It might seem odd to talk about the problem of too much water when a large part of the country has been in drought for months but the two aren’t necessarily incompatible. Bad drainage is often a soil issue (and sometimes a topography issue), so even the driest, most drought-afflicted paddocks can still turn into bogs after rain.
If your land doesn’t drain well, you probably have a high water table and/or a heavy, clay-based soil. Clay particles are extremely small and very fine. There’s not much air between them, so there’s very little available space for water to penetrate. That’s why clay soils take a long time to drain. The up-side is that these soils retain moisture longer in dry months.
Five problems caused by bad drainage
- It reduces the area of workable land on your block and limits your options. Wet, boggy soil is unproductive.
- The soil becomes sour (acidic) and is vulnerable to compaction.
- It’s hard on farm machinery – getting a tractor bogged is no fun.
- The soil takes longer to heat up in spring because of its high water content, meaning your growing season is shortened.
- Your local council might take an interest and declare part of your property an official wetlands area. I’m serious – this happened to three of our neighbours!
How to fix bad drainage
The water table generally tends to rise in winter, so now is a good time to make plans on how to deal with your bog-prone areas.
- 1. Install a sub-surface drainage system
This is the fastest solution. DrainawayTM is a flexible, corrugated polythene pipe that’s available in two forms: slotted/punched or unslotted/unpunched. The slotted/punched pipe contains drainage holes that enable the groundwater to flow into the pipe so it can then be channelled into a stormwater drain or similar. The unslotted/unpunched pipe is used to transport water from one place to another.
DrainawayTM pipe is installed in a trench that’s both lined and back-filled with gravel. A heavy-duty version suitable for road drainage called Freeway Drain is also available through RX Plastics.
Bear in mind that there will be some nutrient loss when the water is drained off the property. If you use fertiliser, be careful about nitrate leaching. If you don’t use fertiliser but you’re still concerned about nutrient loss, consider creating a small pond or reed system and diverting the water to that.
- 2. Create swales or diversion ditches
Swales and diversion ditches capture water runoff and store it so it can slowly percolate into the ground. Swales are a popular solution in permaculture practice. To be effective, they must be dug on contour. They’re easy to construct but if you’re considering this option, research thoroughly or consult an expert before hiring a digger. Swales don’t drain well on heavy clays and they can create frost pockets.
- 3. Plant trees
For generations, Kiwi farmers have been planting willows and poplars in boggy areas to drain them. These trees can remove large amounts of water from the ground, with the added bonus of providing high-quality, nutritious fodder for livestock. They coppice well, which increases their lifespan considerably, but this means they need regular maintenance. These trees may not be suitable for smaller blocks, and willow roots in particular will travel very long distances in search of water. Inquire at a specialist tree nursery about the most suitable varieties to plant. If there’s any chance they’ll find your septic tank, consider other options.
About the Author
Niki Morrell is a writer who is learning how to farm 25 hectares of marginal land and beech forest in the Nelson Lakes area. With no background or prior experience in farming, she spends much of her time alternating between elation and despair. She says, however, that she wouldn’t have it any other way.Follow on Google Plus More Content by Niki Morrell