market need different systems even if they share the same plot, because lettuce roots can sit in a shallow flowing film while tomato roots need a medium and a strong support structure.

A designer answers each of these questions before choosing a system:

• Crop and market: leafy vegetables and herbs are light feeders and suit shallow, water-based systems, while fruiting crops are heavy and need a medium, supports and more nutrient.
• Scale: a small unit of a few benches can be run by one person and fed by hand, while a large unit needs a pump room, a fixed layout and a daily routine for several workers.
• Site and climate: a greenhouse or net house gives shelter from rain, wind and direct heat, and the site must be level, drained and clear of dust and chemical drift.
• Water source: borehole, piped or harvested rain water is tested before the design is fixed, because salty or hard water limits the crops and the nutrient mixes that can be used.
• Power and back-up: pumps and air pumps stop when power fails, so the design either avoids pumps (a wick system) or includes a stand-by supply such as a small generator or solar battery.
• Skills and money: a simple system run well gives a better result than an advanced system run badly, so the design matches the skills of the people who will operate it.

1.1.1 Definition of hydroponic system

A hydroponic system is a way of growing plants without soil, in which the roots take water and all the mineral nutrients from a nutrient solution (water with dissolved fertiliser salts), either with the roots hanging directly in the solution or held in an inert medium that is fed with the solution. The system supplies, in place of soil, the four things soil normally gives a plant: support, water, nutrients and air at the roots. Because the grower controls every one of these, the crop can be fed exactly, grown in a small space and kept free of soil-borne diseases, but it also depends completely on the grower: if the pump, the mixing or the checking fails, the plants suffer within hours.

Components of a hydroponic system

• Nutrient solution reservoir: a closed, opaque tank that stores the water and dissolved nutrients; light is kept out because it grows algae.
• Growing medium or support: an inert material such as coconut coir (cocoa peat), perlite, pumice or rockwool, or net pots and float boards, that holds the plant upright and keeps the roots in contact with the solution.
• Delivery system: pumps, pipes, drippers, channels or wicks that carry the solution from the reservoir to the roots.
• Root-zone aeration: an air pump and air stones, a thin film that leaves the upper roots in the air, or periodic draining, so that the roots can breathe; roots without oxygen rot.
• Support structure: benches, frames, channels or troughs, and strings or stakes for tall plants, built to take the weight of the full crop and to give workers easy access.
• Control and monitoring tools: pH meter, EC (electrical conductivity) meter, thermometer and a timer, used to keep the solution in the range the crop needs.

Characteristics of hydroponic systems

• Soilless growing: the absence of soil removes soil-borne pests and diseases and the need for soil sterilisation.
• Efficient use of water: in recirculating systems the solution is used again, so much less water is lost than in field irrigation.
• Controlled feeding: the grower changes the nutrient mix to suit the crop and its stage of growth.
• Small area: plants can be grown on benches or in stacked tiers, which suits farms with little land.
• High dependence on equipment: pumps, timers and meters must work every day, and the grower needs the skill to read and correct the readings.

1.1.2 Importance of designing hydroponic systems

A good design makes the whole enterprise cheaper to run and easier to manage, and a poor design cannot be rescued by good management. A system with channels that slope the wrong way, a reservoir that is too small, or a pump that is too weak causes uneven feeding, wasted water and stressed plants from the first day. Careful design also reduces the cost of mistakes, because it is far cheaper to change a drawing than to dig up a floor or replace a length of pipe.

• Saves water and fertiliser: the right tank size and flow rate lets the solution be reused with little loss.
• Improves yield and quality: even feeding and even spacing give plants of uniform size, which is what hotel kitchens and supermarkets ask for.
• Lowers disease risk: a layout that drains fully, keeps roots out of stale water and allows cleaning between crops reduces root rots.
• Makes work easier: benches at a comfortable working height with clear walkways speed up checking, gapping and harvesting.
• Allows growth: a design that leaves room for extra channels, a second tank and more power allows the unit to be extended without rebuilding.
• Protects against failure: planning for a power cut, a blocked pipe or a burst joint (a stand-by pump, a spare timer, a float valve) limits the loss when something fails.

1.1.3 Types of hydroponic systems

Hydroponic systems differ in how the roots meet the nutrient solution: floating in a tank, in a thin flowing film, fed drop by drop, or fed by capillary action through a wick. The choice depends on the crop, the budget, the power available and the skill of the operator, and it is made before the unit is built.

