Companion cropping trial

29 May 2024

Members of the Biomass Connect team have been in the field hand-sowing seeds as part of a small trial to explore the potential of using companion crops within willow SRC to aid growth, suppress weeds and benefit biodiversity, led by Dr Rebecca Rowe of UKCEH.

The trial is testing the potential of six different plant species, to act as companion crops both during crop establishment and in mature crops using three sites, two newly established, and one mature plantation.

The six different plant species (Table 1) have been selected based on balancing a combination of the availability and cost of the seeds, the rate of growth and plant height (to prevent direct competition with the newly planted willow), the potential to support willow growth by nitrogen fixation or weed suppression, level of shade tolerance, and potential to provide biodiversity benefits.

The team have been out hand-sowing small 5 m long plots within the wheel line between the willow trees, with sowing completed at two of the three planned sites.  The plots will be monitored over the summer and autumn for companion plant survival, biomass production and composition, and weed suppression with a final report due in the winter.

Table 1.

SpeciesAnnual or perennial speciesN fixing/ecosystem benefits
Yellow trefoil (Medicago lupulina)AN fixing, pollinator-friendly, recommended for broadcast under sowing in cereals for weed suppression.
Bird foot trefoil (L. corniculatus)AN fixing, pollinator-friendly
Alsike clover (Trifolium hybridum)PN fixing, pollinator-friendly, limited persistence after 2-3 years, but selected due to greater shade tolerance and slow-growing nature than other clovers.
White small Clover (Trifolium repens)PN fixing, pollinator-friendly, low growing.
Rib leaved plantain (Plantago lanceolata)PDeep roots can aid soil structure, seeds sources for birds, good weed suppression potential
Self heal (Prunella vulgaris)PPollinator-friendly,  good weed suppression potential

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