Draining Waterlogged Soil
No vegetables or fruits will thrive in soil that remains wet for much of the year. Their roots will be starved of oxygen and it will be difficult to carry out cultivation work at the correct time. Signs of water-logging include persistent puddles after rain; algae and moss grow in and on the surface; and overwintered plants — such as sprouting broccoli — turning yellow and collapsing.
Sometimes, a badly drained garden can be improved in the course of digging; otherwise, it may be necessary to install underground drains before attempting to grow anything.
Improvement during digging is possible when the cause is a layer of impervious soil at about spade depth. This can occur naturally, due to what is termed an iron pan, or may be caused by continual ploughing or rotavating at a constant depth.
One or two trial holes will show whether such a layer exists. Double digging is the ideal remedy, but there is a simpler alternative:
Choose a time when the soil is fairly dry, and dig it over to spade depth in the usual way. As you complete each row of digging, work along the bottom of the trench with a fork, driving it in to its full depth and levering it back so that the soil is lifted and fractured. A pick-axe or mattock may be needed to break the hardest type of iron pan.
Do not attempt to turn the layer of subsoil beneath the pan. Just push the fork in, move it until the soil begins to give, then withdraw it again.
A cure is more difficult if water-logging occurs on heavy or low-lying land where there are insufficient outlets for the surplus water. The answer is to lay pipe drains, but this is worth attempting only when the trouble is really serious and if there is a ditch into which the pipes can empty.
Lacking a ditch, one solution is to construct a soakaway, although this will be of limited use during periods of prolonged and heavy rainfall — especially on a clay soil.
An alternative, for a very small area, is to make raised beds, for growing crops such as salads and tomatoes. Form the sides with bricks or stone blocks, and place a layer of rubble at the base.
If the problem is not extreme simply raise the overall level of the soil, using earth dug from drainage trenches at the side of the plot.
If you decide to lay pipe drains — also known as tiles — you can buy them from builders’ merchants or agricultural merchants. For garden use, choose pipes with an interior diameter of 2 or 3in (50 or 75 mm).
The best tool for digging deep, narrow trenches is a grafting spade with a narrow, slightly curved blade. It may be possible to borrow one from a builder; otherwise, use a narrow-bladed spade.
Lay the pipes with a slight fall towards the ditch or soakaway, with their ends about is in. (2 mm) apart so that water drains — also the surrounding soil. A drop of not less than 12 in in 30 yds (305 mm in 27 m) is sufficient, but in planning the system allow for about 12 in of soil or turf above the highest pipes.
If draining a large garden, for which a ditch outlet would be necessary, lay the pipes in a herringbone pattern, using 3in (75 mm) diameter tiles for the main drains leading to the ditch, and 2in (50 mm) tiles for the side drains. Space the side drains 30 ft (9 m) apart, and position them so that their inner ends coincide with joints in the main drain. Cover the connections with pieces of slate or tile, and pack turf around them.
Before placing pipes in a trench, lay 1in (25 mm) of gravel as a base. Place a further layer of gravel or small hardcore over them. Cover this with inverted turves or polythene sheeting.
THREE WAYS TO IMPROVE SOIL DRAINAGE
Make the bed 12-24in (30-60cm.) high. Place stones on the base, followed by gravel and a layer of turves, then fill with good soil.
Whether leading to a ditch or a soakaway, lay the earthenware pipes on a gravel base. Cover with more gravel, then a layer of turves or polythene sheeting.
Make the pit as large as possible — at least a cubic yard — and fill with stones or hardcore. Before placing soil on top, cover with polythene.