Other than lawns, watering the garden plants by means of drip irrigation is unquestionably more effective than by sprinklers and more efficient in terms of water management. Roughly speaking, drip irrigation, if installed and applied correctly, can save at least 20% of the water that is lost in run-off, especially where trees and shrubs are concerned. However, the great benefits of drip irrigation are often not attained by the home gardener, because three aspects are not addressed properly.
Working at the correct pressure
Drip irrigation should operate at as low a pressure as possible. In small, private gardens, a pressure of about 1.5 bars is appropriate. For this purpose, a pressure regulator ought to be installed at the system's head unit.
Very often, the drippers at the end of the line barely emit water. The reason is usually that the dripper line itself is too long and not because of insufficient pressure to begin with. A common mistake is to snake a line or two around the plants, instead of the correct method, which is to connect several shorter lines to a feeder or supply pipe. For most home garden situations, each dripper line should not be longer than about 15 meters, (45ft) and a lot less with micro-drippers.
Correct Spacing
It is best to use integrated lines, where the drippers are inserted at fixed intervals by the manufacturer. Distances of between 0.5m to 1m are appropriate for trees, shrubs and most ground covers, whereas an interval of 0.3 m (1ft) is usually necessary for flowers.
Likewise, the dripper lines should be parallel to each other and as evenly spaced as possible. However, the distance between the lines does not have to equal the distance between the drippers. In heavy soil for instance, where drops of water spread laterally, if the drippers are spaced at 0.5m then the lines can be laid 0.75m or even 1m from each other. Alternatively, in light, sandy soil, through which water tends to move vertically, the spacing between the rows ought to be closer.
The aim is to apply water at a rate at which it can be absorbed by the soil, while supplying an even cover of moisture for the plants' roots. For this reason, it is important to know the flow rate of the individual drippers. It is best to choose those with the lowest flow rate available (flow rate is the volume of water emitted per unit of time) especially in heavy, clay soils and on slopes. For flowers, where complete coverage is usually necessary, it is wise to use micro-drippers, where the flow rate of each unit is 1 liter per hour.
Care and maintenance
Blockages are the main problem associated with drippers. Firstly, a filter designed for drip irrigation should always be installed. Secondly, it is wise to flush the lines once or twice a year. This from my experience can extend the lifespan of the system to some 10-15 years, whereas failure to carry out this simple procedure is liable to result in blockages after 2-3 years. Ultimately, the drippers will block up from the mineral deposits that accumulate over time.
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