The erratic weather conditions we continue to face in the UK means waterlogged allotments have become a common sight.
Waterlogging isn’t just a frustrating experience when there are jobs to get done, it’s a potential death sentence for your crops and the soil in which they grow.
In the winter of 2015, I’d turned a corner in the development of our allotment garden. After six months of ineffective, disorganised cultivation of the overgrown patch, I’d set out a plan of action and progress was only a spade turn away.
Then it started to rain.
The rain continued for weeks. Every morning I looked out of the window and wondered if it would ever stop. There were many jobs to do on the allotment in preparation for the busy spring.
When the rain finally stopped, I raced to the plot and was horrified. The allotment was flooded. This wasn’t a garden, it was a pond.
What is waterlogging?
Waterlogging occurs when the soil becomes saturated. On our plot, the pooled water was an obvious sign but water doesn’t have to appear on the surface of the soil for there to be a potential problem with waterlogging.
When allotments are waterlogged, air pockets in the soil fill with water and the roots of the plants are unable to get oxygen. Carbon dioxide and ethylene also build-up as the plants are unable to respire in the saturated soil.
Most of the time waterlogging doesn’t last long enough for plants to die. However, if allotments remain waterlogged for a significant period of time, the lack of oxygen in the root area will cause the root tissue to decompose.
How to solve the problem of waterlogging
Waterlogging can be prevented by achieving two objectives: Aerating the soil and enabling drainage of excess water.
Consider your soil
The soil on our allotment is heavy clay. It can be very fertile for many crops, however, it needs to be managed well for this to become as the farmers say – Strong land.
Clay soil can become a sticky mass. It can become almost impossible to cultivate, and when it dries out it becomes as hard as cement. In wet conditions, the clay soil on your allotment can exacerbate the problem of waterlogging.
Clay soil needs to be improved for it to flocculate – this means the microscopic particles which make up the clay gather together in larger particles. To improve clay you have to get as much organic matter, such as manure and compost, into the soil. The result will be a soil that is more easily worked, drains better, allows air to get down into it and allows the roots of plants to penetrate it more easily.
Land drains are an ancient but effective method for managing waterlogged ground. Creating drains can be hard work but you only need to do it once.
If your allotment slopes, you can drain the plot by digging a ditch at the top of the plot to cut-off the water running on to it and digging another ditch at the bottom of the plot to drain away excess water from the plot itself.
On most allotments, a ditch at the bottom of the slope should be enough. Traditionally, the ditch is filled with a few inches of gravel and a perforated plastic pipe is then laid along the ditch to guide the water away from the plot. More gravel is added to the ditch and then it’s backfilled with topsoil.
Our allotment doesn’t slope and so I’ve improved drainage using ditches to effectively lower the water table around the beds. This was achieved by digging out a network of paths and backfilling the paths with wood chips. The soil from the paths was then used to raise the level of the beds. It’s been hard work but it works.
Raised beds are an intensive strategy for the management of waterlogged allotments but are very effective.
As well as the prevention of excess water, raised beds are an advantage as they cut down on regular maintenance. A raised bed system can look attractive and the soil can be tailored in each bed for particular crops.
Most of the raised beds constructed on our allotment are 4ft by 10ft which is an adequate size to grow most crops. I’ve also constructed beds that are 10ft by 10ft which provides some extra space for crops such as potatoes and squash. This system of raised beds will continue into the other half of the allotment still to be cultivated .
Waterlogging is a serious problem faced by many allotment holders across the country, especially during the winter months. It can be daunting to see your allotment looking like a pond but don’t give up. Waterlogging can be resolved if you put in the work and utilise the methods described above.
Alys Fowler’s excellent article on growing a wide diversity of fruit and vegetables as the best way to mitigate changeable weather, particularly by growing perennials. Available from the Guardian: Alys Fowler: how to cope with changeable weather.
The RHS: Waterlogging and flooding
The November issue of Grow your Own Magazine has advice for waterlogged veg beds.