Tuesday, 12 January 2016

The 5 Minute Fallow

The 5 Minute Fallow

Well after 2 years of trialling and testing, of calculating and studying our Cross Slot drill has finally arrived, imported all the way form New Zealand.  I say finally arrived, it actually arrived in July 2015 but shamefully I have neglected my blog, so here's an update on my latest thinking and plans.

The 5 minute fallow is the first place to start.  The picture above shows the drill planting a cover crop mix directly behind the combine.  Why are we doing this, I hear you ask?  The cover crop plants will stay in the ground after the oilseed rape has been harvested and before we plant wheat in the same field.  The job of the cover crop is to:

Cover Crop at 4 weeks old

  1. Intercept the sunlight during the period of maximum radiation and turn that sunlight into roots, shoots and leaves.  This plant material will have several benefits to the new zero tillage farming system we are adopting.  The roots will penetrate down in to the soil breaking up soil compaction, create drainage channels (when they die) and release sugars in the soil to feed the soil fungi and bacteria, which in turn feed earthworms.
  2. The leaves and stems of the plants will store nutrients that might otherwise leak or escape from the soil which could create pollution.  Things like sulphate and nitrate are very soluble in water  but non-mobile when part of a plant.
  3. Create soil armour.  August has always been the farms wettest month, with heavy thundery summer storms hammering down on the soil surface.  By having a protective shield on the surface, in the form of leaves, the rainfall is intercepted and can infiltrate at a faster rate, with reduced micro compaction on the surface.
  4. When the cover crop is destroyed the dead material will slowly turn into organic matter (OM) which can hold greater amounts of nutrients and water than mineral particles.  OM can potentially hold 10x more water than the mineral soil alone.  Few arable soils in the UK or around the world have OM levels greater than 5%, which is where it needs to be as a minimum.  The OM will help to feed the soil bacteria and fungi which in turn will help to feed our crops.
  5. Reduce weeds in the seed bank, as some of the seeds will be germinated when the cover crop is planted which will be destroyed with the cover crop.
After the cover crop comes the main crop in the case of the field below, wheat. This picture was taken at the end of October when the crop was about 4 weeks old and shows good even plant establishment with little sign of pest (slug) activity.  The crop, if anything, is a little too thick.  
Wheat Planted after Cover Crop
A cover crop is not a "fix all problems in the field from a bag, rather than a chemical container" but it does have a lot of advantages when it comes to improving the soil health and workability of the soil.  It will contribute to increasing OM levels and it will create drainage channels to improve water infiltration into the soil, key when reducing soil erosion and storing more water in the fields, and can help reduce flooding down-stream.  We use cover crops to reduce the exposure of our soils to the elements of wind, sun and water; all of which have massive long term benefits.  I will be back with a follow up blog on dealing with cover crops and getting the next crop established through increased levels of crop residue.