Irrigation Systems In A Greenhouse:

In this article you will learn about irrigation systems in a greenhouse or different types of watering systems for greenhouse cultivation along with their advantages and disadvantages.

Table of Contents of Irrigation Sytems in a Greenhouse

  • Introduction to Irrigation System
  • Types of Irrigation Systems in a Greenhouse
    1. Hand Watering
    2. Overhead Sprinkler
    3. Boom Watering
    4. Drip Irrigation
    5. Tube Watering
    6. Ebb and Flow Watering
    7. Perimeter Watering

IRRIGATION SYSTEMS IN A GREENHOUSE

In irrigation systems in a greenhouse, Greenhouse crops are irrigated by means of applying water to the media surface through drip tubes or tapes, by hand using a hose, overhead sprinklers and booms or by applying water through the bottom of the container through sub-irrigation or by using a combination of these delivery systems.

Overhead sprinklers and hand watering have a tendency to “waste” water and also wet the foliage, which increases the potential for diseases and injury.

Drip and sub-irrigation systems are the most efficient and provide greater control over the amount of water applied.

Rules of Watering:-

The following are the important rules of the application of irrigation.

  • Rule 1:- Use a well-drained substrate with good structure if the root substrate is not well-drained and aerated, proper watering can not be achieved. Hence substrates with ample moisture retention along with good aeration are indispensable for the proper growth of the plants. The desired combination of coarse texture and highly stable structure can be obtained from the formulated substrates and not from field soil alone.
  • Rule 2:- Water thoroughly each time partial watering of the substrates should be avoided; the supplied water should flow from the bottom in case of containers, and the root zone is wetted thoroughly in case of beds. As a rule, 10 to 15% excess of water is supplied. In general, the water requirement for soil-based substrates is at a rate of 20 l/m 2 of bench, 0.3 to 0.35 liters per 16.5 cm diameter pot.
  • Rule 3:- Water just before initial moisture stress occurs since over watering reduces the aeration and root development, water should be applied just before the plant enters the early symptoms of water stress. The foliar symptoms, such as texture, color, and turbidity can be used to determine the moisture stress, but vary with crops. For crops that do not show any symptoms, color, feel and weight of the substrates are used for wet there is a reduced potential for diseases and injurious assessment.

Types of Irrigation Systems In a Greenhouse

  1. Hand watering:- 
  • The most traditional method of irrigation systems in a greenhouse is hand watering and in present days is uneconomical.
  • Growers can afford hand watering only where a crop is still at a high density, such as in seed beds, or when they are watered at a few selected pots or areas that have dried sooner than others.
  • In all cases, the labor saved will pay for the automatic system in less than one year. It soon will become apparent that this cost is too high.
  • In addition to this deterrent to hand watering, there are 2 great risks of applying too little water or of waiting too long between watering.
  • Hand watering requires considerable time and is very boring. It is usually performed by inexperienced employees, who may be tempted to speed up the job or put it off to another time.
  • Automatic watering is rapid and easy and is performed by the grower itself.
  • Where hand watering is practiced, a water breaker should be used at the end of the hose. Such a device breaks the force of the water, permitting a higher flow rate without washing the root substrate out of the bench or pot.
  • It also lessens the risk of disrupting the structure of the substrate surface.

Advantages Of Hand Watering System:-

  • The simplest and most common irrigation systems in a greenhouse is a garden hose or a portable sprinkler.
  • The advantage of hand watering is that you can easily avoid overwatering.
  • Uses a nozzle to control the flow.
  • When water stops being absorbed into the ground, move to another location.

Disadvantages of Hand Watering System:-

  • It is a time consuming process.
  • If someone is inexperienced there is good chance plants will either over or underwater.
  • Hand watering allows each person to water there area to their liking.
  1. Overhead sprinkler irrigation system:-
  • While the foliage on the majority of crops should be kept dry for disease control purposes, a few crops do tolerate wet foliage.
  • These few crops can most easily and cheaply be irrigated from overhead. Bedding plants, azalea liners, and some green plants are crops commonly watered from overhead.
  • A pipe is installed along the middle of a bed. Riser pipes are installed periodically to a height well above the final height of the crop.
  • A total height of 0.6 m is sufficient for bedding plant flats and 1.8 m for fresh flowers.
  • A nozzle is installed at the top of each riser. Nozzles vary from those that throw a 360° pattern continuously to types that rotate around a 360° circle.
  • Trays are sometimes placed under pots to collect water that would otherwise fall on the ground between pots and wasted.
  • Each tray is square and meets the adjacent tray. In this way nearly all water is intercepted.
  • Each tray has a depression to accommodate the pot and is then angled upward from the pot toward the tray perimeter.
  • The trays also have drain holes, which allow drainage of excess water and store a certain quantity, which is subsequently absorbed by the substrate.

