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Brown Rivers – Silt run-off

Graham Harvey

Archers agricultural adviser

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River in flood showing brown water

After that freak storm, the Am river – from which Ambridge gets its name –  has turned brown. This mirrors what is increasingly happening in rivers all over the UK, and indeed the world.

In the area where I live in Somerset, the local river is normally a sort of grey-green in colour. But whenever we get a spell of heavy rain, it runs reddy-brown. The colour change is the result of topsoil being washed from the fields high in the hills where the river rises.

The reason the soil is washing away is that the life has gone out of it. Together the billions of organisms that make up the living part of soils have been damaged by decades of treatment with chemical fertilisers and pesticides. As a result, large areas of farmland are becoming less and less able to carry on their normal functions of growing healthy crops and retaining moisture.

When the life goes out of soils, they collapse and erode away every time there’s a heavy rainstorm. It’s a process that’s going on across Britain, though the colour varies depending on the local soil type.



Degraded soils also pose a more immediate threat. They increase the risk of flooding. Because damaged soils hold less water than healthy ones, there’s a lot more run-off from the fields. And the silts washing into rivers decrease their flow and further increase the flood risk.

Many of today’s farming systems are based on chemistry. You measure the chemical elements taken out at harvest time, then replace them, or some of them, with chemical fertilisers.

But soil specialists will tell you that soils don’t work as chemical factories. Plants are nourished by the ceaseless activities of living organisms that enable them to take up the nutrients they need.

A growing number of farmers contend that modern farming systems damage these life forms, especially high-input crop growing of the sort that Charlie is pushing Adam to pursue on the Estate’s land.

At our recent long-term planning meeting, we heard from a farmer who is moving away from intensive monocultural arable production. He aims to put life back into the soil by returning to the mixed farming of his father’s younger days. Grass, clovers and deep-rooting herbs will improve the soil structure and ‘fix’ essential nitrogen from the air. And the manure from livestock will significantly reduce his reliance on chemical fertilisers.

He hopes for many benefits from this system. And one of them is that when the rain comes, his precious soil stays on his land and is not washed away to stain the rivers.

Graham Harvey is the agricultural advisor to The Archers

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