The behavior of weed seed bank to different tillage and residue mulch treatments after three years of cropping in Bangladesh

A three-year (2012 - 2015) longer wet rice-wheat-jute crop rotation experiment was sampled from the Rajbari district of Bangladesh. The objective was to study the effects of strip tillage (ST), bed planting (BP), and zero tillage (ZT) relative to conventional tillage (CT) with increased residues (20 vs. 50%) of previous crops on the composition of soil weed seed pool. The weed abundance at 0-15 cm soil profile was quantified following “seedling germination method” at the green-house of Bangladesh Agricultural University during January - December 2016. The year-round count of germinated weeds revealed the fewest number of species, and the lowest density of broadleaf, grass, and sedge weeds were found in ST, followed by CT, BP, and ZT with 50% crop residues. The diversity of weed flora having some specific weeds was the least at ST but the ZT was the most diversified followed by BP and CT. The ST plus 50% residue decreased the weed composition. Still, they increased the relative proliferation of perennial weeds compared to CT. Weed composition in ST was even smaller than BP and ZT. The ST, BP, and ZT enriched the abundance of perennial weeds: Alternanthera sessilis, Leersia hexandra, Dentella repens, Jussia deccurence, Solanum torvum, Hedyotis corymbosa. On the other hand, annual weeds: Euphorbia parviflora, Cyperus iria, Monochoria hastata, Digitaria sanguinalis, Lindernia antipoda, L. hyssopifolia and Fimbristylis miliacea were dominated the weed seedbank at 0-15 cm soil profile after three years of cropping in Bangladesh.