Covering materials protect crops from weather conditions, and influence greenhouse microclimate altering the growing conditions of the crops compared to the external climatic condition (Vox et al. 2010). Glass, semi plastics, and plastic films are the most common covering materials and are widely used. Nevertheless, those materials are rather unsustainable especially plastics since it is petroleum-based and energy losses through those covering material are high. Even so, replacing conventional plastics with biodegradable materials in agricultural applications does not reduce the amount of waste, but it does provide the opportunity to choose an alternative waste treatment strategy, i.
e. organic recovery (Kapanen et al. 2008). To increase the sustainability of the greenhouse, innovative covering materials should be applied along with effective heating and cooling systems. Biodegradable materials formed with raw materials of renewable origin have been developed in recent years to be used as environmentally friendly alternatives to petroleum-based materials.
For greenhouse cultivation good water quality is vital.
The plant material is always exclusive, and they cannot take any risks. Because water can only be re-used if it is clean, a reverse osmosis installation should be built, where water is fed into a special installation using membranes. This reduces water EC level and also removes any bacteria, viruses, and mold. Reverse osmosis leaves re-used water just as clean as rainwater, and therefore fertilizers can be applied more precisely. By using a combination of different technologies, it is possible to reduce water consumption by sixty to eighty percent.
Hydroponics is a technology for growing plants in media other than soil (substrate culture) or a nutrient solution (water culture) (Vox et al. 2010). The hydroponic system enriches the water with nutrients necessary for plants in a closed system, which protects the water from evaporating and prevents discharge to the outside environment (Roberto 2003). Hydroponic is necessary for the optimization of water and nutrient delivery to the plants to reduce water and nutrient consumption and drainage with groundwater and soil preservation. There are 6 basic types of hydroponic systems which are wick, water culture, ebb and flow, drip, nutrient film technique, and aeroponic. Hydroponics has many advantages, it eliminates soil-borne pests and diseases, increases yield, reduces crop maturation cycle, and crops and plants are free of chemical traces (Roberto 2003; Vox et al. 2010). There are also disadvantages but the most important one is the high capital cost. However, hydroponics is worth investing it aims to increase the sustainability of the greenhouse.
Irrigation has been researched intensively since the early 1950s. It became clear that water use is much more efficient when pressurized irrigation is used as opposed to surface irrigation. Pressure irrigation systems enable better control and monitoring of irrigation that can be translated into higher water use efficiency. In recent years, approximately 25% of greenhouses with soilless substrates have switched to recycled irrigation systems. Recycling the water and nutrients by reusing water drainage either back to the same or nearby field appears to be the most efficient, environmental, and economical solution: approximately 30% to 40% of water and fertilizer inputs are saved. Potential pollution of the aquifer by open irrigation systems is reduced. The switch to recycled irrigation systems increases yields. The water must be tested so the farmer may clear it of any organisms that can negatively affect the crop. The system has to be installed properly, otherwise, leaks and water loss can occur and lead to crop failure; the crops will suffer from this and may die. The pipes connecting the tank to the plants can get clogged with residues from unclean water due to the filtration process, so maintenance is essential. At their early stage, crops require at least 0.75 to 1 liter per plant, per day, and this increase at the blooming, fruiting, and harvesting stages (Smith, 2008). The availability of water is an essential requirement for the greenhouse growing of high-added value crops (Castilla & Baeza, 2013).
Working with modern technologies requires new skills. Agricultural extension service deals with three main fields: Instructing to provide updated agricultural knowledge for farmers, training to provide farmers with concentrated professional knowledge as a basis for adopting new and advanced technologies, and production of applied knowledge where agricultural extension service professional personnel conduct lots of experiments, observations and studies each year, to find solutions to problems that emerge in the field and applying them in the field. This way, the agricultural extension service makes available to farmers at the forefront of current information for use in the agricultural production process (Giacomelli, 2002). The fields of knowledge that the unit assists farmers in adopting include: efficient use of water, use of recovered and salty water, adoption of technologies and automation for personnel saving, improvement of agricultural product quality to meet international standards, variety diversification, reduction in the use of pesticides, advancement of agricultural subjects related to environmental protection, improving the image of agriculture and training a young generation to continue to work in their parent’s farms (Hanks, 1983).
The traditional greenhouse in the food production industry is very efficient when it comes to providing food for the majority of the population. However, it is extremely unsustainable and it is heading toward an inevitable end. When a traditional greenhouse is integrated with a sustainable system, the result will be a sustainable greenhouse. Integrated pest and disease management assure that pests and diseases are enemies of sustainability and that pesticides cannot be the only mode of dealing with pests and diseases. The natural enemy, sticky paper, black and white plastic mulching and insect-proof nets are being used as integrated pest management methods. The sustainability of greenhouse farming would also be assured if farmers can consider renewable sources of energy. The use of modern irrigation, the reduction of water EC level, types of irrigation, and recycling of water are considered determinants of sustainability. Technical training can also assure greenhouse sustainability through regular farm visits by extensional officers to enlighten farmers and also how training and workshops can be used to enhance knowledge among greenhouse farmers. The sustainability of greenhouse farming technology has been a worldwide challenge. The goal of the sustainable greenhouse is to reduce the usage of energy, water, and agro-chemical; and to minimize the amount of waste from the production.