Nearly a quarter of the land area of Ireland is classified as heavy or poorly drained soil, and almost half of the agricultural land would benefit from reclamation and drainage, according to Teagasc experts at the recent open day on the Solohead Research Farm in Tipperary.
The objective of any form of land drainage is to lower the water-table. This promotes deeper rooting, which improves sward productivity. It also improves the load-bearing capacity of the soil and lessens the damage caused by grazing and machinery.
The potential of the land to be drained should be assessed first, to determine if the costs incurred will result in an economic return through additional yield and utilisation of the grass or other crops.
From a management point of view, it is better to drain the land nearer to the farmyard and work outwards.
However, it may be more beneficial to decide where to commence after the drainage potential has been established by site investigation.
The cost of drainage works will vary according to factors such as soil type, site access, extent of open drains, availability and cost of backfill stone, and experience with drainage works.
Where a shallow drainage system is considered, the price will depend largely on the collector drains required.
If an existing system of closely spaced piped drains is already in place at the appropriate depth, it may be possible to pull mole drains through this network — in which case mole drainage can be very cost effective.
Selection of a drainage system for a particular site should not be decided on the basis of cost.
An effective drainage system should be designed and costed and then a decision made as to whether or not to proceed.
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