Weed populations in maize as affected by crop rotation and primary soil tillage

Abstract

A seven year field study was conducted in south-western Slovakia to investigate the effects of different soil tillage intensities and crop rotation patterns on weed density, weed species composition and diversity, and weed competition in maize. Maize was grown in four different crop rotations with three different soil tillage systems (conventional ploughing, 0.3 m depth; offset disc ploughing, 0.15 m depth; shallow loosening, 0.1 m depth). Dominant weed species were Amaranthus retroflexus L., Chenopodium album L., Echinochloa crus-galli (L.) P.Beauv., Convolvulus arvensis L. and Cirsium arvense (L.) Scop. Conventional tillage reduced weed density significantly, primarily through the reduction of perennial weeds. Significantly lower weed dry biomass was observed under conventional ploughing than under reduced tillage by offset disc ploughing or shallow loosening. Crop rotation did not have a significant influence on species richness as indicated by the Margalef's index. However, there was significantly higher total weed density in continuous maize cropping (38.5 plants m-2) than when maize was grown in rotation with spring barley (28.6 plants m-2) or in rotation with peas and winter wheat (25.8 plants m-2). Primary tillage systems had a more significant effect on the composition of the weed flora, weed density and diversity, and weed biomass than did crop rotation patterns.