Die Bedeutung verschiedener Ackerrandtypen für das Vorkommen und die Phänologie von Wildkräutern unter konventionellen und biologisch-organischen Anbaubedingungen

Summary

In 1989, we investigated the arable weed vegetation on conventionally and organically farmed but otherwise fully comparable barley fields and their connecting meadow and wood habitats near lake Ammersee (Upper Bavaria). Special attention was paid to species diversity, weed coverage, distribution, and phenology on inner and outer field edges.

Organic farming led to fairly higher degrees of species diversity, to a natural development of weed cover degrees during the growing season due to being cut during harvest time only, not affected by occasional herbicide impacts, and to intensively fructifying weeds.

Weeds found on the conventionally farmed field mostly occurred in surrounding habitats, too; while 35 of 46 weed species growing in the organically farmed field were restricted to the field itself.

From among the surrounding habitats, only an extensively used meadow with newly planted small trees and bushes was found to be a refugium for arable weed species. Fructification on this area of only 0.5 ha had double the generative reproduction success of the neighbouring 6 ha conventionally farmed barley field.

Local weed distributions were used to differentiate between ecological weed groups prefering field, fallow strip, meadow, wood habitats, and the ecotones between. Weed fructification on the conventionally farmed field mostly could be completed only at field edges where the barley suffered from failing fertilizers more than arable weeds did from herbicide impacts.

Strips adjacent to fields or weedy and grassy edges of hedges and small woods should be mowed irregularly, both to promote annual arable weed species, which prefer low and sparse vegetation during the year, but also to enable fructification of perennial species in another.