Factors determining plant temperature in a greenhouse. Radiation or heat energy can be reflected, transmitted, absorbed, conducted, re-radiated or used to evaporate water. Evaporation requires more than 500 calories per gram of water evaporated. It is evident that if radiant energy is absorbed, plant temperature must increase until an equilibrium is reached at higher values. [...]
The protected greenhouse environment The greenhouse environment is designed to allow plants to perform close to their genetic optimum so that the grower achieves maximum profit. A greenhouse is designed so that the plant converts sunlight, water and CO2 and minerals into marketable yield. Thus the protected greenhouse environment creates a "cozy" climate inside a [...]
Heating the nutrient solution in order to increase growth rate can provide growers an edge over competitors. This applies to all business categories. Heating up the nutrient solution can be complicated and expensive and that is where the competitive edge is. Not every grower has the ability to implement the technology effectively. Heating the root zone [...]
Lets face it, lettuce is one of the fastest growing crops from transplanting to maturity. What makes it even more crucial is that the whole plant is harvested, unlike parsley or tomatoes where the harvest period can be extended. The great advantage is that more than one crop can be harvested per year, so staggering [...]
When it comes to fertigation programmes or recipes, most commercial growers have a good indication of what is required. The nutrient program is either obtained from the fertilizer company or it is a tried and tested custom mix. Quite often what these recipes do not indicate or provide, is the variations of nutrients required within [...]
Light and temperature are two crucial factors in greenhouse hydroponics. Plants use a very small range (only about 5% of visible light) in the total spectrum that is found in the atmosphere. The rest of the incoming radiation is not used in photosynthesis or for any chemical growth process. The range that a plant uses [...]
Temperature and humidity regime for peppers. Temperature and humidity go hand in hand. Quite often increasing the one has an effect of the other. So keeping a good balance can be difficult. The ideal temperatures at which peppers grow are between 18°C at night and 30°C during the day. The grower must make sure that [...]
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 [...]
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 [...]
Arid regions are characterized by low rainfall, low humidity and high temperatures during summer. The largest problem is temperature during the day time inside the tunnel during summer months. According to Arbel, Segal, et al. (1990), greenhouses found in arid areas have specific needs that should achieve the following: Low cost of construction and maintenance [...]
Root temperature does play an essential part in plant growth. It influences plant dry-mass, uptake of nitrogen, phosphorus and potassium. Root zone temperatures between 18–22°C lose less nitrate and phosphate through emissionsMiguel Urrestarazu, María del Carmen Salas, Diego Valera, Adrián Gómez & Pilar Carolina Mazuela (2008) Effects of Heating Nutrient Solution on Water and Mineral [...]
