Response of common cocklebur (Xanthium strumarium L.) emergence and competition with corn (Zea mays L.) to seed burial depth and mulch

Common cocklebur (Xanthium strumarium L.) is a summer annual weed of the corn fields in the north-western parts of Iran. Field experiments were conducted in 2013 and 2014 to examine the seedling emergence and growth of common at different achene (seed) burial depths (3, 6, 9, 12, 15 and 18 cm) and wheat straw mulch amounts (0, 1.5, 3.0 and 4.5 ton ha(-1)). Results indicated that increasing achene burial depth and mulch amount reduced X. strumarium seedling emergence. In both years, no seedling emergence was observed from 18-cm achene burial depth. X. strumarium biomass and achene number per plant were affected by achene burial depth and mulch amount, and were greater in 2014 than in 2013. The corn leaf area index (LAI) and grain yield were higher in the treatments which deeper achene burial depth and mulch amount were high. Therefore, X. strumarium emergence in the corn can be suppressed by a tillage that buries the achenes to >= 18 cm of soil depth. Maintaining a thick residue cover will provide competitive advantage of corn over X. strumarium due to an inhibitory effect on X. strumarium emergence and growth and may lead to a reduction in the future weed infestation.