The effectiveness of a pad and fan system will not only depend on the design, but also on the wet bulb temperature outside the greenhouse. It is not the relative humidity, as many grower think that determine the effectiveness of the pad and fan system. The wet bulb temperature will [...]
Mechanical filtration is not an effective tool to prevent water borne diseases in NFT hydroponic nutrient solutions. It has been found that the total organic carbon content can reach 20 mg.L-1 for 2-3 months without affecting plant growth. There are many other compounds that attribute to the total carbon mass [...]
The correct flow rate of closed hydroponic systems is critical for optimal growth of plants. The flow rates are important for all types of closed hydroponic systems such as pure NFT systems, gravel cultures and ebb-and-flow systems. Inadequate flow rate will result in: Reduced oxygen levels at root surfacesIncreased susceptibility [...]
The pythium fungus is one of the serious diseases that growers can encounter in hydroponic systems. The disease can be kept at bay if the irrigation system can be closed of from the environment. The best method to control pythium and phytophtera is by maintaining a 2.5% concentration of hydrogen [...]
Many growers are under the impression that a maintaining a specific pH is essential to optimal growth and good yields. This is a misconception about the effect of pH on plant growth. The specific pH of the nutrient solution does not have a significant effect on plant growth or for [...]
Nutrient removal is quite often neglected in closed hydroponic systems since it is difficult to measure and control. The reason is that not all nutrients are removed at an equal rate by plant roots. The essential nutrients can be grouped into 3 categories based on the rate of uptake from the [...]
Refilling nutrient solutions are only required when a closed (NFT) system is used. With open hydroponic systems the nutrient solution is not re-used so no refill solution is required. Very little information is available on the subject and methods should be developed according to system design. Each system will have unique requirements because of [...]
Cooling a greenhouse can be just as expensive as heating, well almost. There are some very practical methods that you can use to save money. One of the cheapest methods are spraying the surface of plastic tunnels with soluble lime. Here is how. The surface of the [...]
Insect screens or thermal screens are designed to reduce heat in summer and increase temperatures during the night, but also to reduce the number of insects entering the production area. Various designs are available and each type is designed to keep certain insects out by varying the size of the holes and thickness [...]
