Published online by Cambridge University Press: 20 January 2017
Management practices and cropping systems that serve as integrated weedmanagement practices, and at the same time can contribute to improved soilquality, will be important for the sustainability of agricultural productionsystems. The objective of this study was to assess weed species populationdensity under contrasting tillage (conventional tillage [CT] and no tillage[NT]), residue burning (burn and no burn), and residue level (low and high)treatments after 5 and 6 yr of consistent management in a wheat–soybeandouble-crop production system. A field experiment was conducted from fall2001 to fall 2007 in the Mississippi River Delta region of eastern Arkansason a Calloway silt–loam. Weed assessments were conducted twice during thesoybean growing season, before (early season) and after herbicideapplication (late season) in 2006 and 2007. Total weed density was greaterunder CT (513 plants m−2) than under NT (340 plants m−2) early in the growing season in 2006, but was greaterunder NT than CT late in the season in 2007, suggesting that theeffectiveness of glyphosate on total weeds differs between CT and NT.Averaged across residue levels, grass species density was greatest in theNT–burn (68 to 167 plants m−2) combination and lowest in theNT–no-burn (41 to 63 plants m−2) early in the growing season inboth years. Broadleaf density was greater early (200 to 349 plants m−2) than late (18 to 20 plants m−2) in the growingseason under both CT and NT in 2006, but in 2007 broadleaf density did notdiffer by tillage treatment between seasons. Perennial weed density wasgreater in the burn (99 plants m−2) than in the no-burn (59plants m−2) treatment in 2006. No tillage, no burning, and a highresidue level appeared to contribute to the suppression of most weed specieswithout reducing herbicide efficiency.