Individual study: Effects of headland management on invertebrate communities in cereal fields.
Hassall M., Hawthorne A., Maudsley M., White P. & Cardwell C. (1992) Effects of headland management on invertebrate communities in cereal fields. Agriculture, Ecosystems & Environment, 40, 155-178
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Create uncultivated margins around intensive arable or pasture fields
A replicated study in 1988 in East Anglia, UK (Hassall et al. 1992) found that ground beetles (Carabidae), true bugs (Heteroptera) and spiders (Araneae) were more abundant in uncropped headlands than cropped conservation (restricted pesticides) and conventional headlands. For each group, significantly more individuals were found in uncropped headlands (average number of individuals per site; spiders: 210; ground beetles: 260; true bugs: 50) than in conservation or sprayed headlands or in crops (spiders: 100-110; ground beetles: 70-160; true bugs: 15-30). Ground beetles were twice as abundant in crops adjacent to uncropped and conservation headlands than adjacent to sprayed headlands. Numbers of species were higher in uncropped headlands (ground beetles: 21 species; true bugs: 5; spiders: 26) than conservation and sprayed headlands (ground beetles: 15-18 species; true bugs: 2-3; spiders: 15-17). Spider diversity was significantly higher in uncropped (Simpson’s index: 6) than conservation and sprayed headlands and in the crop (2-3); ground beetles (4-8) and true bug (1-3) diversity did not differ. True bug nymphs Nabis ferus penetrated further into crops adjacent to uncropped and conservation headlands than sprayed headlands. Headlands represented the outer 6 m of eight barley fields at three locations. Parallel grids of 6 x 50m were set up in the headlands and the crop (8-14m from the headland), and sub-divided into fifteen 10 x 2 m sections. One pitfall trap was placed in each section (15 traps/grid). A further 2 x 50m grid was set up in the verge parallel to the field margin and divided into five 2 x 10m sections (5 traps/grid). Traps were emptied after 14 days in June-July 1988. A Dietrick Vacuum sampler was used along five transect lines (0-15 m into the crop), two samples consisting of five subsamples (each 0.4 m²) were taken three weeks apart.