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How to assess your soil
"Soil is a farmer’s biggest asset," says our deputy director, David Michie. "Every farm has it, and it has the biggest influence on production and yield. But you can’t figure out how to improve it until you know what you’ve got.”
Picture: Expert Liz Stockdale investigates what is growing on top, then looks for clues inside the divet, such as smell, colour and root depth.
David’s tips on how to assess your soil:
1/ Dig a hole
Dig a hole in a field or part of a field that’s under-performing, and bring out a spadeful of soil. Pull it apart with your hands, looking out for:
Compaction. If the soil is very solid, like concrete, and breaks into big bits rather than crumbling, it doesn’t have enough air in it. This can be due to machinery, poaching, or too much rain weighing it down. Soil is a living thing, it needs to breathe. If soil is compacted you could consider using a sward lifter (flat lifter) or aerator.
Smell. Soil should smell earthy. If it smells eggy, or rank, it’s another indication that it doesn’t have enough air in it.
Colour. If it looks grey, with red or orange mottling, it’s another sign of poor drainage.
2/ Know your alphabet: pH, P and K
It’s best to send a sample of your soil to a lab to check its chemistry. If it’s much too acidic (below pH6) then you’ll need to apply some lime. Grass and crops grown in very acidic soils won’t yield well, no matter how much fertiliser you throw at them. You’re also looking for moderate levels of phosphate (P) and potassium (K).
3/ Count the worms
Biology is important – you should have as much microbial activity in the first six inches of soil as livestock supported above it. There should be around 25 earthworms per cubic foot and you shouldn’t have to dig too deep to find them. There should be a variety of different kinds, shapes and sizes, of a deep, healthy colour, and they should be actively wriggling about. No worms could mean compacted soils, or too low a pH.