Greenhouse Watering and Feeding Equipment
Watering and feeding equipment
The application of water and soluble nutrients is an essential part of greenhouse gardening. Watering methods may be as simple as a watering can filled directly from a tap or barrel or tank topped up by a hose, and liquid fertilizer used for each watering can application. Alternatively liquid fertilizer can be dissolved in barrels or tanks, but great care should be taken to measure both water and liquid fertilizer accurately.
Few modern commercial holdings are without some form of automatic or semi-automatic watering device, with the complementary use of dilutors for liquid fertilizer application. Amateur gardeners are fast catching on to the fact that there is great scope here, not only for reducing labour, but for ensuring greater accuracy in the realm of water and liquid fertilizer application, using dilutors at hose ends.
A greenhouse should have a good tap supplying water at a fair volume and pressure. Screwed taps or ‘plug’ types are preferable to plain types as they allow hose couplings with no leaks. Meters for fitting to taps are now available.
These are available in tough plastic ranging from 2.25 litres (½ gal) capacity upwards, the most popular being the 4.5 litres (1gal) size, both for weight and for ease of measuring up liquid fertilizers. Enamelled metal cans are still very popular, although more expensive, and range from 1.7-9 litres (3 — 16pt). Diminutive copper watering cans are useful for house plants and are generally 0.5-1.1 litre (1 — 2pt) capacity. A selection ofis available to give fine or coarse droplets of water.
Containers for water
Old sinks or wooden barrels are frequently used as reservoirs for water, though modern plastic water baths holding from 112180 litres (25-40gal) are available and are much more hygienic as they can readily be washed out. This is essential for all forms of water storage, as algae and scum can quickly grow on still water, a further problem being contamination with bacterial and fungal diseases. It helps if containers are shaded.
These provide large droplets of water from revolving nozzles spaced approximately 2.4-4.5m (8-15ft) apart. They arc installed at a height of 1.8-2.4m (6-8ft) according to headroom available, and if sufficient volume and pressure of water is available, will dispense droplets over an area within a distance of approximately 6m(20ft) at a water pressure of between 1.3-2.6bar (20-40psi). Their main role is for the damping down of crops such as, to shake the plants and assist with pollination, and they have therefore little general application. They are available generally in alloy with quick release couplings.
These can take several different forms and are available in both alloy or plastic, the latter tending to sag a little unless adequately supported. They can be used either at high or low level and are available with nozzle sprays spaced approximately 1.5 to 2.25m (5ft to 7ft 6in) apart with different sized jets for operating at different pressures. Typical output of 2.3mm ( 3 in) jets ranges from 81 litres (18gal) per hour at 0.6bar (10psi) up to 240 litres (53gal) per hour at 2.6bar (40psi) 7 /64 pressure. For larger jets of 5.5mm (674m) the outputs are nearly doubled and range from 136 litres (30gal) per hour at 0.6bar (10psi) to 363 litres (80gal) per hour at 2.6bar (40psi). The specification for spraylines varies according to manufacturer, as do the trajectories of the nozzles or jets. Fine atomization is generally achieved at good working pressure, which saturates the whole growing area.
The details given apply merely to commercial equipment, which of course can be utilized for large amateur. For small amateur greenhouses spraylines of various types are available with much closer nozzle sprays, generally 1m (3-4ft), for operating a 3m (10ft) spray-line from a 1.5cm (in) hosepipe, and usually require a water pressure of 2.4bar (35psi). The output per hour of these units will obviously vary greatly according to the specification, and it is a matter which must be taken up with the supplier.
Control of spraylines can be effected either on a time basis with a solenoid valve through a sequence controller on a large scale or more simply with a hand-operated tap on a small scale. ‘Automatic’ waterers are also available which operate either on the saturation of a moisture sensitive pad or by a selenium light cell or other methods similar to those used to control mist irrigation units. The main drawback of spray-lines lies in their inability tointo containers protected by foliage. Spray-lines are therefore more useful for crops such as , used au a high level until the plants reach 1.5m (5ft) then at low level generally at 30cm (12in) on wire supports, and covering a smaller area. Lettuce crops and other bordergrown plants are successfully watered with spraylines.
