Why irrigate in the UK?

Posted on 25th February 2013 at 3:31pm

Drip Irrigation

With the UK's temperate climate, many people ask if it is worth irrigating. In this article we look at the benefits of irrigation.

Covered Areas and Restricted Root Zones
Where planting is under cover or experiences rain shadowing from tall buildings, irrigation is essential to keep the planting alive. If trees are planted in urban areas, with hard landscaping around the root area, irrigation will be needed to supply the trees water needs. Even medium sized trees require 100 litres per day in dry weather. Modern control systems can be programmed to take rainfall into account when scheduling outdoor irrigation zones while ignoring rainfall for covered or rain-shaddowed
 
Speeding up Establishment 

Where planting needs to mature quickly or is being used as screening, irrigation will greatly speed up the process. As the graph indicates, during the bulk of the UK growing season, 

plants experience a Water Deficit. This graph is for an 'average' English year, for a '1-in-5' dry year the deficit is even greater, as the rainfall levels are lower and the Evapo-transpiration (ET) levels are higher, widening the deficit between the two. As plants require water as part of their growth process unless this deficit is made up by irrigating, their growth will be reduced. As a rule of thumb irrigated landscape planting will establish approximately 50% faster than non-irrigated plants.
 
Reducing Plant Losses 
As landscape contractors generally have to provide a warranty with the plants, costs due to plant failure can be expensive, especially if there is an unusually dry spell. The cost of integrating an irrigation system into the planting scheme is often quite small compared to the cost of the planting. In addition, the irrigation can often be sold to the client as part of a 'value added' package.
The lack of water during the growing season not only limits the potential growth of the plants, it also increases the likelihood of diseased plants and specimens that do not survive. The cost of the labour in replacing the plant needs to be taken into account along with actual cost of the plant itself.
 
Reducing maintenance costs
During the first few weeks after Summer planting the plants will need to be watered regularly. Turf will quickly shrink back and die and planting into dry borders will struggle. An irrigation system can automate the task, saving many hours of time on-site.
 
Green Roof Systems
Soil is very heavy, so the deeper the substrate, the stronger the roof structure needs to be. As the strength of the roof increases, so does the carbon footprint of the building. By using a lightweight green roof structure, the load bearing structure of the building can be reduced, but the planting will quickly dry out. 

Using innovative control systems that only water after a prolonged dry spell, irrigation can ensure the plants thrive while ensuring precious water is not wasted. The use of irrigation also ensures that the sedum mats do not dry out and become detatched from the roof. 

 

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