Biodiversity of weed communities in common wheat and spelt following various forecrops

Environmentally-friendly solutions are increasingly often applied in crop cultivation technologies. These include, among others, the return of old crops (e.g., spelt wheat) and crop rotation. Ensuring a proper forecrop is essential, especially in the cultivation of winter wheat, which is susceptible to infestation by weeds. However, there is only sparse information on infestation by weeds in the cultivation of winter spelt. In this study, it was assumed that this crop is invaded by weeds to a lesser extent than wheat, especially after unfavorable forecrops. The study was based on a field experiment conducted in the east part of Poland. The aim was to compare the weed infestation of common wheat and spelt wheat grown after peas, oilseed rape, and after itself. Analyses of weed infestation were conducted in 2014–2016. The weed species composition and population size were determined as well as their dry weight. The following indices were calculated: index of species richness, Simpson’s domination index, Shannon–Wiener index of species diversity, and Pielou’s index of evenness. The weed infestation of spelt wheat was higher than that of common wheat during the tillering stage. It was similar in both species during the heading stage. The lowest weed infestation in both cereals was observed on a field where peas had grown. Growing after oilseed rape and after themselves contributed to an increase in weed infestation. Biomass of weeds in a field of spelt was similar after all forecrops, unlike that in wheat, where more biomass was observed after oilseed rape and wheat. A greater share of Apera spica-venti and Viola arvensis was observed in common wheat and spelt grown after oilseed rape and after themselves. Weed communities in spelt were more diverse than in wheat. The forecrops did not differentiate the species diversity in either crop.