Conservation headlands for rare arable weeds: The effects of fertilizer application and light penetration on plant growth

Abstract

In addition to promoting agricultural wildlife in general, conservation headlands may be a method of providing a refuge to endangered arable weeds. The conservation headland technique excludes herbicide and insecticide use in the outer 2–3 m of the arable field, but does not restrict fertilizer inputs. We studied the effects of fertilizer application on the weed vegetation in relation to light penetration in three crop edges in the vicinity of Wageningen, The Netherlands. Furthermore, the growth response of five endangered arable weeds to different fertilizer treatments and light penetration levels was examined. Species richness and weed growth were significantly reduced in the fertilized crop edges but individual species showed both significant increases and decreases. In the fertilized crop edges, light penetration was directly related to weed performance, limiting species richness and plant growth of both the total weed vegetation and individual species, while in the unfertilized crop edges no such relation existed. Likewise, light penetration proved to be the most important correlate of plant growth of all five endangered arable weeds. Assuming that biomass production is closely related to seed production, fertilizing conservation headlands will result in reduced viability of populations of rare weeds. If preservation of rare arable weeds is one of the main goals of conservation headlands, cessation of fertilizer inputs may be required.