Individual study: Arthropod abundance was higher following conservation tillage than conventional cultivation in Germany
Heimbach U. & Garbe V. (1996) Effects of reduced tillage systems in sugar beet on predatory and pest arthropods. Arthropod Natural Enemies in Arable Land, Wageningen (Netherlands), 71, 195-208.
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A replicated, controlled study of two fields on two farms in Saxony, Germany from 1991 to 1992 (Heimbach & Garbe 1996) found that conservation tillage plots (with catch crops of phacelia Phacelia tanacetifolia or white mustard Sinapis alba) without seed-bed preparation in the spring resulted in an increase in spiders (Araneae), rove beetles (Staphylinidae) and ground beetles (Carabidae). Spider and ground beetle density was higher in conservation tillage plots without tillage in spring (spiders: 32-85/m², ground beetles: 6-21/m²) compared to those with tillage (15-38, 2-14/m² respectively). However rove beetle abundance differed between catch crops: rove beetles no tillage: 70-95/m² in phacelia, 54-100/m² in white mustard; tillage in spring: 50-83/m² in phacelia, 84-148/m² in white mustard. Plots with conservation tillage had higher numbers of all three taxa than conventional plots (spiders: 10-18/m², rove beetles: 43-62/m², ground beetles: 2-11/m²). Numbers tended to be higher when white mustard was used compared to phacelia, particularly for ground beetles (4-21 vs 2-17/m²). Fields were divided into plots (12-24 x 100 m) with two replicates of five soil cultivations: conventional (ploughed, tillage, drilling of sugar beet Beta vulgaris) or conservation tillage with phacelia or white mustard (ploughed, tillage and drilled) followed by soil tillage and drilling or direct drilling of sugar beet in spring. Insecticides were not applied where predatory arthropods were monitored. Two ground photo-eclectors with a pitfall trap were used in each plot and were emptied and moved 1-2 times/week from sugar beet drilling until the end of June. Pest data are not included here.