The impact of changing the season in which cereals are sown on the diversity of the weed flora in rotational fields in Denmark

Abstract

Summary 0[ Surveys have shown that there has been a dramatic decrease in the weed~ora of _elds under rotational cultivation during the last 29 years[ This trend has been particularly noticeable in winter cereals\ a crop of increasing importance in the landscape[ 1[ The weed~ora of spring and winter cereals was compared in 08 unsprayed _elds during a 4!year study to test the hypothesis that cereal type exerts no e}ect on thẽ ora or on the absolute and relative abundance of single species[ 2[ Plant and species densities\ and accumulated species richness\ were lower in winter than in spring cereals[ 3[ Floristic similarity was greater among spring cereal _elds and between spring and winter cereals within the same _elds than among winter cereal _elds[ 4[ Species that occurred with unequal density in spring and winter cereals occurred at higher densities in the spring cereals^these species germinated mainly in the spring[ However\ for a few species the relative plant abundance was highest in winter cerealst hese species were able to germinate both in the spring and autumn[ 5[ Some species Ð on the relative scale Ð occurred indi}erently of season of sowingâ ll but one of these species were able to germinate both in the spring and autumn[ 6[ Plant species and taxa that are important food resources for arthropod herbivores occurred at greater densities in spring than in winter cereals and\ in addition\ occurred with the highest relative abundance in spring cereals[ 7[ Change in land use from spring to winter cereals involves not only an immediate reduction of more than 14) in the density of plants and species\ but also a change and increased uncertainty in the composition of the weed~ora[ These _ndings may have serious implications for the ecology of wildlife in the agricultural landscape[ Key!words] farmland\~oristic diversity\ plant density\ species density\ wild plants[ Journal of Applied Ecology "0888# 25\ 13Ð21

Contrasting weed species composition in perennial alfalfas and six annual crops: implications for integrated weed management

“…Roberts, 1984;Hald, 1999;Fried et al, 2008). Weed communities in rape crops (sown between August and October) were characterised by species preferentially emerging in autumn or late summer including Euphorbia helioscopia, Sinapis arvensis and Viola tricolor.…”

Management options for the conservation of rare arable plants in Europe

“…Over the course of the 20th century, synthetically produced herbicides and fertilizers radically changed the situation, enabling much more efficient weed control, more densely-planted and more competitive crops, and narrow rotations made up of just a few profitable crops. In cereal cultivation, shifts occurred from spring cereals towards winter cereals (Hald 1999a;Takács-György and Takács 2012), as well as towards earlier cultivation of cereal stubble . With the rise of chemical weed control, inversion tillage by means of ploughing was frequently replaced by reduced non-inversion tillage, or even no tillage (Chancellor, Fryer, and Cussans 1984;Cannell 1985;Morris et al 2010).…”

Weed Problems, Ecology, and Management Options in Conservation Agriculture: Issues and Perspectives

“…Surveys have shown that there has been a dramatic decrease in the weed density (Teasdale et al, 2004) and flora of fields under rotational cultivation (Hald, 1999). Effectiveness of a short-term management decision depends on the choice of the rotation and its elasticity patterns.…”