Rotational fallows in support of functional biodiversity

Published source details Huusela-Veistola E. & Hyvanen T. (2006) Rotational fallows in support of functional biodiversity. IOBC/wprs Bulletin, 29, 61-64.
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This study is summarised as evidence for the following.

	Action	Category
	Create rotational grass or clover leys Action Link
	Leave overwinter stubbles Action Link
	Provide or retain set-aside areas in farmland Action Link

Create rotational grass or clover leys

A controlled trial from 2003 to 2004 in Jokioinen, southern Finland (Huusela-Veistola & Hyvanen 2006) found that fallow plots established by undersowing spring barley with grass or grass and red clover Trifolium pratense had more spiders (Araneae) and fewer pest insects than a control plot of spring barley, but similar numbers of ground beetles (Carabidae). For example, there were 28-35 spiders/ trap, compared to around 5 spiders/trap in the control plot. The only difference between seed mixtures used was that the plot sown with red clover in the mix had fewer unsown plant species (around 2 species/m²), but higher plant biomass, than control cereal fields, which had around 16 plant species/m². The plot undersown with just grasses had around 6 plant species/m². There was no difference in the numbers of spiders, beetles, flying insects or unsown plant species, between two year grass or grass-clover fallow plots established by undersowing spring barley, and similar plots sown without accompanying cereals. The fallow treatments were established in 2003, each on a 44 x 66 m plot. A control plot was sown with spring barley in 2004. Insects were sampled using a yellow sticky trap and three pitfall traps in the centre of each plot for a week in June, July and August 2004. Unsown plant species were counted in four 50 x 50 cm quadrats in each plot in late August 2004.
Leave overwinter stubbles

A controlled trial from 2003 to 2004 in Jokioinen, southern Finland (Huusela-Veistola & Hyvanen 2006) found that uncultivated barley stubble had significantly more spiders (Araneae) than a control spring barley crop, but similar numbers of ground beetles (Carabidae) and unsown plant species. The stubble field had around 20 spiders/trap, compared to around five spiders/trap in the control plot. A 44 x 66 m plot of uncultivated spring barley stubble was established in 2004 (the barley sown and harvested in 2003), and compared with an equivalent plot of spring barley crop sown in 2004. Insects were sampled using a yellow sticky trap and three pitfall traps in the centre of each plot for a week in June, July and August 2004. Unsown plant species were counted in four 50 x 50 cm quadrats in each plot in late August 2004.
Provide or retain set-aside areas in farmland

A controlled trial in Jokioinen, southern Finland (Huusela-Veistola & Hyvanen 2006) from 2003 to 2004 found more spiders (Araneae) and flying insects in set-aside than in a control cereal crop, but not more plant species or ground beetles (Carabidae). Spiders were significantly more abundant in two-year fallows, regardless of the sowing treatment (28-55 spiders/trap) than in one year fallows, in which spider numbers did not differ from the control cereal crop (less than 10 spiders/trap). Numbers of flying insects in the vegetation followed a similar pattern, with fewer insects in first year fallows than in stubble or two -year fallows. Numbers of ground beetles and numbers of plant species were similar across all fallow treatments and in the case of beetles, also in the control cereal crop (5-25 beetles/trap, 2-14 unsown plant species/m²). Two-year fallow plots sown with red clover had fewer plant species (around 2 species/m²) than control cereal fields, which had around 16 plant species/ m². Fallow treatments were established in 2003 or 2004, each on a 44 x 66 m plot. The treatments were: one- and two-year fallow sown with either grasses, or a grass- red clover Trifolium pratense mix; two-year rotational fallow established by undersowing spring cereal with either grasses, or a grass-red clover mix. The control was a spring barley crop. Insects were sampled using a yellow sticky trap and three pitfall traps in the centre of each plot for a week in June, July and August 2004. Unsown plant species were counted in four 50 x 50 cm quadrats in each plot in late August 2004.