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Optimizing greenhouse environment for cut flowers

Post by on Wednesday, September 15, 2021

First slide
 The concept of greenhouse nowadays is emerging in the floriculture industry for cut flower purposes as the greenhouse has many advantages including the protection of crops from adverse climatic conditions.
Greenhouse provides a crop with optimum environmental conditions for proper growth and development of a plant which in turn helps to get a required length of flower stalk, bloom size and other related aspects of flower creating the conditions fit for cut flower.
The most important environmental conditions which influence plant growth, development and flower quality under protected conditions include light, temperature, humidity, CO2 enrichment and pest management.
Duration of light as well as intensity of light influences the quality of flowers. Light is directly related with photosynthesis and is correlated with carbohydrate content of the flower.
        The successful bud opening and vase life of a flower after detaching from a parent depends, to a greater extent, on the amount of carbohydrate content. Besides this light influences the colour of flowers as well.
The low unusual shading in roses leads to petal bluing, the high light intensity causes the problem of leaf drop, leaf spot etc. So, optimum light intensity is necessary for both plant growth and development as well as for flower quality.
        Optimum temperature in the greenhouse for cut flower production plays the most important role as the low or high temperature deteriorates the quality of a cut flower.
The physiological processes under high temperature are disturbed as it leads to loose carbohydrates accumulated in the tissues. Apart from this it causes a great water loss from the plant and thus growth and development is checked.
        The optimum humidity should be maintained in the house as it directly as well as indirectly influences plant growth and development. The requirement of the humidity however varies from crop to crop.
In carnation the plants perform well up to humidity of 50% and above this it causes physiological disturbances to the plant. In orchids a central tank is maintained with water to raise the humidity as these need minimum 30% night and 80% day humidity for proper growth and development. Likewise gerbera and anthurium are humidity loving crops.
CO2 enrichment:
        It is one of the most important factors influencing plant growth and development. CO2 level means the rate of photosynthesis. The involvement of CO2 at higher levels but below the toxic level enhances photosynthetic activities of a plant.
The other benefits of CO2 fertilization in the greenhouse are culture time shortening, reduction of blind shoots, excellent growth of laterals, earliness etc. Plant continues to develop when the CO2 level is maintained above the 300ppm present in outside conditions.
In rose the number of blind shoots is decreased, stem length increases and the number of petals increases besides shortening the time period of the crop.
In chrysanthemum the formation of thicker stem and flower is observed. Carnation yielded 38% more and enhancement of flower weight and stem strength is observed with the supplement of CO2. The gap from vegetative to reproductive period is reduced by two weeks. Besides this, cuttings of better quality are obtained.
In orchids bract diameter as well as size and quality of bloom is enhanced with enhanced levels of CO2. The overall view is that the quality of produce is obtained excellent by the CO2 fertilization in the greenhouse.
How to fertilize CO2:
       The CO2 should be fertilized one hour after sunshine and before sunset as it is a time when plants can utilize it in the presence of sunlight. The ventilators and exhaust fans should be kept off at the time of CO2 fertilization.
Incomplete combustion of the gas should be checked as this causes the problem of ethylene and CO which are harmful to plants. The harmful effects are shortening of internodes, branching increases and flowers becoming distorted. The upper limit for CO is 50ppm & gas should be sulphur free.
Growing media:
        The media should be well aerated, sterilized, free from insect pests and physiologically inactive. Excess saline or chlorine is detrimental for crop growth. The media for growing crops can be soil, sand, perlite, peat, coca peat, coconut husky, straw husks, vermiculite etc. The soilless growing media should have the following properties:
•                   It should hold the plant well.
•                   It should be physiological inactive.
•                   It should have excellent water and nutrient holding capacity.
•                   It should be well drained.
•                   It should be well aerated.
Pest management:
        Pest management plays the most important role in quality flower production as these cause considerable loss of produce. The concept of pest management is to keep the population of insects and disease below the damage level.
The cultural methods include use of resistant varieties, sanitation, proper spacing, water management, planting trap crops etc. The mechanical methods include collection and destruction of infected plant parts and weeds as well as use of sticky traps. The biological methods include use of predators and chemical methods include use of fungicides & insecticides.
Irrigation and nutrients:
 Water stress and excess water is one of the most devastating factors as far as quality flower production is concerned. It has been observed that flowers produced under improper irrigation management are poor in quality and deficient in vase-life. For example excess salinity leads to fast senescence. Water deficit leads to bent necks & drooping of flower heads. In order to maintain the quality of produce, nutrient management also plays an important role. Deficiency or toxicity of nutrients adversely influences crop production.

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