A Shout Out for the Worms!

Preparing to count worms

At long last we have finally managed to get some time in the field to do some worm counting.  I have been trying to find a few hours for quite some time BUT at long last we have created a bit of a benchmark.  It should have been done at the start of the switch into no-till farming but as always its not until you start something that you realise what is important and believe me-these guys are important! So what did we find out?  Firstly that there are many factors that have an effect of worm numbers.  The first field we sampled was on our sand and gravel fields with a high sand content.  

We randomly sampled 4 separate areas within the field, each sample measured 20cm wide x 20cm across and 30cm deep.  This field is only into year 2 of no-till farming and as you can see from the photograph below the worm numbers are quite low.  On this field we had an average count of 11 worms/sample section with a minimum number of 6 and a maximum number of 15.  Our target is 16 worms in a spade full, so roughly our sample size.  We measured the soil temperature as a point of reference to see, when we re-sample, what effects this might have on the population and all sample points were geo-tagged so we can return.

This field averaged out at 268 worms/m2 which is slightly short of our target population of 400 worms/m2.  So there is some work to be done!  By reduced cultivation or no-tilling our fields and by returning crop residue, or by adding compost as worm feed we should be able to build populations over a relatively short period of time.

Worm count form Bottom Heath-Sandy field

The next sample field was up on Bredon hill at an altitude of 900ft above sea level in a field planted with winter wheat, after oilseed rape (same rotation as the sandy field).  Up here the worm populations were very pleasing with some sites hitting 45 worms/sample.  Most of them were epigeic worms, which move around in the upper surface layers of the field feeding on crop residue and will help to recycle the decaying material.  The counts ranged form 12-45/sample area.

Worm count from Shaldons-Cotswold Brash

But why bother, what is the point of having more worms, what do they do for us in the middle of an arable field?

Worms are important for many reasons; their burrows aerate the soils, moving fresh air (oxygen) down into the plant rooting zone, breathing life into the deeper layers of soil.  We must not forget that soil is made up of 25% air.  Worms also feed on soil, reformatting its structure in the form of casts on the soil surface.  These casts are rich in available plant nutrients held in a stable organic state, unlikely to leach through the soil surface.  These castings can contain 7 x more phosphorus, 10 x more potassium, 5 x more nitrogen 3 times more magnesium and 1.5 x more calcium than the surrounding soils.  Recycling the dead plant material is also a key role played by these sub terrain dwellers, coming up to the surface and dragging down plant material such as straw, leaves and any organic material we may add.  They are also key when it comes to field drainage.  The burrows of Anecic worms can go down 2-3 meters which are very helpful for taking storm water down into the subsoil and stopping it running off from the fields, helping reduce flash flooding events further down the catchment.  Worms are also food for others, so a good supply can only benefit the populations of birds and small mammals increasing overall farmland biodiversity. 

Worm Cast in Shaldons

There is more to do.  I will be sampling the heavy land fields (4 years no-tillage) and some other areas of the farm that have recently been cultivated to see what numbers are lurking in the soil.  We will be looking at increasing the feed for worms to continue their growth in some areas.  Can we get too many worms or will dry summers and cold winters even out the populations?  Only time and monitoring will tell.  If you want to find out more information then please consider joining the Earthworm Society of Britain who are looking for new members and people to search for and record their worm populations.