A drainage job working well 18 months later

Last week I returned to look at a drainage job that I featured 18 months ago on these pages. The work was carried out in August 2013, at the end of a dry summer. However, much of the low-lying 80 acres was waterlogged then, and could not be worked by a tractor. I watched the drainage job being carried out by Dessie Taaffe of Eagle Plant Hire.

Pictures one, two and three

The centre of this 20-acre field was wet. Dessie first cleaned out the ditches and then installed a central main drain through the wet area with 10 spurs, five each side. In picture two we see Dessie digging out for the main drain. The top soil was shallow, underneath layers of sandy, gritty material through which water could flow.

We can see the water flowing rapidly into the bottom of the trench. So great was this flow that Dessie decided to use a big, 9in main pipe (picture three). With soil caving in, he had to use the trapezoidal bucket. The pipes are rigid, twin-wall Corripipe from JFC. The trench is 40in deep and is covered with stone to within 20in of the top.

Pictures three, four and five

There was a remarkable difference when I visited last week, at the end of winter, admittedly a decent one. The ground was dry and very firm underfoot (picture four).

The land was ploughed and reseeded in autumn 2013, immediately after the drainage job. The ground is now able to support traffic (picture five). Here, we are looking along the line of the 9in main pipe, through what was the wettest part of this field. The new sward was grazed right down last autumn by cattle and sheep. It will thicken up over the next year or two with good fertilizer. The land is already significantly more productive now than it was in 2013.

Water is flowing 24/7 out of the main pipe (picture six), exactly what you want to see. It is taking water from the 10 spurs. These are 4in yellow coil pipe. Dessie Taaffe advises that after a drainage job like that carried out here, soil shouldn’t be overworked as this can leave surface water sitting on top, unable to travel down to the drainage stone and pipes. Soil that has been water-logged for a number of years has poor structure and is more at risk of compacting. Neither will it have had a chance to dry out after the drainage work. He recommends ploughing followed by tined harrow or a levelling harrow and minimal use of any power harrow. Water sat on top of some of this field in 2014 but this was rectified by pan busting to break up consolidated soil at the top.