Land drainage key for grass growth

Land drainage is seen as one of the most important components for achievement of Food Harvest 2020 goals.

This is according to Pat Tuohy of Teagasc Moorepark, who was speaking at day one of Positive Farmers annual conference.

“Almost half of the agricultural land in Ireland would benefit from reclamation and/or drainage; in some counties the percentage is higher,” he said.

Tuohy explained that high rainfall on soils with impeded drainage inhibits production and results in surface poaching damage and structural degradation by grazing livestock, as well as poor machinery traffic ability and low usage.

“Effective and sustainable artificial drainage can be used to increase the productivity on heavy, wet soils and improve grazing conditions, the length of the grazing season and overall utilisation.”

He continued: “A drainage scheme will only be worthwhile where it is well designed and implemented and the benefits generated more than covers the costs. A greater awareness is required regarding the underlying causes of drainage problems and how appropriate drainage systems can be designed and implemented.”

According to the Teagasc expert, drainage problems in Ireland are largely due to our complex geological and glacial history.

“The rate at which water moves through a soil varies enormously depending on the soil type and management. Open, gravelly, soils have a capacity for water flow that is hundreds of thousands of times that of a compacted heavy clay. In free dinning soils, the rate at which water flows downwards through the soil is always greater than that being supplied by rainfall. In poorly drained soils the rate of rainfall is often greater than the rate of infiltration at the soil surface due to: low hydraulic conductivity/permeability in the soil, or  layer of subsoil; high water table due to low lying position and poor/poorly maintained outfall; and upwards movement of water from seepage and springs.”

Tuohy explained that effective land drainage will have to solve one or more of these problems.

“The objective of any form of land drainage is to lower the water table providing better conditions for grass growth and utilisation.”

“A controlled water table promotes deeper rooting which improves sward productivity. It also improves load-bearing capacity of the soil and lessons the damage caused by grazing and machinery.”

In addition, he said when planning any drainage problem, the potential of the land to be drained should be assessed to determine if the costs incurred will result in an economic return through additional yield and use of the grass or other crops grown.

The new Teagasc manual on drainage and soil management is available at all Teagasc offices.

Day one of Positive Farmers’ annual conference in Clomel, Co Tipperary, achieved a record attendance of more than 475 people. Day two is currently under way, with a keynote address from Dutch co-op giant chairman, Piet Bower of Friesland Campina.