A SUBSTRATE is the material in which the root system of the plant will develop. It can be solid, in which case it serves to anchor the plant; or liquid, in which case it maintains an appropriate balance of air and the nutrient solution.The minerals that the plant needs are dissolved into the water which is then watered directly to the plants.
So instead of the plants searching throughout the soil for their minerals, they draw them directly from the water that they are being fed.
The important factor in choosing a substrate is its availability, the proximity to the source, and the cost.
Some common substrates used in the tropical regions are sand, rice hulls (paddy shells) , grounded clay bricks, coconut fiber dust, charcoal dust , saw dust, grounded volcanic stones and water.
A good substrate must be capable of maintaining moisture and draining excess water, not degrade or decompose easily, not containing nutritive mineral elements , micro organisms harmful to man or plants, not be contaminated with industrial residual waste.
Recommended substrate mixtures include 60% rice, hull; 40% sand ; 60% rice hull 40% ground clay bricks ; 80% rice hull 20% saw dust or clean rain water.
In Guyana, where rice hulls are most commonly used, you can use a ratio of 2 buckets of rice hulls to one bucket of sand.

The open hydroponic production system:
A Hydroponic Production System “can be classified as “Open” or “Closed”.
In the Open System, the nutrient solution is mixed and applied by hand with a container to the plant as required.
This is the more common system in Guyana.
In the Closed System, the nutrient solution is re-circulated continuously by providing the nutrients that the plant requires in the water and by manually shaking up the water on a daily basis.
One can see an example of the Floating Root System at the St. Stanislaus College Farm at Sophia.
In the open system, lettuce, pakchoy, celery and other seedlings are transplanted onto a sand/paddy husk substrate.
The time from transplanting to harvesting depends on the vegetable species. However, as an example, you can harvest lettuce and pakchoy at about 28-42 days after transplanting, and celery about 40-56 days after transplanting.

Hydroponic Fertilizers:
Hydroponic fertilizers contain a balanced amount of nutrients to produce healthy and productive plants.
In general, the nutrients required by the plants are best grouped as major nutrients and minor nutrients. This production system revolves around the preparation and use of three concentrated solutions , made from combinations of major and minor nutrients.
The solutions are prepared for you by our Field Support Team.
For more information on fertilizers and application of fertilizers, speak to your Hydroponics Extension Officer.
Pest Management and Control:
Common insect pests of vegetables include spider mites, aphids, whiteflies, thrips, cutworms, crickets, beetles, leafminers, tomato hornworms, pinworms and bud-worms.
For the control of pests, use natural products such as hot pepper, garlic and neem. They are used to prevent infestation and have the following advantages: they are non-pollutant, pests do not develop a resistance to them, no special equipment is necessary to fumigate, they are easily made, they are economical.
For preparation of natural pesticides speak to your Hydroponic Extension Officer.

Costs and benefits
As indicated, a range of containers, such as old plastic washing tubs, children’s bath tubs, discarded plastic bowls, broken plastic containers, plastic oil or soda bottles with the tops cut off, small trays and plastic or concrete plant pots can be used for planting.
The cost of producing twelve lettuce plants is about $300, and this will mean a savings of $600-$900, based on normal market prices .
If you want to sell to neighbors and relatives, your return on 50 lettuce plants would be about $2750-$3750.
If after planting around the house you want to develop a small business using a hydroponics Shade House, talk to your Field Extension Officer (END).

(Article courtesy of HOME-BASED HYDROPONICS VEGETABLE PRODUCTION MANUAL By Kelvin Craig, Franklyn Harvey, Shaun Francis, Gavin Gounga, Panday Mansaram Sigmund McKenzie, Ryan Nedd. Partners of the Americas (Partners) / Caribbean Self-Reliance International (CASRI)

(By Clifford Stanley)