Conservation value of the herbaceous vegetation in hedgerows - does organic farming make a difference?

Summary

The aim was to compare and test differences in the conservation value of hedge bottom vegetation on organic and conventional farms. The studied hedgerows (28 organic and 28 conventional) were on average 14 years old and established in the same way, except that organic hedgerows were established and managed without use of pesticides. We investigated three sample plots of 10 m2 in all hedgerows together with a set of 13 explanatory variables. There were no differences in soil texture between hedgerow types but organic farms had higher pH and lower conductivity. Organic farms had higher total N values, which are explained by a slightly higher content of organic matter. There was highly significant interaction between farming type and neighbouring crop type according to soil phosphate concentration. Significantly more plant species were found in the organic hedgerows. The species compositions in organic hedgerows appeared significantly more similar to semi-natural communities when compared with other plant communities. We conclude that organic farming is slightly superior with regard to conservation of herbaceous diversity of hedgerows in intensively cultivated agricultural landscapes. The possible reasons for this are discussed.