Effects of organic farming on weed flora composition in a long term perspective 

A. Lundkvist¹, L. Salomonsson², L. Karlsson¹ and A. D. Gustavsson³

Abstract
In 1987, the Ekhaga Experimental Farm in Sweden was established on a site that previously had been subjected to conventional farming, and has been managed since then as an organic farm.

To study the effects of organic farming on weed population development and crop yields, two different crop rotations were designed, one adapted for animals (six fields) and one without animals (six fields). Each field contained a fixed 1 m² reference plot in which all the weed observations were done each year.

During the period 1988–2002, number of weed plants in spring and weed biomass at harvest were recorded in the reference plots. No differences in these two parameters were observed between the crop rotations. Number of weed plants in spring did not differ between annual crops and did not increase over the 15-year period. Neither did weed biomass at harvest nor weed species diversity change over the 15 years. The two crop rotations kept weed pressure at the same level as under the previous conventional farming practice. General field observations suggest that invasion of Cirsium arvense (L.) Scop. is occurring along the field borders.

Competitive ability of the crop showed to be important in weed regulation. Peas, a weak competitor, had significantly higher weed biomass at harvest compared with oats and winter wheat. Weather conditions during the period from April to September caused weed occurrence and development through the season to vary between years.

To improve weed management in organic farming, advisors and farmers should recognise the importance of individual field and farm analyses to design location-specific, farm-adapted crop rotations.


Source
European Journal of Agronomy (2008) 28: 570-578
DOI: 10.1016/j.eja.2008.01.001 


Author Locations and Affiliations
(1) Department of Crop Production Ecology, Swedish University of Agricultural Sciences, P.O. Box 7043, SE-750 07 Uppsala, Sweden
(2) Department of Urban and Rural Development, Swedish University of Agricultural Sciences, P.O. Box 7005, SE-750 07 Uppsala, Sweden
(3) Swedish Board of Agriculture, Dragarbrunnsgatan 35, SE-753 20 Uppsala, Sweden
* Corresponding author, E-mail Anneli.Lundkvist@vpe.slu.se


Posted November 2010