Introduction

Two trials investigating the biodiversity value of selected alternative crops were established in Orkney in 2005, one on Orkney mainland (Weyland Farm) and one on the island of Sanday (Nearhouse). At each site, biodiversity was assessed in the following habitats:

• Single plots of selected alternative crops:

 

• Turnip rape (Brassica rapa),

• Bere barley (Hordeum vulgare),

• Borage (Borago officinalis),

• Echium (Echium plantagineum),

 

• Camelina (Camelina sativa).

• A single plot of wild bird cover crop.

• A willow (Salix viminalis) wind break. .

• Uncropped headland surrounding the alternative crops.

• Adjacent improved grassland.

Biodiversity at each trial site was assessed by gathering information on the following:

• Insects, bumble bees, moths and other invertebrates
• Non-crop flowering plants
• Birds and mammals

 

 

Preliminary results

Insects, bumble bees, moths and other invertebrates
Investigation found there were c90 species including yellow bumblebee (Bombus distinguendus) and heath carder bee (Bombus muscorum).
Alternative crops preferred by these species were:

• Turnip rape
• Echium
• Borage
• Wild bird crop

 

Non-crop flowering plants

Data collected on the occurrence of weeds showed that at both sites this was most diverse on the headland and amongst the more open broad-leaved crops (especially turnip rape, borage and Echium). There were limited species consisting mainly of perennial broad leaved weed species

o Buttercups
o Daisies
o Docks
o Dandelions
o Ribwort plantains

Species of interest included:

o Corn Spurrey (Red data list)
o Purple ramping fumitory (UK BAP priority species)

Observations on the phenology of crop plants in the trial showed that most were in flower in July and August. Potentially valuable plants for earlier flowering are turnip rape and mustard (in the wild bird cover) while borage, linseed and Phacelia flowered into September and Echium right up to October.

 

Birds and mammals

Investigation found over 20 species of birds on the plots including Linnets, Swallows, Rock doves, Skylarks and various other species. Although birds tended to move freely between the different plots, there was a suggestion from the observations at Nearhouse that, amongst the alternative crops, borage and Echium were particularly attractive with Chaffinches, Skylarks, Linnets and Redwings seen amongst the remnants of the crops in March 2006. No mammals were recorded on the trials.

 

Initial conclusions

• Several alternative crops can make a very positive contribution to promoting insect biodiversity compared with improved grassland.

• The more open crops and headlands also had a more diverse weed flora than improved grassland.

• At the Sanday site, in particular, the unharvested crops, particularly borage and Echium, attracted a range of seed-eating birds through the winter, indicating that some of these could be a useful addition to wild bird cover crop mixes.