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Flooding in Monmouthshire

Flooded field

Well what a week for weather. Gale force winds, so much rain and yet more flooding. After the summer we’ve had maybe it was too much to expect autumn would be kinder to us all. We’ve been lucky. We lost a fence panel to the wind but this can be replaced fairly easily come spring and the allotment is squelchy to say the least but compared to those who have had their homes inundated with flood water it’s nothing.

Much of the countryside around us is under water. The two main rivers, the Usk and the Wye have broken their banks and because we had such a wet summer the water table is already at full capacity. As a result, water is lying on saturated ground. It’s hard to tell what is river and what is a field in places. We popped into our local garden centre on Sunday to find the car park flooded and a makeshift walkway in place to access the shop.

Flooded garden centre

Garden centre car park

Eventually the water will subside and the ground will dry out but the consequences of so much rain go beyond the immediate problems of flooding. For farmers and gardeners the impact on the soil can be significant. Nutrients are held in the soil by electrical charges and are released into a film of liquid called soil water after a series of chemical reactions and exchanges. This soil water is held around soil particles and plant roots are able to absorb nutrients that are held in it. However, after lots of rain this film of water becomes so thick and heavy the soil cannot hold onto it and the nutrients are lost as water drains away. Heavy rain is to be expected over winter and in agriculture the ground is treated as being totally deficient in nitrogen by spring. Nitrogen, essential for leafy growth is a particularly soluble nutrient.

For farmers, soil testing and monitoring of nutrient levels has become an increasingly important part of their job, allowing them to increase yields but use expensive fertilisers only when and where they are needed. For gardeners it’s a very different story. Incorporating compost and manure is normally enough to ensure a fertile soil in our garden or on the allotment. The major nutrients, nitrogen, phosphorous and potassium are those that plants use the most and can be satisfactorily replaced with organic matter. Generally, it is uncommon for soils to lack the trace elements such as boron and manganese that are vital to plant growth but are only needed in tiny quantities. However, it is difficult to know how the unusually heavy rain this summer followed by the wet autumn will have affected nutrient levels in our soil. Certainly, tests of agricultural land are showing significantly lower levels of nutrients, although not all of this can be attributed to just the rain and is a result of changes in farming practices.

I’ve never felt the need to test my soil before other than doing a pH test. Listening to Gardener’s Question Time yesterday though I heard Christine Walkden say that nutrient leaching has been a significant problem this summer. Certainly some plants on the allotment have struggled this year and whilst I’m sure some of it was simply down to the lack of sunshine and warmth some of it may well have been down to a lack of the vital food they needed.

Sandy soils and those with little organic matter which already have good drainage are particularly prone to nutrient leaching but we’ve all had so much rain this year that it could well be a problem for a lot more of us. It is possible to buy kits which enable you to test your soil but these will only allow you to check the levels of the 3 major nutrients, nitrogen, phosphorous and potassium. These are the most essential though. They can be bought for between £20 to £30 from most of the major online gardening suppliers. Having never used one before I would love to hear if anyone else has had experience of using them, whether they were easy to use and were worth the trouble and cost.

It’s also possible to have your soil analysed by the RHS. A service available to both members and non-members, the charge being £25 and £30 respectively, it gives you the pH level, an idea of your soil structure, the level of organic matter in the soil and the levels of the major nutrients. It is certainly something I may consider.

Growing green manures is one way of protecting soil over winter. The leafy growth protects the surface of the soil from damage and the plant absorbs nutrients and holds on to these in the plant which are then released back into the soil. The problem for me this year was that I didn’t have any free ground to sow the manure into in September and October and my experience last year was that the seed struggled to put on enough growth to be useful if sown in mid October. Mulching with manure or compost will again protect the surface of the soil but there can be issues with manure regarding the leaching of nitrates into water courses. Although farmyard manure has much less nitrogen that is immediately available, unlike poultry manure, applying it to soil when there are no plants actively growing to take up soluble nitrogen means, particularly in periods of heavy rainfall, that it may leach from the soil. Although, just to confuse matters some growers believe nitrogen isn’t so readily leached from soils in the first place.

Nutrients are not only important for the plant, when we then eat that fruit and veg it is those nutrients that have allowed the plant to grow that we then absorb. It matters to all of us that our soils are healthy because in turn we too will be healthy. Perhaps the only way to find out the impact of all this rain is to test my soil.