Damping down is effectively carried out with spraylines, increasing the humidity and reducing water needs, which is valuable for the gardener absent during the day, particularly when the spraylines are linked to an automatic device. A fair quantity of water can reach the pots in many instances. Liquid fertilizers can also be applied through spraylines in a form which makes them readily acceptable to the plants, either through their leaves or in the.
These take several forms, all having in common the precise placement of droplets of water in a pot, container or growing border. The ability of water deposited in droplet form at a specific point to move through the growing medium varies within the type of medium. It has been found in certain free-draining light soils that trickle systems do not adequately water a sufficiently wide zone, although this can be overcome by moving the position of the nozzle at regular intervals. There are two basic forms: those where plastic nozzles are used in a rubber hose, or ‘spaghetti’ systems where capillary tubes lead out to each plant and are held in position by a peg. Trickle systems can be used for either border-grown, container-grown, grow bags or bench-grown plants and can be either manually operated or by a timing device operating a solenoid valve, or by a light cell.
Low-level watering systems Perforated ‘lay-flat’ polythene tubing of 5cm (2in) width throws out fine jets of water on expansion with a sufficient volume of water and is a useful system for border-grown plants. It is not so suitable for container-grown plants. Round PVC tubing with small holes operates in a similar way, but is not usually so efficient as a trickle system. More recently bi-wall tubing has been introduced to even up emission of water from small holes. Overhead gantry watering systems are now used commercially.
These are still indispensable for watering on a small scale, but care must be taken to avoid damage to soil structure by allowing an open-ended hose to splash on to the soil with force. Soil thus splashed on to tomato fruit is a frequent cause of fruit rotting. A rose or other attachment on the end of the hose can do much to avoid indiscriminate water dispersal, even a paraquat weedkiller dispenser being useful (but used only for water application) especially forand other border-grown crops. Damping down is frequently practised with a hose-pipe by pinching in the end, or by using a fine rose. Trigger lances are now popular.
While, as stated earlier, liquid fertilizers can be mixed as required in small quantities or prepared in bulk, a much more satisfactory arrangement is to use a dilutor into which the stock or concentrated solution of fertilizer is placed, the dilutor then being set at the correct dilution rate and placed in the supply line for spraylines or irrigation nozzles. Bottle dilutors are now used almost entirely on the displacement principle, although other systems work on a capillary tube system. Problems arise where water pressures are erratic, as this can both damage the dilutor and alter the dilution rate. In addition, although now available, it is not generally permitted to connect dilutors direct to a mains supply. Proprietary liquid fertilizers are usually colour dyed so that a quick visual check on dilution is possible, although on a large scale the concentration check of the liquid fertilizer should be regularly carried out with a salt meter. Self-formulated feeds should also be colour dyed for visual checking. Note that a bottle of correctly diluted liquid feed should be available for colour comparison purposes. The quantities of water and soluble feed required by various plants is dealt with under cultural notes referring to each crop.
Assessing the water requirement of crops
In addition to controlling the application of water by solenoid valves, sequence controllers and other apparatus, various methods are used actually to determine the needs of the crop. The simplest of these is a tensiometer, a device which consists largely of a ceramic pot connected to a vacuum gauge, graduated in centimetres or inches of mercury.
This instrument indicates the suction necessary to extract water and can be related to the water requirement of the crop. The evaporimeter consists of sand in a thistle funnel connected to a graduated tube, so that the evaporation of water can be calculated and related to crop needs. More recently simple, sensitive, tipped water meters, which state whether soil in pots or borders is ‘wet’, ‘medium’ or ‘dry’, have been available.
Solarimeters are installed regionally at research stations and record the solar radiation, so that water requirements can be issued to the commercial horticulture industry.