Spring 2010 worm counts comparing a ploughed field with direct drilling

April 23, 2010

Two fields were compared, Hornfield – ploughed and power harrowed, sown to winter wheat, and Cobb Hill – direct drilled to OSR.  Both fields have reddish brown slightly stony silty clay loam soils with coarse prismatic or blocky subsoils.

Worm counts were carried out using the Visual Soil Assessment method (Landcare Research, 2000).  Numbers of worms in a 20cm3 soil sample were counted over a 5 minute period.  Penetrometer readings were taken to assess soil compaction at each sample site and a visual note of soil structure in each soil sample was made.  Five sample sites were tested in each field.

The results below include the penetrometer readings taken in Cobb Hill in October 2009 for comparison.

Average penetrometer readings (MPa)

at depth:



April 2010

(Ploughed and power harrowed. Planted with winter wheat)

Cobb Hill

April 2010

(Direct drilled to OSR)

Cobb Hill

October 2009

(Direct drilled to OSR)

5 0.5 1.4 1.4
10 0.6 1.7 2.1
15 0.7 1.7 2.7
20 1.0 1.8 2.8
25 1.4 1.9 3.0
30 1.7 2.3
35 2.1 2.6
40 2.4 2.7
45 2.6 3.0
Average number of worms in 20cm3 soil

(range 2 – 20)


(range 29 – 43)

per m3 equivalent 315 860


Topsoil structure in Hornfield was coarsley granular but rather wet and easily smeared.  The subsoil became increasingly compacted with depth but had a good blocky structure.  Numbers of worms in each sample were variable, the worms were rather small in size and were found in the upper 20cm of the soil profile.

The soil on Cobb Hill was compacted, especially below 10 cm depth.  The majority of the worms found were in the top 10cm of the soil profile where the soil structure was good, coarse granular.  Below 10 cm depth the soil formed a typical argillic clay enriched B-horizon, generally having a coarse prismatic or blocky structure but with horizontal plates in parts.

General analysis / comment:

There is a clear difference in worm numbers between the two fields, with much higher numbers of worms in the direct drilled field.  This is probably because of the previous year’s crop debris (organic matter) available in Cobb Hill (direct drilled) for the worms to feed on.  Organic matter from the previous year’s crop debris has been ploughed in in Hornfield.  Cultivations carried out in Hornfield will also have disturbed the worm ecosystem, reducing numbers.

Soil structure in the two fields reflects management.  Hornfield (ploughed and harrowed) has a much looser soil structure compared with Cobb Hill (direct drilled) with little compaction until below 30cm depth.  Previous examination of Cobb Hill had already identified the soil compaction in this field, and the apparent easing of the compaction between the October and April readings will be because of the increase in moisture content in the soil after the winter (which allows easier penetration of the penetrometer) and not a reduction in the soil density.

The higher worm population in Cobb Hill will be responsible for the good soil structure in the upper 10cm of the soil profile and their activities will be increasing organic matter content so increasing the moisture and nutrient retaining capacity of the topsoil.  However the compaction lower down the soil profile will be reducing the potential of the crop roots to exploit the full depth of the soil profile.  A point for debate is whether the increased worm population in Cobb Hill and the improvement they will make to the topsoil makes up for the compaction and reduced root exploitation lower down in the soil profile.

Dr. Nancy Oakes conducting a worm count

Start of Soil Structure Survey

August 26, 2009

Whilst not the top of the list of topics to talk about in the pub or at the dinner table, soil structure and organic matter content are vital parts of successful arable farm.  For hundreds of years this farm has used the plough to turn over soil prior to establishing a crop and it has proved highly successful.  Ploughing buries crop residue and weed seeds, removes ruts and compaction and releases nitrates which help the new crop to grow.  However with the rise of the price of diesel and steel, ploughing is now quite an expensive option so many farmers have moved to, or experimented with, ‘min-till‘ or ‘no-till‘ techniques.  As I have mentioned in a previous blog we bought a Claydon Direct Drill last year so have exactly one years experience of not ploughing but drilling directly into stubble.  One claimed benefit is that yields should not drop or possibly even increase.

I will post the results at the end of the harvest ! In addition non inversion tillage (not turning soil over) should increase surface organic matter and worm numbers.  Organic Matter levels are hard to measure so I thought it would be easier to monitor worm type and levels.  Dr Nancy Oakes has kindly agreed to do an informal study and visited the combine on August 14th to see how things were going and talk about how to start studying soil structure and worm levels when drilling starts in a few weeks.  We will also compare the results with fields that have been planting after the plough.

Business Property Available

There are a number of High Quality Offices and Workshops available in the Business Centre now, from only £75 a week
see more »

The Old Dairy

Three Bedroom Cottage comprising of the oldest wing of the newly restored 17th century Hawthorns Farmhouse.
see more »