The Impact of Integrated Farming Systems on Arable Weed Floras.

Abstract

This was a bolt-on study to the LINK Integrated Farming Systems Project and aimed to focus on aspects of integrated weed management using small plot trials. A three year rotation experiment indicated that the greatest influence on weed biomass and species composition was time of drilling. The earliest sown crop, winter oilseed rape, contained the greatest weed biomass. Weed biomass was lower in winter wheat sown in September and least in wheat sown in October. Weed species composition varied with time of drilling and the effect was seasonal. Winter sown wheat cultivars differed in their competitive ability; Tonic contained less weed biomass than Spark. Winter oilseed rape, spring oilseed rape and spring barley did not exhibit cultivar differences.
A row spacing x density trial examined the effect of increasing row width on weed abundance. Sown late in spring, the winter cultivar Spark was unvernalised and tillered more profusely than spring cultivar Tonic. Tillering capacity was poorly linked with weed suppression. Tonic matured earlier creating greater shading and temporal differences in light interception that were linked to lower weed presence. Weed biomass was not affected by row width but was reduced by increasing crop density. At the combination of row widths and densities used, yields were reduced at the highest density with wide rows.
The effects of reduced rate herbicide applications on the seed production of non-target weed species was studied. Fluroxypyr reduced the average seed weight of V. persica at half the recommended rate. Cultivar was also seen to affect average seed weight.
The use of reduced herbicide dose was examined in combination with mechanical weeding. An experiment in spring barley compared full rate herbicide use with a 20% herbicide dose and one pass with a mechanical weeder. There was no difference in weed control ability between these two methods.