Paying attention to your drainage and soil structure

2 September 2014

It’s surprising how quickly complacency can slip in – a month ago combines were charging on, cutting winter barley and OSR at record low moisture levels and we were all relaxed and anticipating an easy harvest, yet now we have wheat sprouting in the ear in the aftermath of Hurricane Bertha and a prolonged spell of broken weather. The further north, the worse it is.

On driving up to Aberdeenshire last weekend, the most striking sight for me were the fields with the blocks of un-harvested grain surrounded by the black marks where the combine had to back out before it got bogged down, or the tracks where the loaded trailers had been dragged out of the field.

Yet it wasn’t every field, so clearly the build-up of rainfall over the last three weeks has been enough to push the drainage / soil structure over the edge in particular fields only.

On the same trip I saw another sight I hadn’t seen for a while – two large scale drainage schemes going on. With some heavier ground still suffering post 2012, the message must be to pay closer attention to your drainage and soil structure. Not just the wet bits, but the whole farm.

With an early finish to harvest still on the cards, there will be more of an opportunity to rectify any drainage or soil structure issues before the next crop is drilled, or winter weather closes in. So rather than watching the Grand Prix on a Sunday afternoon, there are a couple of worthwhile things you might consider doing:

  • Take a spade and have a look at what’s happening below the surface in your stubble fields. Look below a tramline as well as across the field and if you find a compacted layer, note how deep it is. If you suspect damage below spade depth, take a note to investigate further with a digger.
  • Make a simple assessment of your soil health by counting the worms in your spadeful of soil. As a very rough guide:  <4 = poor;  4-8 = moderate;  >8 = good. From a drainage perspective the percolation rate (how quickly a soil drains) for a clay soil without worms is 0.2”/minute; with worms 0.8”/minute. So improving soil health / organic matter can also aid drainage.
  • Take note of any areas where the combine / grain trailer has made deeper tracks than normal. This may indicate a broken or partially blocked drain – relatively easy to rectify rather than driving around a wet hole next year. Check any old drainage plans you may have and see if there is any correlation.
  • This is also useful in reminding you of where the drain outfalls are so that they can be checked once vegetation dies back in the watercourse.

Soil Trench

Digging a trench to assess soil health

Avoid unnecessary sub-soiling by making sure you know what is causing the wet area, and if it is compaction, then what depth is it at?

As for me, I’ll be watching the Grand Prix!

Gavin Dick - Scotland

Gavin Dick - Scotland

AHDB Cereals & Oilseeds Manager (Scotland). Previously a business specialist with SAC, working to broaden farmers’ business management skills.