Individual and interactive effects of crop type and management on weed and seed bank composition in an organic rotation

Document Type: Research Paper


1 Agronomy and Plant Breeding Department, Mashhad Branch, Islamic Azad University, P.O. Box 91735-413, Mashhad, Iran.

2 ADAS UK Ltd, c/o Newcastle University, NEFG Offices, Nafferton Farm, Stocksfield, Northumberland NE43 7XD, UK.

3 Nafferton Ecological Farming Group, Newcastle University, Nafferton Farm, Stocksfield, Northumberland NE43 7XD, UK.


We investigated the effects of organic and conventional pest and fertility
management on weed cover and the seed bank community in an organic rotation.
The study was conducted during the 4th and 5th years of an organic rotation on
part of a long term organic-conventional comparison trial. Results showed that
although crop type (potato vs. cabbage) in a single year significantly affected weed
functional group and cover of individual species, it did not change weed functional
group and composition in the seed bank in the following year. Five years of
organic crop protection management increased weed species that depend on
regeneration from seed and increased Ellenberg light, reaction and nitrogen values
and a seed bank persistence index in comparison with conventional crop protection
management. Three species (Chenopodium album L., Poa spp. L. and Stellaria
media (L.) Villars) that is important for biodiversity of arable fields were more
prevalent in organic protection plots. Fertility management had no significant
effects on weed seed bank composition and functional group. The additive effect of
organic practices on perennial ratio and competitor radius value was an important
finding. Organic fertility management and crop protection acted together to
increase these two aspects of the soil seed bank in comparison with other treatment
combinations and a similar effect was seen on Poa spp. L.