Advantages of overhead sprinkler irrigation system:-

  • It is affordable and completely easy to set up. You will not need to spend much on a labor cost for setting it up.
  • There is no requirement of using many areas of your field for setting up the sprinkler irrigation.
  • The interference with cultivation for setting up the sprinkler irrigation is very less.
  • The water distribution will always be equal.

Disadvantages of overhead sprinkler irrigation system:-

  • The cost investment cost required for purchasing the equipment of the sprinkler irrigation system is high.
  • Using the sprinkler irrigation for supplying saline water can result in problems to arise.
  • For spraying water droplets evenly there is a requirement of constant water supply.
  • There is a requirement of continuous power supply for operating the sprinkler irrigation system.
  1. Boom Watering Irrigation System:-
  • Boom watering can function either as open or a closed system, and is used often for the production of seedlings grown in plug trays.
  • Plug trays are plastic trays that have width and length dimensions of approximately 30 × 61 cm, a depth of 13 to 38 mm, and contain about 100 3 to 800 cells.
  • Each seedling was grown in its own individual cell. Precision of watering is extremely important during the 2 to 8 week production time of plug seedlings.
  • A boom watering type of irrigation systems in a greenhouse system generally consists of a water pipe boom that extends from one side of a greenhouse bay to the other.
  • The pipe is fitted with nozzles that can spray either water or fertilizer solution down onto the crop.
  • The boom is attached at its center point to a carriage that rides along rails, often suspended above the center walk of the greenhouse bay.
  • In this way, the boom can pass from one end of the bay to the other. The boom is propelled by an electric motor.
  • The quantity of water delivered per unit area of plants is adjusted by the speed at which the boom travels.

Advantages of boom watering system:-

  • Less water is needed because the system can be operated to provide the optimum amount of water for the crop.
  • Less aisle space is needed for watering.
  • Labor is reduced as irrigation can be done while doing other chores.
  • Because of the large number of options, careful selection of a boom system is required.
  • Factors affecting your selection include type and style of greenhouses, cropping system, water quantity and quality and the amount of automation you desire.

Disadvantages of boom watering system:-

  • Provokes waterlogging and depletion of water sources.
  • Leads to water table lowering.
  • Contributes to soil infertility.
  • Contamination of local groundwater basins and stream flows.
  • Spreads water-born diseases.

4. Drip Irrigation:- 

  • Drip irrigation, is another type of irrigation system in a greenhouse, often referred to as trickle irrigation, consists of laying plastic tubes of small diameter on the surface or subsurface of the field or greenhouse beside or beneath the plants.
  • Water is delivered to the plants at frequent intervals through small holes or emitters located along the tube.
  • Drip irrigation systems are commonly used in combination with protected agriculture, as an integral and essential part of the comprehensive design.
  • When using plastic mulches, row covers, or greenhouses, drip irrigation is the only means of applying uniform water and fertilizer to the plants.
  • Drip irrigation provides maximum control over environment variability; it assures optimum production with minimal use of water, while conserving soil and fertilizer nutrients; and controls water, fertilizer, labor and machinery costs. Drip irrigation is the best means of water conservation.
  • In general, the application efficiency is 90 to 95%, compared with a sprinkler at 70% and furrow irrigation at 60 to 80%, depending on soil type, level of field and how water is applied to the furrows.
  • Drip irrigation is not only recommended for protected agriculture but also for open field crop production, especially in arid and semi-arid regions of the world.
  • One of the disadvantages of drip irrigation is the initial cost of equipment per acre, which may be higher than other systems of irrigation.
  • However, these costs must be evaluated through comparison with the expense of land preparation and maintenance often required by surface irrigation.
  • Basic equipment for irrigation consists of a pump, a mainline, delivery pipes, manifold, and drip tape laterals or emitters.
  • The head, between the pump and the pipeline network, usually consists of control valves, couplings, filters, time clocks, fertilizer injectors, pressure regulators, flow meters, and gauges.
  • Since the water passes through very small outlets in emitters, it is an absolute necessity that it should be screened, filtered, or both, before it is distributed in the pipe system.
  • The initial field positioning and layout of a drip system is influenced by the topography of the land and the cost of various system configurations.

