The effect of crop diversification in small fields on the community of natural enemies on the ground: A strip cropping experiment with white cabbage in the Netherlands

Abstract

Agricultural development has contributed significantly to the decline in biodiversity over the last century. Crop diversification is promoted as a strategy to mitigate this ongoing catastrophe. This study investigates the effects of strip cropping as a means of crop diversification on the activity density of ground dwelling natural enemies and the composition of ground beetles. Natural enemies were captured by placing pitfall traps in a cabbage crop over the course of three years. Although several studies have shown a positive effect of crop diversification on biodiversity and the abundance of natural enemies, in this study no such effect was detected. A possible explanation might be that the surface designated to each treatment was smaller than 0.28 hectares and located in a diverse landscape (with e.g., an abundance of semi-natural habitat and field edges). Therefore, the treatments were probably already exposed to a diversity and an abundance of ground-dwelling natural enemies, making potential effects of crop diversification on small fields relatively marginal and thus, below the detection limit. Yet, the results could also be an indication that applying crop diversification in larger fields may have a greater impact on ground dwelling natural enemies than in small fields (<0.28 ha).