Salads in greenhouses

Nowadays, the trend of demand in the international fruit and vegetable market is oriented towards the production of fresh and quality vegetables; farmers and the fruit and vegetable companies can answer to this demand with two solutions: providing the quality asked for by the fruit and vegetable market and elevating the production and the productivity of their fruit and vegetable products.
These two requirements can occur through the use vegetable cultivations in protected environments: technology, in fact, today provides knowledge and tools that allow an almost complete control of the cultivation conditions in order to obtain productions of fresh vegetables and salads suitable to the demand of the fruit and vegetable market.
Today,growing fresh vegetables is no more possible only in the warmer time of the year: cultivations in greenhouses, in fact, can extend the planting and harvesting seasonthroughout the year, including winter. The vegetables cultivated in greenhouses have undoubtedly higher costs compared to those grown in open fields, but the have considerable advantages: they allow also to save money, are of a superior quality in shapes, dimensions and colours, as growing conditions are more controlled and pesticedes are not used; furthermore the harvesting period of each variety is significantly extended, including salad and its numerous varieties.
The cultivation of salad in greenhouses has begun to increase in the European fruit and vegetable sector in particular: greenhouses consist of tunnels, formed by iron supports covered with plastic sheetings, unheated or heated. They permit to grow salad and vegetables in record time, while protecting crops from cold and snails, and ensuring the aeration of crops thanks to a perfored sheet.

Usually, the cultivation of salad in greenhouses is done in winter, while in spring gives way to other fruit and vegetable products, such as tomatoes and peppers.
In Italy in 2002, 3,456 hectares of land wer used for the cultivation of salad in greenhouses, which provided a total production of 113,873 tons of salad ad a harvested production of 110,480 tons.
Climate, even if not the only one, is certainly a factor which strongly influesnces the cost of the production of salad and production of vegetables by producers andfruit and vegetable companies: the cultivation of salad in greenhouses (as of other fruit and vegetable products) is an excellent solution to overcome this difficulty, as greenhouses give to the farmer or to the producer of salad the chance to control temperatures.
The current situation of greenhouses in Europe leads us to consider the need to improve the production structures and create structures that can manage anc control climate.

Production techniques in protected environments (greenhouses) differ a lot from those typical of the open field cultivations, as in greenhouses the environmetn can be modified in order to maximize the productivity of crops.

In Central and Northern Europe the predominant trend is towards a total control of the environment in greenhouses in order to achieve the potential production of the crop. As a consequence, the evolution of greenhouses took place in parallel with the onset of advanced technology systems (computer air conditionig, , hydroponic cultivations and robotics).
Otherwise, in countries with Mediterranean climate, the widespread presence of greenhouses characterized by lightweight structures has led to the development of cultivation techniques that enhance the adaptation of cultivations to a sub-optimal and only partially controlled environment.. In these areas, as there is less control of the greenhouse environment, the cultivation itself plays a predominant role in the microclimate, defining it through gas exchanges.
Among the means used to protect cultivations of salad in greenhouses from climate adversities, the greenhouse is certainly the best mean that can be adopted, as it offers the best opportunity of isolating the plants of salad from the external environment, by a more or less complete conditioning of the internal climate: : recently, in the constant research and experimantation t improve productivity of the cultivations in greenhouses, photovoltaic instruments, for example, have been very successful, allowing many farmers, producers of salad and fruit and vegetable companies to follow the development of certain fruit and vegetable products, among which stand out the production of salad, using innovative engineering solutions such as photovoltaic systems.
Always in the field of control of temperatures and climate as to the cultivations of salad in greenhouses, in addition to what was said on photovoltaic systems, other useful tools include heating systems (radiators, heaters, air heaters, gas stoves, etc.), cooling systems for cultivations of salad (windows in the side walls and on the roof to allow air exchangeby natural or forced ventilation, shading nets or sheets, cooling systems through heat pumps, etc.), the use of windbreaks, useful to reduce heat losses by conduction through the walls in case of cold winds, systems for moisture control and finally systems for the control of lighting og the cultivations of salad produced in greenhouses.
As to the cultivation of salad, the most widespread varieties for the production of salad in greenhouses are:

• BATAVIA FUNSONG SALAD: variety of gentilina lettuce for greenhouses, for fall, winter and early spring harvesting. It is a flexible, hardy and very productive plant od salad even in cold conditions and low light. It has an elegant, open and bright green head, The bottom is tight and has a very small core. This variety of salad has a high resistance to the adversities and parasites. It suits well to the fresh fruit and vegetable market.
• BATAVIA CANASTA SALAD: variety of batavia lettuce suitable to spring, summer and fall harvesting in the open field and to winter harvesting in greenhouses. It is a very productive plant of salad, with a large adn thick foliage and an intense green head with red margins, sweet and cris. It is suitable to the fresh fruit and vegetable market.
• BAGLIN HEAD SALAD: head lettuce for greenhouses suitable to winter harvesting. It is a plant of salad with an excellent weight and a high volume, an elegant posture that permits considerable uniformity at the time of cutting. The intense green head is semi-open, with an excellent heart, It suits both to the fresh fruit and vegetable market and to the 4th range production of salad.
• ROMAN SELE LETTUCE: variety of Romanlettuce for greenhouses auitable to harvesting from fall to late spring. It an erected and elegant plant of salad. Leaves are bright green,blistering, hardy and crisp. The head is compact and heavy with a large bottom and tight. It suits well to the fresh fruit and vegetable market.
• ROMAN PRESIDENTIAL LETTUCE: variety of Romanlettuce suitable for spring, early summer and fall harvesting in open fields and for spring and fall harvesting in greenhouses. It is andercted and elegant plant of salad that is uniform at the time of cutting. Bright green leaves are hardy and blistered. The head is open and heavy, full inside and voluminous. This variety of salad has a high resistance to adversities and parasites. It suits to the fresh fruit and vegetable market.
• ROMAN VOLTURNO LETTUCE: variety of Roman lettuce for greenhouses suitable for winter harvesting. It is and erected and elegant plant of salad Its light green leaves are almost smooth and velvety. The head is compact with a large and tight bottom. It suit to the fresh fruit and vegetable market.
• ROMAN SIVNA LETTUCE (LS8865): variety of Roman lettuce typical of southern Italian tradition, suitable to late fall, early winter an spring harvesting in open field and to winter harvesting in greenhouses. It has high prouction leves and a high resistance to over-ripening. It is a plant of salad with a high posture, dark green, hardy and blistered leaves. The head is very heavy and voluminous with a semi-open heart, full inside. It suits to the fresh fruit and vegetable market.