To study the protected structures – care and maintenance

Horticulture Guruji

Exercise 8

To study the protected structures – care and maintenance

HORT 222

Bed or bench preparation:-

Most of the flower crops are either grown in raised beds or in metallic benches. Orientation of beds should be towards the length of the greenhouse so that 45-60% of floor area can be utilized. In the modern greenhouse, moveable benches are used. By adopting a tier system in the greenhouse, the maximum area can be utilized for cultivation.


Soil is the natural growing medium for most of the greenhouse from economical consideration. But it has drainage and pest and disease problems also. Other media are also common in use. Recently, soilless media like rock wool, perlite, and cocopeat are common. Rock wool is made from basalt and limestone and is widely popular in western countries. Cocopeat is a natural media from coir pith. A good medium must be stable and has optimum bulk density and pH range of 5.4-6.0 for soilless media and 6.2- 6.8 for soil media. Media should have a CEC of 20-50 mol/kg.

Green House Cooling

The inside temperature of a greenhouse will be at least 5-100C higher than that of the outside temperature if it is not cooled. Cooling can be achieved in different ways.

1) Ventilation

Ventilation helps to keep the greenhouse cool and it removes water vapour transpired by plants and ensures acceptable RH. Ventilation replaces CO2 also. In a ventilated greenhouse during bright sunlight, the CO2 concentration in a crop canopy can be reduced below 30 ppm compared to 360 ppm in external air. If natural ventilation is relied upon, 20-50% of the floor area is provided as side ventilation openings. A greenhouse with openings on roofs can also be used. A greenhouse with fully open roofs can keep the inside temperature just 1-20C above outside in cold seasons. Roll up inside curtains can be installed on 2 or all 4 sides.

 2) Roof Shading:-

The amount of radiation energy entering the greenhouse can be reduced by applying opaque materials directly to the cover or by placing wood or aluminum lath or shade nets over the cover. Commercial shade paints are also available e.g. Redusol Xtra, variclear, Lime.

Retractable thermal screens are now used in high-tech greenhouses. These can be automatically stretched over the greenhouse, when needed.

3) Evaporative Cooling

Two types of evaporative cooling systems are there.

a) Fan and Pad Cooling System:- Here a wet cooling pad is kept at one end and a fan art another end. All vents in the greenhouse should be closed before running the system. The fan sucks hot air out of the greenhouse creating a negative pressure inside which draws in outside air through the cooling pad. As the pad is kept wet, water will evaporate and air will enter with a low temperature. This system lowers the inside temperature by 100C provided humidity outside is low. The limitation is that the distance between the pad and fan should not exceed 40 m.

b) Mist system:- Air is blown into the greenhouse through nozzles. This nozzle creates a mist of tiny droplets that should evaporate before reaching the crop.

Green House Heating

Heating is required in places where the temperature is very low. Heating can be done by hot water, steam, oil burners, or by electricity. In high-tech greenhouses, IR heaters are the most economical.

Irrigation and Fertigation:-

The automatic watering system through drips or overhead foggers is generally used depending on the crop. Fertilizers are applied with irrigation water mostly. This avoids wastage of water and fertilizer and reduces cost.

Choice of cultivar:-

In India major demand is deep in colour and it changes with season and occasion. Colour productivity, disease resistance, vase life, growth rate, market demand, and other special characters must be looked into consideration.

Carbon dioxide enrichment:-

CO2 enrichment accelerates vegetative growth, water use efficiency, and photosynthetic capacity leading to high-quality blemish-free blooms, For CO2 enrichment, CO2 generators and injectors are used.

Ideal CO2 concentration for important flowers


Ideal CO2 Concentration (ppm)

Toxic CO2 Concentration (ppm)














References cited

  1. Commercial Fruits. By S. P. Singh
  2. A text book on Pomology, Vol,1. by T. K. Chattapadhya
  3. Tropical Horticulture, Vol.1, by T. K. Bose, S. K. Mitra, A. A. Farooqui and M. K. Sadhu

All Types of Horticultural Crops