1.1.3.1 Deep water float system

In a deep water float system, also called deep water culture or raft culture, plants sit in net pots set in holes in a float board (a sheet of food-safe polystyrene or similar material) that floats on a shallow tank of aerated nutrient solution, so the roots hang in the solution. An air pump and air stones bubble air into the tank, because still water holds too little oxygen for roots. The system suits fast-growing leafy crops such as lettuce, and herbs such as basil and mint, and the whole crop can be moved along the tank as it grows.

• Main parts: tank or pond lined with food-safe material, float boards, net pots, air pump with air stones and tubing, and a cover or lid that keeps light off the water.
• Strengths: simple to build, low running cost, a large volume of water that changes slowly in pH, EC and temperature.
• Limits: needs a constant air supply; warm water holds less oxygen; a root disease spreads quickly through the shared tank; heavy fruiting plants are not suited.

1.1.3.2 Nutrient film technique (NFT)

In the nutrient film technique, a thin film of nutrient solution flows along sloping, closed channels, and the lower part of the roots sits in the film while the upper part stays in moist air. A pump lifts the solution from the reservoir to the high end of each channel, gravity carries it along, and the solution returns to the reservoir to be used again. The channels are fitted with holes for net pots, and the plants are usually leafy vegetables, herbs and strawberries.

• Main parts: reservoir, submersible pump, supply pipes with taps for each channel, channels with a gentle fall (about 1 to 3 cm for every metre of length), return gutter and support frame.
• Strengths: very small quantity of water in the channels, easy to see the roots, light to build, good for tight spaces.
• Limits: depends on a working pump, because the roots dry within hours when the flow stops; channels can block with roots; plants at the end of a long channel can receive a weaker solution, so channel length is kept short.

1.1.3.3 Drip

In a drip system, a pump controlled by a timer sends the nutrient solution through small-bore tubing to a dripper (emitter) at the base of each plant, which grows in a pot, bag, trough or slab filled with an inert medium. The medium holds the roots and a reserve of solution between irrigations. Drip systems are used for fruiting crops such as tomatoes, cucumbers and peppers, which need support and a larger root zone. The system can be run to waste, where the drained solution is not reused, or recirculating, where the drained solution is collected and returned to the tank after it has been checked.

• Main parts: reservoir, pump, timer, filter, main line and fine tubing, drippers or drip stakes, containers with medium and a drain or collection gutter.
• Strengths: each plant receives the same dose, suits large plants and different spacings, and the medium forgives short interruptions in power.
• Limits: drippers block and need a filter and regular flushing; salts build up in the medium and are checked through the drain water; a run-to-waste system uses more water and fertiliser and produces waste solution that must be managed.

1.1.3.4 Wick

A wick system is a passive system with no pump and no electricity. A wick of cotton or nylon cord runs from a reservoir below the plant into the medium around its roots, and the solution rises through the wick by capillary action (the same effect that makes a lamp wick or a towel draw water upwards). It is a very simple hydroponic system and suits small plants with low water needs, such as lettuce seedlings, herbs and spring onions, and it is often used for training and for small demonstration units.

• Main parts: container or tray for the plant with medium, wicks, a reservoir or tank under the container, and a lid to keep out light and insects.
• Strengths: very low cost, no moving parts, no power needed, and almost nothing to break.
• Limits: the wick cannot lift enough solution for large or fast-growing plants; salts can build up in the medium; the system is small and slow to adjust.

Comparing the four systems

Chapter Summary

This chapter explored the fundamentals of installing a hydroponic system, beginning with the design phase where the concept and significance of hydroponic systems were defined and explained. It emphasized the importance of careful design to optimize plant growth and resource efficiency. Various types of hydroponic systems were examined, including the deep water float system, nutrient film technique, drip system, and wick system, each with unique features suited to different farming needs. The chapter then detailed the practical steps involved in setting up these systems, focusing on the correct assembly and installation procedures. Lastly, it addressed the ongoing maintenance required to ensure system functionality, such as monitoring nutrient levels, preventing blockages, and managing water quality to sustain healthy plant development. These components collectively provide a comprehensive guide for successful hydroponic farm management.