Advantages of drip irrigation:-

  • Field leveling is not necessary.
  • Fields with irregular shapes are easily accommodated.
  • Recycled non-potable water can be safely used.
  • Moisture within the root zone can be maintained at field capacity.
  • Soil type plays a less important role in the frequency of irrigation.
  • Soil erosion is lessened.
  • Weed growth is lessened.
  • Water distribution is highly uniform, controlled by the output of each nozzle.
  • Labor cost is less than other irrigation methods.

Disadvantages of drip irrigation:-

  • Initial costs can be more than overhead systems.
  • The sun can affect the tubes used for drip irrigation, shortening their lifespan.
  • The risks of degrading plastic affecting the soil content and food crops.
  • Which would cause the plastic to retain flexibility have been released into the surrounding environment.
  • If the water is not properly filtered and the equipment not properly maintained.
  • For subsurface drip the irrigator cannot see the water that is applied.

5. Tube Watering Irrigation System:-

  • This type of irrigation systems in a greenhouse system is mostly used for watering the pots.water is carried to each pot by the polythene micro tube these microtubes are available in different inner diameter varying from 0.9, 1.1, 1.3 and 1.5mm micro tube will be able to handle 600,900,700and 400 pots respectively.
  • These microtubes should be provided with a weight at the end of its so that speed of the water can be broken otherwise there is a danger that pipe being thrown out of the pot and will dig a small pit medium.
  1. Ebb And Flow Irrigation system:-
  • Ebb and flow system is a sub-irrigation system for potted and bedding plant pots or flats are grown in level, water, tight bench.fertizer is applied at each watering.
  • The nutrient solution is tested, altered as required and recycled for a month it is not a Nutri-culture system in that conventional root media and containers are used.it is no so popular as it needs to meet antipollution standards.

Advantages of ebb and flow system:-

  • Fertilizer effluent can nearly eliminate since the ebb and flow system is closed.
  • Less water and fertilizer are used.
  • It is easy to change from one pot size to another between crops.
  • In a tube watering system it would be necessary to change the density of tubes.

Disadvantages of ebb and flow system:-

  • It is a very expensive method system.
  • The system has a high relative humidity that can buildup in the canopy of plants this situation can lead to condensation and ultimately to foliar diseases.
  • Humidity rises because air is unable to circulate through the floor of the bench.
  1. Perimeter Watering System:-
  • Perimeter irrigation system in a greenhouse can be used for crop production in benches or beds. A typical system consists of a plastic pipe around the perimeter of a bench with nozzles that spray water over the substrate surface below the foliage.
  • Either polythene or PVC pipe can be used. While PVC pipe has the advantage of being very a stationery, polythene pipe tends to roll if it is not anchored firmly to the side of the bench.
  • This causes nozzles to rise or fall from proper orientation to the substrate surface.
  • Nozzles are made of nylon or a hard plastic and are available to put out a spray are of 180°, 90° or 45°.
  • Regardless of the types of nozzles used, they are staggered across the benches so that each nozzle projects out between two other nozzles on the opposite side.
  • Perimeter watering systems with 180° nozzles require one water valve for benches up to 30.5 m in length.

8. Fertigation System:-

  • In a fertigation system of irrigation system in a greenhouse, an automatic mixing and dispensing unit is installed which consists of three systems pump and a supplying device.
  • The fertilizers are dissolved separately in tanks and are mixed in a given ratio and supplied to the plants through drippers.
  • Fertilizer dosage has to be dependent on growing media.
  • Soilless mixes have lower nutrient holding capacity and therefore require more frequent fertilizer application.
  • Essential elements are at their maximum availability in the pH range of 5.5 to 6.5.
  • In general microelements are more readily available at lower pH ranges, while macro elements are more readily available at pH 6 and higher.

Advantages of fertigation system:-

  • Improves efficiency in fertilizer use.
  • High nutrient availability due to the maintenance of soil moisture near field capacity under drip irrigation.
  • Fertilizers could be applied as frequently as possible and at those stages of crop growth when the demand is maximum.
  • Higher water use efficiency and 30 to 40 percent economy in the use of irrigation.

Disadvantages of fertigation system:-

  • Uneven nutrient distribution occurs when the irrigation system is faulty. It leads to overfertilization or leaching of nutrients when excess water is applied to crops.
  • Chemical reactions of fertilizer with calcium and magnesium, bicarbonates in water, which can lead to chemical clogging.
  • Suitable for readily soluble or liquid fertilizers. Phosphatic fertilizer and some micro-nutrients may precipitate in micro-irrigation system.
  • Corrosion-resistant fertigation equipments are needed.
  • Potential chemical backflow into the water supply sources.