Crop Management for Flood Defence

Having seen some of the worst flooding in recent memory towards the end of 2019, there were calls for various measures to be implemented to stop a repeat. One argument was that land managers and farmers weren’t planting the right crops in the right areas, which was having a detrimental effect on soil management and increasing rainwater run-off.

Here, we take a look at the importance of effective soil management and how this can benefit both the environment and flood defence.


Soil management

To get the most from soil you must actively manage it. This means anticipating problems and adapting to prevent damage and enhance soil fertility. Well managed soil is both more fertile and easier to work with. If soil is well looked after it will drain well, meaning it is more resilient against compaction which in turn will act as a first defence against flooding.

Good soil management goes hand in hand with good crop management and rotation – it is important to position crops in the right area. Managing crop rotation correctly and growing crops sensibly in the right field will naturally reduce run off and help soil retain nutrients.

For example, it wouldn’t be sensible to plant potatoes or sugar beet in a field that slopes directly into a river as they have a later harvest and it minimises the chance of getting another crop in afterwards. If this were the case the field would remain empty through the winter and be exposed to the elements. This would result in run off, meaning the soil’s nutrients would find the water course and be lost. If there is no water course it will run down roads and block drains – once drains are blocked it results in further flooding as other water cannot drain.

Where there are sloped fields it is very important to plant a follow crop. To achieve this, an early variety should be chosen, and effort should be made to get the crop off to an early a start as possible. This is particularly relevant to maize.


Catch and Cover Crops

There is an extensive list of crops that can be used for effective soil management and, it is important to remember that growing any crop is going to be better than bare soil!

However, there are some crops that we particularly recommend, such as radishes, fodder radish and Phacelia. These are a good option because they have a low seed rate, are relatively cheap and will pull up nutrients and store them in their green, leafy canopy. Another advantage is that they are quick to get going and easy to establish. Any crop with these qualities is ideal when looking to manage soil and prevent flood water run-off. Additionally, if you choose the correct variety of fodder radish – like Radical – it won’t cause or harbour club root.

In terms of cover crops, keeping it simple and using crops like over wintering or green manuring is recommended. Make sure to choose which to plant depending how late it is into the autumn it is getting.

The advantage of getting green cover in the ground aligns with the theory of the soil not seeing the sun – something that is indeed important. When there is green cover over the soil, rainwater will hit the canopy and penetrate the soil at a more measured rate; allowing water to travel down to the roots and hold everything together. Without this cover, rainwater will fall directly onto the soil and gather momentum whilst running down the field.

If this happens, run off will inevitably take the topsoil with it. And, as farmers and landowners often suggest, topsoil is one of the most valuable things on the farm – if topsoil is not performing, yield will undoubtably be affected. It can take thousands of years for good topsoil to build so it is essential to look after well.

Although the primary bulk of nutrients are in the topsoil, it is equally important to have aerobic soil that contains a good level of oxygen – as opposed to it being anaerobic when the use of a subsoiler is needed. The majority of crops mentioned will help substantially with aerating the soil, as the roots will open it up and allow worms to move between the crops and form natural drainage.

Charles Darwin said “the most important creature on Earth is the earthworm” and he was right! When the crop is desiccated after the winter, the worms do a lot of work to help incorporate and transfuse the dying cover crop down through the soil profiles; something which assists the soil substantially.


An abundance of benefits

So, although soil management and crop rotation aren’t going to tackle to issue of flood prevention on its own, it is a sensible practise and can be highly effective in preventing run off. It also prevents sediment going into rivers and is a useful way to retain valuable nutrients in topsoil.

Good soil management also means that the ground can be harvested for years to come, without the need for excessive fertiliser usage. There is a limited stock of bagged fertiliser as it is made by mining nitrates and phosphates and, much like fossil fuels, there is a limited stock; demonstrating that fertiliser won’t always be available.

Therefore, holding onto the nutrients in topsoil is better for our environment and better for farmers financially, as there is no need to purchase fertiliser. Cover crops will help with this as part of a complete farming system.

If any of the previous points are of particular interest, it may be worth looking into Catchment Sensitive Farming or speaking to your local water companies – as funding in some areas of the country has been made available to help with these projects specifically.