Effects of crop rotation and soil tillage on weeds in organic farming

Abstract

An organic long-term field experiment with two factors has been carried out since 1998 at the experimental station Gladbacherhof, University of Giessen. Effects of 3 different farm types (with lifestock raising, stockless farming with rotational set-aside, stockless farming only cash crops) combined with 4 tillage treatments (mouldboard plough, two-layer-plough, reduced tillage depth and tillage without plough) on plants, soil and environment have been investigated. This article presents results on the coverage rate of arable wild plants (weed coverage), the range of weed species, the abundance of C. arvense (L.) Scop. (Canada thistle) and the weed phytomass during harvest time of the main crops dependent on farm type and soil tillage. It can be concluded that, compared to conventional economic weed thresholds, the weed coverage was generally relatively low and only limited ranges of species were found. Wild arable plants probably did not have any impact on yields of the cultivated plants due to intensive mechanical regulatory measures. In stockless organic farming without alfalfa-grass in the crop rotation Cirsium arvense (L.) Scop. (Canada thistle) might become a problem whereas this perennial root-weed does not seem to raise a long term problem in a soil tillage system without ploughing. In all treatments the abundance of weeds like Galium aparine L. (catchweed bedstraw) and Stellaria media L. (chickweed) was high. However, none of the farm types or soil tillage systems succeeded in providing evidence of promoting rare species or encouraging biodiversity. In order to achieve this special support measures should be implemented.

Keywords

• crop rotation
• organic farming
• range of species
• segetal flora
• soil tillage
• weed coverage