Weeds in field crop rotations

Abstract

The purpose of the research is to trace the dynamics of weed infestation and determine the species composition of weeds in field crop rotations, to show the impact of crop rotation, agricultural background and time on weed infestation of crops. Studies were carried out in 1998 - 2017 in the conditions of the Republic of Mari El on sod-podzolic medium-loamy soil with a high content of mobile forms of phosphorus and exchangeable potassium. The biomorphological spectrum of weed species showed that the share of juvenile weeds accounted for 26 species, perennial-9 species. During the research in the studied agrocenosis there was an increase in weed abundance: in the first rotation - 60.78 pcs/m2, in the second - 67.48 pcs/m2, in the third rotation - 75.95 pcs/m2. During the research there was an increase in the number of such annual weeds as Polygonum aviculare, Erodium cicutarium (L.), Veronica polita, Capsella bursa-pastoris, Viola arvensis, Fumaria officinalis and Stellaria media. The number of Chenopodium album and Echinochloa crus-galli increased significantly, especially in the last six years of research. Every year the infestation with Galeopsis tetrahit, Centaurea cyanus, Apera spica-venti and Amaranthus retroflexus was decreasing . The greatest annual weed infestation (71.86 pcs/m2) was in grain rotation, and the least - in grain-fodder fallow rotation (54.83 pcs/m2). The maximum number of perennial weeds was found in the I crop rotation - 14.08 pcs/m2. The variant without fertilizers showed the least infestation with annual weeds- 59.95 pcs/m2. Against the background of N60P60K60 their number increased by 8.98 pcs/m2 (LSD05 - 5.50).