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Although winter is a lull in outdoor farm work, there is certainly plenty of work to be done in sheltered spaces, most notably greenhouses where the production of a particular crop can be done regardless of the weather.
Protected areas are all means of protecting plants from adverse climatic conditions, allowing them to be produced in a specific area and in time, while this cannot be done outdoors. The purpose is to preserve heat that accumulates from the sun’s light energy or is introduced by heating systems.
Regulation of vegetation factors: T, relative humidity, lighting, CO2
Depending on the type and equipment, in them, it is possible to regulate to some degree individual vegetation factors, from temperature, relative humidity, duration and intensity of illumination, the concentration of carbon dioxide (CO2), etc.
Greenhouses continue to produce vegetables and ornamental plants from sowing, to planting and harvesting
Greenhouses are very useful in agriculture because they protect the plants from frost, thus extending the growing period of a particular crop, the production of planting material (seedlings of vegetables, rooting cuttings), and the production of vegetables and ornamental plants from sowing, planting all the way until harvest. In the growing of vegetables during average years, without extreme temperatures, ie long periods of high humidity or strong attack of diseases and pests, the same results can be achieved in the so-called premises. domestic craftsmanship as well as in contemporary facilities.
Advantage of protected spaces with microclimate control systems
Such years are, however, increasingly rare, and for some time now, protected areas with a microclimate control system have the advantage of reducing (increasingly extreme) and adverse external conditions. The organization of greenhouses and similar protected areas give farmers some security and continuity of production, which in the end, in certain market conditions may result in greater profitability.
For profitability and economy, the significant shift of plant species is needed
For the profitability and economy of the latter, we know that the change of plant species during the year is significant, and the choice of vegetable type and production time are conditioned by the type of protected area: low tunnel, high tunnel, greenhouse. The heating method is also indispensable, as is the climate, ie the possibility of selling. Compared to the continental region, due to the favorable climatic conditions in the Mediterranean, the use of unheated protected areas is extended by 15 to 30 days in the autumn, that is, it starts just as early in the spring.
Vegetables with less light and heat requirements are grown in the autumn and winter when the highest number of cloudy days is, and vegetable species with higher light requirements are grown in the spring and summer-autumn. So-called heat-loving types of tomatoes, peppers, zucchini, eggplant, while in the other case, lettuce, spinach, young onions, fenugreek do not need heated spaces and are grown as winter crops.
In protected areas, it is mandatory to grow in a row
In protected areas, it is obligatory to grow in a plot that represents the spatial and temporal alteration of the cultivated crops on a certain surface. Repeated cultivation in the same area should take at least three years, and the cultivation of vegetable crops from the same family, one after the other, should be avoided.
Due to the intensive production, ie the rapid change of crops in the protected area, and the demands of the market, it is sometimes difficult to comply with those rules. Non-adherence to the latter often leads to the accumulation of specific diseases and pests, the unilateral use of nutrients and, consequently, to a decrease in the quantity and quality of the yield.
The most notable greenhouse pests: aphids, Greenhouse whitefly, red spiders, Western flower thrips
Some of the most notable pests in the protected areas are aphids, moths, Greenhouse whitefly, Western flower thrips or red spiders. In the latter, the mentioned pests attack more plant species, and protection against them is done mostly by chemical means. However, biological protection and the use of natural enemies of pests have been successfully developing for some time now.
Diseases occurring in greenhouses and other protected areas are quite a few Rose powdery mildew [also known as ‘Weeping Mildred’], common pin mold or grey mold. It is ungrateful that they are transmitted from species to species, and their appearance is conditioned most by the temperature and humidity of the air, or (in) the possibility of regulating them, and the poor hygiene of the space is not negligible. When an infected plant is noticed, it should be removed and destroyed as soon as possible, and in no case should its remains be brought into the soil by cultivation.
Disinfection preferably at least once a year at the end of the growing season or in early spring
It is advisable to disinfect the protected area at least once a year, at the end of the growing season, ie after clearing the premises and in the early spring before the production cycle. The cleaning is carried out with benzoic acid or other disinfectants authorized for veterinary or agricultural use.
When it comes to the types and purpose of protected areas, it should be noted that there are low tunnels 15 to 25 inches high and 20 to 40 inches wide. They consist of arch-bent supports over which foil or agro textile is placed, while arches are dug up to 6 inches into the ground at a distance of 40 inches.
Low tunnels are most commonly used for the production of transplants
Low tunnels are most commonly used to produce bare-root transplants and as a protection against late spring frosts of crops planted outdoors. The foil is buried in the tunnel on the north side and attached to its surface from the south side. Thus, it rises more easily for ventilation during the hottest part of the day, ie when the outside temperature reaches the maximum required for the growth and development of the cultivated crop. A polypropylene binder is used to hold the foil during low tunnel ventilation diagonally strained between the arches.
