Saturday, 6 February 2016

Big cover-up

There is increasing interest in the role of cover crops in improving various aspects of soil function such as soil structure for growing crops and soil erosion reduction.  Cover crops such as various brassicas, oats, rye, vetch, Phacelia and buckwheat are sown soon after harvest and destroyed prior to drilling the following spring crop.   Such over-winter green cover is eligible for funding under Countryside Stewardship or Ecological Focus Area (EFA) requirements so could potentially cover a large area nationally.

Through root growth, return of plant material to the soil, and associated soil biological activity, cover crops have the potential to increase soil orgainc matter, improve crop rooting capacity and nutrient uptake, increase infiltration and reduce soil erosion and asociated impacts on watercourses.  But perhaps this is all too good to be true!  We certainly need to understand more about the benefits on different soil types, and importantly, also the limitations and costs involved.

We are experiemntally testing both simple and complex mixtures of cover cops at Loddington
As part of our research with the Sustainable Intensification research Platform (SIP), we have set up experimental plots of cover crops comprising a simple EFA mix, a more complex EFA mix, and a fertility building mix, as well as a control (bare stubble) plot, replicated across three fields.  Working with our SIP partners, NIAB TAG, our Soil Scientist, Dr Felicity Crotty, is gathering data on a range of soil biological, physical and chemical properties across all the plots.  Very early results from the autumn suggest little difference in soil biology across the treatments, but slightly higher soil compaction in the plots that were sown with cover crops than in the control stubble plots. Data currently being gathered will reveal whether there have been any changes over winter.  With help from Agrii, we are also monitoring changes in soil moisture through the soil profile across the plots in two of the experimental fields.

Our Soil Scientist, Dr Felicity Crotty and NIAB staff gather cover crop data from experimental plots at Loddington

We also need to consider implications for the following commercial crops and will capture crop cover and yield data, as well as associated economics, across the experimental plots this autumn.  A spring oats crop in one field of cover crop plots last year delivered a yield that was about 20% higher than the bare stubble plot, sufficient to cover the costs of establishing the previous cover crop, but such benefits do not appear to follow through to the wheat crop that has followed the oats.  We need to consider implications across the rotation, rather than for individual crops, and also different crop management practices. Comparisons of cover crop destruction method (sheep grazing vs. spraying) and establishment method for the following winter wheat are on our research agenda for the coming year.  Watch this space.  We will reveal all!


  1. Only qualifies for EFA if left for full year here in NI. In Ireland much more sensible, CC overwinter then spring crop drilled qualifies !! #unfair