Hidden benefits of grass margins

We know from our previous research, and from other studies, that earthworms and other soil organisms are essential to soil functions that influence crop performance, water quality and flood control.  Our research has also shown that these organisms benefit from stable soil conditions associated with reduced tillage and no-tillage systems of crop establishment.  Soil life is enhanced by crop rotations in which the soil is not disturbed.

Desirable though this might sound, achieving these conditions is not so straight forward.  At some stage in the rotation, it might be necessary to plough for root crops, or because of wet conditions or for weed control for example.  The biological communities in the soil are rapidly destroyed and organic matter mineralised following cultivation.

Pasture provides a refuge for soil organisms such as earthworms but is not present or sufficiently well distributed on many farms.  On these farms, grass margins created under Environmental Stewardship schemes may provide an alternative refuge from which colonisation of arable soils can take place.

Worm numbers in grass margin and along transects through arable fields

MSc student, Stephen Jones recently completed his research into this issue in our School Farm catchment.  Worm numbers, biomass and species richness were all greater in grass margins than in the adjacent wheat or first year grass ley fields, with values for the first metre inside the field being consistently intermediate between those of the margin and main field.  There was a higher density of worms in fields next to Environmental Stewardship margins than in fields next to narrower cross-compliance margins.

These findings are important as they suggest that grass field margins, especially those created within Environmental Stewardship schemes, serve as a potential reservoir for recolonisation of arable fields when worm numbers become depleted by intensive cultivation.  The same may be true for other soil organisms.  Given the importance of earthworms and other soil organisms for soil function, including crop rooting capacity, nutrient cycling, water quality and flow control, the benefits of grass margins may be considerably greater than has formerly been assumed.