Ventilation ends three hours before sunset
Low tunnel ventilation ends up to three hours before sunset in order to preserve enough heat for the plant from lower nighttime temperatures. High tunnels up to 70 inches in height, or between 80 and 170 inches high, are an integral part of agricultural production. They are constructed with aluminum or galvanized pipes (or profiles) like arches. For greater strength, the arches, are placed at a distance of 60 inches, while they are interconnected by galvanized wire or fittings and pipes. The foil is stretched over the arches and buried in the ground, and its ventilation is using the front sides. Due to the low ventilation capability (front side only), tall tunnels should not be longer than 80 feet.
High tunnels are best laid 14 days before sowing or planting
It is best if they are planted at least 14 days before sowing or planting to keep the soil warm. The tunnel can temperature protect plants up to 26 °F and the crops grown in it are protected from the weather in the initial growth phase, which shortens their time from sowing, planting until harvest.
The tunnels protect against frost and extend the harvest period in the fall
The tunnels protect the cultivated crop from late spring frosts, and by sowing or planting it can extend the harvest period in the fall. Cultures that do not require much heat overwinter in the tunnel, that is, they can be grown in winter. Apart from the latter, greenhouses are also important in agriculture as permanent and stable protected space covered with polymeric materials in the form of films or plates, or glass.
Today’s greenhouses are made of hot-dip galvanized steel tubes and aluminum profiles
Their construction is mostly made today of hot-dip galvanized steel pipes and aluminum profiles. Compared to the materials used earlier for the making of their construction (wood, concrete), the advantage of steel is that it narrows profiles, which reduces the shading of plants, and is easier to maintain and longer. Wooden load-bearing structures are suitable for home gardens because they can be made independently, and are still commercially used by manufacturers. Their main disadvantage is the easy breakage in case of heavy snow and the inability to belt with automatic heating and ventilation.
Greenhouses with emergency heating only at 25 to 17 °F
Greenhouses without heating or with so-called emergency heating can be used when the outside temperature is not lower than 25 to 17 °F, which allows sowing and planting in early March for less sensitive species, or early April for heat-loving crops.
In the fall, such facilities can be used until the end of November, and winter crops can be grown there. Heated greenhouses are used for the winter-spring production of heat-loving species and for the production of transplants that are planted in an unheated, sheltered space or outdoors. In the protected areas, mulching of the soil and direct covering of the crop with agro-textiles are also applied.
Mulching soil for better cultivation and care of vegetable crops during vegetation
Mulching the soil or covering it with polymeric but also with organic materials (straw, hay, shredded maize) is an agro-technical measure to improve the growing conditions of plants and facilitate the care of vegetable crops during vegetation. Applying black, transparent and translucent (photoselective) films, the soil temperature increases, which directly affects the faster growth of plants, early ripening of fruits, increase in yield and quality.
Black foils for winter and white for summer vegetables
Black foils are used in winter and early spring cultivation (lettuce, peppers, tomatoes, cucumbers, cabbages), and white and black-and-white films with the white side facing up can be used for crops grown in summer.
First of all, in order to reflect as much sunlight as possible and prevent the ground temperature from rising above the optimum. Mulching the soil reduces water loss, reduces erosion and reduces the leaching of nutrients into deeper layers of soil and groundwater. Before placing the foil, the soil should be well prepared and shredded in order to achieve the best contact between the foil and the soil, which contributes to its better heating. Laying of the foil, manually or machine, is done seven to 10 days before the planned planting, and the foil on the surface should be strained with a slight fall towards the edges, which are buried in the ground.
When setting mulch, the soil should be optimally moist above 50 °F
When setting mulch, the soil should be optimally moist above 50 °F, and in combination with mulching, drip irrigation is most commonly used. This system is placed under the mulch, which can also provide nutrition, ie fertigation. Thus, water and nutrients are added in optimal quantities near the roots of the plants.
Placing agro textiles over crops behind sowing, planting or later in vegetation
One of the agro-technical measures is the direct covering – that is, the placement of agro-textiles (fibrous material) over the crop, just after sowing, planting or later in vegetation. Unlike mulching the soil, where the material should be strained and properly adhered to the surface, when directly covered, the material is placed lightly on the surface of the soil or crop, as it raises and carries it during its growth.
The edges should be buried or fixed to prevent wind detection, adding that the purpose of such direct cover is to reduce vegetation by 7 to 15 days. Primarily due to the increase in temperature under the covers and the partial protection from the cold, heavy rain, hail, damage caused by birds, harmful insects such as lice, which are also carriers of the virus.
Under agro textiles, plant growth is accelerated
Below the agro textiles, we also notice smaller temperature fluctuations compared to the crop without cover, which accelerates plant growth. In the case of the agro-ethnical measure thus applied, water during rainwater slowly passes through the micropores on the fabric and moisturizes the plants and soil evenly. Afterward, it gradually dries and does not produce crusts. By keeping the water in the micropores of the agro textile, a thin ice crust is created when the temperature drops, which prevents it from falling further below the fabric. Detection is done in warm, windless weather when the maximum temperatures below the agro textile reach the maximum required for clearing.