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 nutrient solution. Elements are actively [...]
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 factors such as: plant growth [...]
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 greenhouse cladding should be sprayed [...]
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 of the material. All insect [...]
Heat is always a problem in greenhouses during summer months and even during winter in some areas. Extreme high temperatures cause stress in plants and reduce yields, quality and increases pest and disease pressure thereby increasing costs. Overall, the economic viability of a greenhouse decreases if temperature is not controlled sufficiently. One of the latest [...]
The installation of new evaporative pads is expensive. The material should last at least two years if not more. With good regular maintenance, evaporative pads should last 5 years. Fortunately the grower has the opportunity to spend very little money on small items which will increase the lifespan of the evaporative pad. Considering the cost [...]
Pad-and-fan systems, also called evaporative pad-and-fan systems, is the most common method of cooling a greenhouse in warm weather regions. Although not optimal, it is better than no cooling at all. Using an evaporative pad-and-fan requires a fan mounted opposite the evaporative pads. Evaporative pad-and-fan systems are referred to as “pad and fan” systems because the [...]
Many growers have tried reducing temperatures (cooling) with fogging nozzles. The concept of spraying the air with microscopic water droplets which absorb the heat in the air sound right. However, fogging does not just decrease the temperature, it increases the humidity as well. A fogging system cannot operate efficiently if it does not have a very [...]
Ventilation of greenhouses in humid tropical areas presents the grower with a complete new set of problems. There are various methods available but none have the desired effect. Screening is limited since it can only be applied during certain periods of the day and it limits the amount of sunlight reaching the plants. Evaporative pads [...]
